science units grade 6 · 6l.2 harmful micro-organisms 217 6m.2making pure substances from mixtures...

Science units Grade 6

Contents

6L.1 Cells 211 6M.1 Solubility 241 6P.1 Different kinds of forces 273

6L.2 Harmful micro-organisms 217 6M.2 Making pure substances from mixtures

247 6P.2 Light 281

6L.3 Classification 223 6M.3 Changing materials 253 6P.3 The effects of forces 289

6L.4 Teeth and eating 229 6M.4 Heating and burning 259

6L.5 Organs and systems 235 6E.1 Movement of the Earth and the Moon

265

Science scheme of work: Grade 6 units 107 hours1st semester55 teaching hours

Unit 6L.0: Preliminary unitIntroduction to grade and revision ofkey ideas from previous grades.1 hour

Life science: 19 hours Materials: 14 hours Physical processes: 9 hours

Unit 6L.1: CellsPlant and animal cell structure. Tissuesand organs.6 hours

Unit 6L.2: Harmful micro-organismsCommon illnesses caused by micro-organisms. Spoiling of food.6 hours

Earth and space: 13 hours

Unit 6M.0: Preliminary unitIntroduction to grade and revision ofkey ideas from previous grades.1 hour

Unit 6M.1: SolubilityDifferences in solubility. Uses ofdifferent solvents.7 hours

Unit 6P.0: Review unitIntroduction to grade and revision ofkey ideas from previous grades.1 hour

Unit 6P.1: Different kinds of forcesContact forces and forces that act at adistance. Gravity. Mass and weight.8 hours

Unit 6P.0: Preliminary unitIntroduction to grade and revision ofkey ideas from previous grades.1 hour

Unit 6E.1: Movement of the Earth andthe MoonPhases of the Moon. Day and night.Seasons. Tides. Eclipses.12 hours

Unit 6L.3: ClassificationMajor groups of animals and plants.Using branching keys.6 hours

Unit 6M.2: Making pure substancesfrom mixturesRecovery of the solute and solvent.Everyday examples of filtration.6 hours

Science scheme of work: Grade 6 units 107 hours2nd semester52 teaching hours

Unit 6.R: Review unitRevision of key ideas from firstsemester.1 hour

Life science: 17 hours Materials: 17 hours Physical processes: 18 hours

Unit 6L.4: Teeth and eatingDigestive system. Teeth and toothdecay.8 hours

Unit 6L.5: Organs and systemsFunction of human organs. Puberty andreproductive organs. Organs of plants.Structure of a flower.8 hours

Earth and space: 0 hours

Unit 6M.R: Revision unitRevision of key ideas from firstsemester.1 hour

Unit 6M.3: Changing materialsChemical change. Reversible andirreversible changes.9 hours

Unit 6P.R: Review unitRevision of key ideas from firstsemester.1 hour

Unit 6P.2: LightPropagation, absorption and reflectionof light.11 hours

Unit 6M.4: Heating and burningBurning and action of heat onsubstances. Temporary and permanentchanges.7 hours

Unit 6P.3: The effects of forcesForces and changes of shape andmovement. Terminal velocity.6 hours

211 | Qatar science scheme of work | Grade 6 | Unit 6L.1 | Life science 1 © Education Institute 2005

GRADE 6: Life science 1

Cells

About this unit This unit is the first of five units on life science for Grade 6.

The unit is designed to guide your planning and teaching of lessons on life science. It provides a link between the standards for science and your lesson plans.

The teaching and learning activities should help you to plan the content and pace of lessons. Adapt the ideas to meet the needs of your class. For extension or consolidation activities, look at the scheme of work for Grade 7 and Grade 5.

You can also supplement the activities with appropriate tasks and exercises from your school’s textbooks and other resources.

Introduce the unit to students by summarising what they will learn and how this builds on earlier work. Review the unit at the end, drawing out the main learning points, links to other work and 'real life' applications.

Previous learning To meet the expectations of this unit, students should already know that living organisms require air, food and water, and that they release waste. They should already know that they are sensitive and that they grow and reproduce to create more organisms like themselves.

Expectations By the end of the unit, students know that cells are the fundamental building blocks of living organisms and that cells can have specialised features for specific functions. They use specialised equipment correctly, including a simple microscope.

Students who progress further describe and draw typical animal and plant cells, know the function of cell structures and relate the function of specialised cells to their structures. They know that cells form tissues and organs. They use a microscope, prepare a slide and examine objects such as root hairs and leaf structure.

Resources The main resources needed for this unit are: • magnifying glasses, binocular microscope, microscopes with low- and

high-power lenses • microscope that can project an image onto a screen • prepared slides of insects, hair, feathers, etc., and a variety of specialised

cells and tissues, including a transverse section of a leaf

Key vocabulary and technical terms Students should understand, use and spell correctly: • microscope, magnification • cell membrane, cytoplasm, nucleus, cell wall • muscle, xylem, phloem, palisade • tissue, organ

UNIT 6L.1 6 hours


Standards for the unit

6 hours SUPPORTING STANDARDS

Including Grade 5 standards CORE STANDARDS

Grade 6 standards EXTENSION STANDARDS

Including Grade 7 standards

6.5.1 Know that living things are made up of cells. 7.7.1 Describe and draw typical animal and plant cells …

6.5.2 Know that cells have cytoplasm, a nucleus and a cell membrane and that plant cells have a cell wall.

7.7.2 Recognise and know the function of the cell nucleus, cell membrane, cytoplasm, vacuole and cell wall …

5.6.1 Know that living organisms require air, food and water, and that the release waste; know that they are sensitive and that they reproduce to create more organisms like themselves.

6.5.3 Know that some cells are structured for specialised functions. 7.7.1 … know that cells are the basic building blocks of organisms and form tissues and organs.

6.5.4

Know that collections of cells with the same function form tissues (such as muscle) and that organs (such as the stomach) are made of tissues of different types.

7.7.2 … relate the overall structure of some specialised cells (e.g. nerve cells, sperm cells, xylem cells, palisade cells) to their functions.

6.5.5 Know that cells grow in size and increase in number by dividing in two.

6.2.3 Draw carefully labelled diagrams that show relationships, processes and observations

3 hours

Living things are made of cells

2 hours

Specialised cells, tissues and organs

1 hour

Cell division

6.3.3 Select and use specialised equipment correctly, safely and without damage to carry out experiments.

6.3.4 Use a simple microscope.

Unit 6L.1


Activities

Objectives Possible teaching activities Notes School resources

Magnification Introduce the concept of magnification. Help students use magnifying glasses and binocular microscopes correctly to look at small everyday objects, such as newsprint, coins, cloth. Show students magnified images and ask ‘Can you guess what they are?’ Discuss how many times each image has been magnified by comparing the actual and magnified sizes.

Show students how to carry and set up a microscope safely. Make simple slides of salt, sugar, sand and hair and demonstrate how to use and focus a microscope correctly at high and low power. Discuss why slides must be very thin.

Use a microscope that can project an image onto a screen to show students how to make clear drawings of what they see.

Provide prepared slides of insects, feathers, etc., so that students can practise focusing and drawing what they see and writing down the level of magnification.

You will need compound microscopes with a range of objective lenses x10, x20 and x40.

Also a microscope that can be projected onto a screen would be very useful.

Mathematics: Calculate total magnification when using a compound microscope from eye piece and objective lens e.g. x10 and x10 = x100 magnification.

Enquiry skills 6.2.3, 6.3.3, 6.3.4.

Use this column to note your own school’s resources, e.g. textbooks, worksheets.

3 hours

Living things are made of cells Know that living things are made up of cells.

Know that cells have cytoplasm, a nucleus and a cell membrane and that plant cells have a cell wall.

Draw carefully labelled diagrams that show relationships, processes and observations

Select and use specialised equipment correctly, safely and without damage to carry out experiments.

Use a simple microscope.

Cell structure Explore where the term ‘cell’ originates. Show students early microscope drawings by Robert Hooke and other scientists. Discuss how the microscope changed scientists’ view of living things. Ask ‘What is made of cells?’ and classify samples of rock, wax, wood, leather, fruit, etc., to conclude that only living objects, or objects that once lived, are made of cells. Demonstrate how to make a slide of onion epidermis cells and examine it under low and high magnification. Use a microscope that can project an image onto a screen to point out what air bubbles look like and explain how students can draw what they see. Name the parts of the cell that are visible: cell wall, cytoplasm and nucleus (possibly cell membrane). Now safely make or look at prepared slides of cheek cells and compare the structure of animal cells with that of plant cells. Discuss why plants have a cell wall (to help students remember this difference between animal and plant cells).

Use iodine solution to stain onion epidermis slides.

Enquiry skills 6.2.3, 6.3.3, 6.3.4

Safety: Carry out a risk assessment of making cheek cell slides – use cotton buds and dispose of them in disinfectant.

Unit 6L.1



Classifying cells Ask students to classify images of a variety of specialised cells (e.g. muscle cells, sperm, egg, phloem cells, palisade cells and root hair cells) as plant or animal cells. Ask students to justify their choice and label the parts of cells they recognise. Give students information about the function of each type of specialised cell to match to each image.

2 hours

Specialised cells, tissues and organs Know that some cells are structured for specialised functions.

Know that collections of cells with the same function form tissues (such as muscle) and that organs (such as the stomach) are made of tissues of different types.

Tissues and organs Return to an image of onion epidermis cells to explain that a collection of cells of the same type form a tissue. Compare this to the bricks that make a wall. Continuing the analogy, relate an organ (e.g. an onion bulb) made of different tissues to a room made of different materials. Include other plant organs – roots, leaves and flowers – to make an organism as different rooms make up a house.

Demonstrate layers of different tissues with a dissection (e.g. of a hen’s leg). Look at a transverse section of a leaf under a microscope to show that it is an organ made of different tissues. Ask students to draw a flowchart of cell, tissue, organ, organism for further examples.

Safety: Carry out a risk assessment of a dissection – swab the bench with disinfectant before and after.

1 hour

Cell division Know that cells grow in size and increase in number by dividing in two.

Ask students for their initial thoughts on the questions: ‘What happens when you grow?’, ‘Do cells get bigger or are there more cells?’, ‘Where do new cells come from?’. Show a sequence of photographs or film of an egg cell dividing and ask them to improve their answers.

Look at dividing plant material under the microscope (e.g. filamentous green algae, budding yeast, onion roots). Ask students to suggest which cells are making new cells, and which cells may have recently divided, giving reasons.

Provide diagrams that show the sequence of cell division and ask students to label and write a description of each stage.


Assessment

Examples of assessment tasks and questions Notes School resources

Label diagrams of plant and animal cells supplied. Provide diagrams for labelling and identification.

Identify common specialised cells from diagrams supplied and describe their function.

Sort these lists into the correct sequence of cells, tissue, organ, organism:

• Heart, muscle, human, muscle

• Shark, nerve, eye, retina

• Stem, plant, phloem, sieve tube

Assessment Set up activities that allow students to demonstrate what they have learned in this unit. The activities can be provided informally or formally during and at the end of the unit, or for homework. They can be selected from the teaching activities or can be new experiences. Choose tasks and questions from the examples to incorporate in the activities.

This is a Desert Rose, found on the sand flats (Sabkha) of Qatar.

Describe how you would find out whether a Desert Rose is made of cells.

Provide a picture of a desert rose. See, for example, www.spiritsandsouls.she-gogs.com/ Crystals.htm.

Unit 6L.1



Harmful micro-organisms

About this unit This unit is the second of five units on life science for Grade 6.

The unit is designed to guide your planning and teaching of lessons on life science. It provides a link between the standards for science and your lesson plans




Previous learning To meet the expectations of this unit, students should already know that individual micro-organisms are too small to see with the unaided eye. They should already know that some micro-organisms can cause illness.

Expectations By the end of the unit, students understand how to protect food from contamination by micro-organisms and that good hygiene will help protect them from microbial illness.

Students who progress further understand the importance of micro-organisms in nitrogen fixation, decomposition and nutrient recycling.

Resources The main resources needed for this unit are: • secondary sources – reference books or Internet access – to find out

about typhoid, cholera and other diseases caused by micro-organisms and which ones are prevalent in Qatar

• prepared slides or microscopic images of mould • video clip of time-lapse photography or images to show food going

mouldy • Glo Germ™ powder (www.glogerm.com) or glitter, ultraviolet lamp • bread, sealed clear plastic containers, small amounts of salt, sugar and

vinegar • Petri dishes with nutrient agar, prepared in aseptic conditions

Key vocabulary and technical terms Students should understand, use and spell correctly: • contamination, transmission, infection, epidemic, pandemic • tuberculosis, influenza, hepatitis, tetanus, diphtheria, typhoid, diarrhoea

UNIT 6L.2 6 hours



6 hours SUPPORTING STANDARDS CORE STANDARDS


6.10.1 Know that if left unprotected, most foods will be contaminated by micro-organisms in the air and become unfit to eat.

7.10.2 Know that micro-organisms in soil decompose organic matter and dead organisms and help to recycle nutrients.

4.10.2 Know that good hygiene is important in protection from illness caused by micro-organisms.

6.10.2 Understand that some micro-organisms can cause human illness and that regular washing and good food hygiene can reduce the risk of such illness.

4.10.1 Know that some micro-organisms can cause illness.

6.10.3 Find out about common human diseases caused by micro-organisms.

2 hours

Food spoiling

2 hours

Transmission of disease

2 hours

Infectious diseases

6.1.3 Turn questions into forms that can be investigated and plan the investigation.

Unit 6L.2


Activities


Remind students that micro-organisms are living things so small that you need a microscope to see them in detail.

Show students some examples of mouldy food in sealed containers (e.g. tomato, bread, cheese). Ask what has caused the decay and explain that mould is a fungus and a type of micro-organism. Ask students where the mould has come from and how could we prove this. Briefly describe Louis Pasteur’s swan-neck flask experiment of 1860 and how this proved food is contaminated by micro-organisms in the air. (Pasteur’s flasks, kept in France, are still sterile to this day!)

Allow students to study prepared slides or microscopic images of mould to see the structure of this fungus and the spores that spread the mould. Also show them a time-lapse video clip or images of food going mouldy and describe the changes that take place.

Enquiry skill 6.1.2


2 hours

Food spoiling Know that if left unprotected, most foods will be contaminated by micro-organisms in the air and become unfit to eat.

Turn questions into forms that can be investigated and plan the investigation.

Ask students to investigate what affects how fast bread goes mouldy. Get them to place sealed containers of bread in different locations around the school (e.g. fridge, freezer, in a room at normal temperature) and see how mouldy the bread is in two weeks’ time. Alternatively, get them to sprinkle a small amount of a different preservative (e.g. salt, sugar, vinegar) onto the bread in each container before sealing it, then keep all the samples in the same place and see how mouldy the bread is in two weeks’ time. Encourage students to generate their own investigative question, prediction and plan for how they will carry out this investigation.

Discuss the effects of eating mouldy food and ask students to suggest how they prevent food becoming mouldy at home.

Enquiry skill 6.1.3

Ask students about the effects of food poisoning. For example: • Why do you have sickness and diarrohea when you have food poisoning? (Answer: To get

rid of micro-organisms that have infected you, usually bacteria.) • Where have these micro-organisms come from? (Answer: Two sources – either they were

already in the food and it has not been cooked properly or the food has been contaminated, e.g. by the person preparing it.)

Ask students to write a set of hygiene rules for preparing food (e.g. keeping raw and cooked food separate), giving a reason for each one.

2 hours

Transmission of disease Understand that some micro-organisms can cause human illness and that regular washing and good food hygiene can reduce the risk of such illness.

Demonstrate why it is important to wash hands thoroughly by using glitter or Glo Germ™ (which shows up in ultraviolet light) to represent bacteria. Tell students to put some Glo germ™ or glitter on their hands and ask them to wash their hands. Then see if they have removed it all. Alternatively, get one student to put Glo Germ™ or glitter on their hands and ask them to open the classroom door. At the end of the lesson, examine everyone’s hands to see how many other students have been ‘infected’.

Ask students about other illnesses transmitted through food and drink. Use the Internet or reference books and leaflets to find out the incidence of cholera and typhoid in Qatar and the advice given to travellers to Qatar. Introduce the term epidemic and discuss how an outbreak of typhoid could start.

See www.glogerm.com for details of Glo Germ™.

Safety: Tell students not to look directly at the ultraviolet lamp. ICT opportunity: Use of the Internet.

Unit 6L.2



Ask students to find out where there are micro-organisms in the classroom. Give them sterile cotton wool buds and tell them to swab window sills and benches, and then to wipe the cotton wool buds over Petri dishes containing nutrient agar and then put lids on them. Incubate these dishes at room temperature for two weeks to see colonies of micro-organisms grow. Make sure students tape down the lids of the Petri dishes with a cross of tape and never reopen the dish after incubation. Discuss why students should lift the lid of their Petri dish at an angle and expose the agar for the minimum length of time when collecting their samples.

Safety: Tell students not to collect samples from the floor as these may contain soil and potential pathogens.

Review the different types of micro-organisms; bacteria, virus, fungi and protozoa. Ask students to find out from textbooks or the Internet about common human infectious diseases and which type of micro-organism causes them.

Ask students to make a fact file for each disease that includes the micro-organism, method of transmission, symptoms (including risk to life), treatment and whether the disease is prevalent in Qatar.

Introduce the term pandemic to describe diseases such as AIDS, tuberculosis and influenza that have global impact.

Challenge students to find out about the difference between the common cold and influenza. Ask them to organise their research into a table so they can compare and contrast: micro-organism, transmission, site of infection, first symptoms, main symptoms and treatment.

ICT opportunity: Use of the Internet

2 hours

Infectious diseases Find out about common human diseases caused by micro-organisms.

Extension activity Ask students to research a disease that is of worlwide concern; ask them how likely it is that the disease becomes a pandemic and how this could be prevented? Encourage students to write a fictional news article describing a pandemic outbreak, including where it started and how it was brought under control.


Assessment


Use your knowledge of micro-organisms to explain why:

a. frozen food that is not thoroughly reheated can give you food poisoning;

b. you should cover your nose with a tissue when you sneeze;

c. you should wash your hands after using the toilet;

d. a nurse wears rubber gloves to clean and bandage a cut.


Spots may be caused by bacteria in the skin. A researcher investigated the effect of spot-lotion on bacteria. He grew bacteria on the surface of agar jelly in a Petri dish.

The researcher placed two small paper discs onto the surface of the jelly. One disc had been soaked in spot-lotion. The other disc had been soaked in water.

The diagrams below show the jelly at the beginning of the experiment and two days later.

a. Suggest what had happened to the bacteria in the clear area around the paper disc soaked in spot-lotion.

b. What was the control in this experiment?

c. Give two safety precautions the researcher should take to avoid contact with the bacteria.

Adapted from QCA Year 9 science test, 2001

Unit 6L.2



Classification

About this unit This unit is the third of five units on life science for Grade 6.





Previous learning To meet the expectations of this unit, students should already know the main characteristics of the vertebrate groups (fish, amphibian, reptile, bird and mammal) and know how vertebrates differ from invertebrates.

Expectations By the end of the unit, students classify animals and plants into their major groups.

Students who progress further distinguish between environmental and inherited variation.

Resources The main resources needed for this unit are: • images of a variety of different vertebrates mounted skeletons of a variety of vertebrates or diagrams of animals

showing the skeleton video clips, images or preserved specimens of a variety of invertebrates a variety of different flowering plants bean and wheat seeds soaked for an hour or overnight, scalpel and hand

lens images or fresh or preserved specimens of a variety of different non-

flowering plants

Key vocabulary and technical terms Students should understand, use and spell correctly: • classify, characteristics, taxonomic group • vertebrates, amphibians, invertebrates, arthropods, cnidaria, coelentera,

crustacean, echinoderm • monocotyledon, dicotyledon, algae, liverwort, conifer, fungi

UNIT 6L.3 6 hours





5.4.1 Recognise the main distinguishing features of the vertebrate groups (fish, amphibian, reptile, bird, mammal) and know how vertebrates differ from invertebrates.

6.4.1 Place an animal into its major vertebrate (fish, amphibian, reptile, bird, mammal) or invertebrate (single cell, coelenterate, arthropod (e.g. crustacean and insect), echinoderm, flatworm, mollusc, round worm, segmented worm) taxonomic group.

7.5.1 Know that some features of organisms are inherited while others are determined by their environment.

3 hours

Classifying animals

3 hours

Classifying plants

6.4.2 Place a plant into its major flowering (dicotyledon, monocotyledon) or non-flowering (algae, conifer, fern, fungi, liverwort, moss) taxonomic group.

Unit 6L.3


Activities


Provide students with pictures of a range of vertebrates and ask them to classify them into groups.

Discuss students’ reasons for putting different animals into groups. Pick out bat, dolphin and penguin. Discuss which is the best way to group these – can fly and live in water or birds and mammals. Ask which is more scientific.

Show students skeletons or drawings of skeletons of different animals and define the groups vertebrates and invertebrates. Make sure students correctly group snakes, lizards and frogs as vertebrates. Ask them to complete a table looking at the characteristics of different vertebrate groups (e.g. can or can’t control body temperature, have damp skin, scales, hair or fur, lay eggs, feed young with milk).

Show students video clips, images or preserved specimens of invertebrates. Encourage them to apply what they have learnt about classifying scientifically to grouping invertebrates (e.g. invertebrates with an exoskeleton, muscular foot or segments).

Define the main invertebrate groups: single cell, coelenterate, arthropod, echinoderm, mollusc, round, flat and segmented worms. Use the meaning of the roots of these words to help students understand them – e.g. coelenterate (hollow), mollusc (soft), arthro (jointed) pod (leg).

Summarise the classification of animals in a branching diagram. Explain the different taxonomic groups – e.g. kingdom (animals), phylum (vertebrates) and class (mammals).

Present students with an image of an unfamiliar animal (e.g. armadillo, sea cucumber) and ask them to speculate on which animal group it belongs to.


3 hours

Classifying animals Place an animal into its major vertebrate (fish, amphibian, reptile, bird, mammal) or invertebrate (single cell, coelenterate, arthropod (e.g. crustacean and insect), echinoderm, flatworm, mollusc, round worm, segmented worm) taxonomic group.

Extension activity Research an unusual animal and present a brief report about the animal’s characteristics and the group it belongs to.

Unit 6L.3



Ask students to list the characteristics of plants (stem, leaves, flowers and roots). Ask them whether all plants have these features. Explain that these are the features of flowering plants.

Provide students with a range of flowering plants, or parts of flowering plants, to make observational drawings of. Explain that all these plants have flowers – some are big and colourful, and others are very small. Ask students to explain why there are these differences in the size of flowers – what does it have to do with how the plant is pollinated?

Remind students of the way animals are classified into groups and explain that flowering plants are divided into two groups depending on the number of seed leaves or cotyledons. Describe the difference between dicotyledon and monocotyledon flowering plants, namely that monocotyledon leaves have parallel veins whereas dicotyledon leaves have branching veins. Ask students to identify one of each type of flowering plant from the range you have provided. Provide students with a monocotyledon seed (e.g. wheat) and dicotyledon seed (e.g. bean) to dissect to show how the number of seed leaves is different.

Define the main non-flowering groups: algae, conifer, fern, fungi, liverwort and moss. Show students specimens or photographs of each group. Ask students to complete a table looking at the characteristics of non-flowering plants (e.g. has stem, leaves, roots, makes spores or makes seeds, green).

Summarise the classification of plants in a branching diagram. Remind students of the different taxonomic groups – e.g. kingdom (plants), phylum (flowering plants), class (monocotyledon).

Suitable plants, or parts of plants, include cut flowers, house plants, cactus, succulents, grasses, a small branch of a tree.

Soak the bean and wheat seeds for an hour or overnight and supply students with a scalpel and hand lens.

Safety: Make sure that students take care when using a scalpel.

3 hours

Classifying plants Place a plant into its major flowering (dicotyledon, monocotyledon) or non-flowering (algae, conifer, fern, fungi, liverwort, moss) taxonomic group.

Review Review the whole classification unit by playing ‘Who am I?’. Read out a description of a plant or animal and challenge students to identify the group (e.g. ‘I lay eggs, I am warm blooded and I have feathers; who am I?’; ‘I grow very tall, my leaves are the shape of needles and I produce seeds in cones; who am I?’).

Get students to write their own “Who am I?” clues for other students to guess.


Assessment


The five vertebrate groups are fish, mammals, amphibians, reptiles, birds.

a. Which two groups lay eggs in water?

b. Which two groups can control their body temperature?

c. Which two groups are covered in scales?

Here are four different plant groups: flowering plants, algae, conifer and fern. Choose one plant group to answer each question.

a. Which group of plants produces seeds in cones?

b. Which group produces spores under its leaves?

c. Which group does not have roots?

d. Which group does a mangrove tree belong to?

Leeches have a segmented body. They live in fresh water and feed on blood. They can squeeze through very small gaps in clothing to reach skin and bite their host.

Use this information to answer the questions below.

a. What piece of information shows that leeches are invertebrates?

b. What invertebrate group do you think leeches belong to? A leech


Here is a graph of the body temperature of a lizard and a mouse as the room temperature increases.

a. Which line represents the lizard, line A or B? Give a reason for your answer.

b. A mouse has to eat more than 4 times the amount that a lizard does. Use the information in the graph to suggest a reason why.

Unit 6L.3



Teeth and eating

About this unit This unit is the fourth of five units on life science for Grade 6.




Introduce the unit to students by summarising what they will learn and how this builds on earlier work. Review the unit at the end, drawing out the main learning points, links to other work and ‘real life’ applications.

Previous learning To meet the expectations of this unit, students should already know that the human body requires food and that food provides energy. They should know that the intestines absorb food and that the heart pumps blood around the body to carry gases, food and waste. They should be able to plan and conduct systematic controlled investigations. They should be able to identify patterns in observations and draw generalised conclusions from them, and make simple calculations from experimental data.

Expectations By the end of the unit, students describe the overall anatomy of the human digestive system. They know the structure of a human tooth and can explain the functions of different teeth. They know how to care for their teeth. They conduct systematic investigations, make predictions from and identify patterns in data and observations, and consider whether evidence supports a conclusion, prediction or hypothesis.

Students who progress further know the structure of the digestive system and understand the functioning of enzymes. They distinguish between digestion and absorption of food. They understand the need for accuracy and know how to achieve it.

Resources The main resources needed for this unit are: • models and diagrams of a set of teeth and cut-away of a single tooth • disclosing tablets • video clip, animation or sequence of diagrams of tooth decay • hard-boiled egg shells • calcium carbonate, sodium bicarbonate, white tiles, marker pens,

toothbrushes • diagrams or skulls of cat or dog and rabbit or sheep • outline diagrams of human body and human digestive system, model

human torso (optional) • 9 m length of tubing

Key vocabulary and technical terms Students should understand, use and spell correctly: • molars, canines, incisors, enamel, dentine, pulp, oral hygiene, plaque • digestive tract, salivary glands, oesophagus, stomach, liver, gall bladder,

pancreas, large intestine, small intestine, rectum, anus

UNIT 6L.4 8 hours





6.8.1 Identify and describe the general structure of the human digestive system and know how the mouth, salivary glands, oesophagus, stomach, liver, gall bladder, pancreas, large and small intestine, and anus are connected.

8.6.1 Recall the general structure of the human digestive system and explain the functions of the digestive organs (mouth, oesophagus, small and large intestines and colon, stomach, liver, gall bladder and pancreas).

6.8.2 Know that blood carries dissolved food to cells of the body. 8.6.2 Explain digestion as the breakdown of large insoluble food molecules into smaller soluble molecules that can be absorbed into the blood stream for transport round the body.

5.7.1 Know that humans require food as an energy source.

6.9.1 Know that humans grow two sets of teeth.

6.9.2 Describe the structure of a tooth as consisting of enamel, dentine and pulp, and know that teeth are connected to the blood and nervous systems.

6.9.3 Know the names and normal numbers of the types of human teeth (molars, premolars, canines and incisors) and explain how they are adapted for their functions.

6.9.4 Know the causes of tooth decay and how the risk of this can be avoided by good oral hygiene.

6.9.5 Compare the dentition of humans with that of other animals and explain the differences in terms of diet.

6.1.1 Plan investigations, controlling variables and collecting an appropriate range of evidence, identify patterns in observations and data, draw appropriate generalised conclusions and test predictions.

5.1.1 Plan investigations with an understanding of the importance of controlling variables and of collecting an appropriate range of evidence, observations and relevant data in a systematic manner.

6.1.2 Consider the extent to which evidence justifies a conclusion or supports a prediction or hypothesis.

4 hours

Types of teeth; preventing tooth decay

1 hour

Dentition of other animals

3 hours

Digestive system

5.1.2 Identify patterns in observations and data, draw appropriate, generalised conclusions and use the data to test predictions.


7.1.4 Understand the importance of accuracy and use techniques such as repetition ofmeasurements to ensure it.

Unit 6L.4


Activities


Ask students to discuss in small groups what they already know about teeth and produce a spider diagram of this information. Take feedback from the groups and summarise that humans have two sets of teeth: milk teeth and adult teeth. Also conclude that teeth are used to cut and chew food into small enough pieces to swallow and digest.

Show students a model of adult teeth and give them small mirrors to use to look at their own teeth. Provide a diagram of adult teeth and ask students to label molars, canines and incisors and annotate with the purpose of each type of tooth. Also ask them to mark on the diagram any fillings they have or missing teeth and relate this to the dental record a dentist keeps.

Safety: Make sure small mirrors do not have sharp edges. Cover the backs with stick tape so pieces do not scatter if broken.

Enquiry skill 6.2.1


Explain to students the internal structure of a tooth using a cut-away diagram or model. Provide a diagram of a tooth and ask students to label enamel, dentine and pulp. Ask them why teeth are connected to the blood and nervous systems.

Ask students to write a list of instructions for good dental care and how to prevent tooth decay and gum disease, including when the best time to clean teeth is. Ask students to bring their toothbrush in and use disclosing tablets to show how well their brushing technique removes plaque.

Show students a video clip, animation or sequence of diagrams of tooth decay and describe the action of bacteria on teeth and gums. Ask students at what point they think tooth decay will cause toothache.

Return to milk teeth and ask students why we have two sets of teeth. Discuss the difference in consequences of losing a milk tooth and losing an adult tooth.

4 hours

Types of teeth; preventing tooth decay Know that humans grow two sets of teeth.

Know the names and normal numbers of the types of human teeth (molars, premolars, canines and incisors) and explain how they are adapted for their functions.

Describe the structure of a tooth as consisting of enamel, dentine and pulp, and know that teeth are connected to the blood and nervous systems.

Know the causes of tooth decay and how the risk of this can be avoided by good oral hygiene. Plan investigations, controlling variables and collecting an appropriate range of evidence, identify patterns in observations and data, draw appropriate generalised conclusions and test predictions. Consider the extent to which evidence justifies a conclusion or supports a prediction or hypothesis. Turn questions into forms that can be investigated and plan the investigation.

Encourage students to investigate a number of questions about dental health (e.g. how do sugary drinks affect teeth?). Suggest that students use hard-boiled egg shells to represent teeth and let them place the egg shells in a range of different sugary drinks, sugar free drinks, fruit juice and water. Tell them to observe how the drinks have affected the egg shells after a week. Alternatively, get them to investigate which toothpaste is most effective at preventing tooth decay by coating pieces of eggshell with a variety of toothpastes, placing them in a sugary drink and observing the egg shell after one week.

Show students how to make their own toothpaste by mixing calcium carbonate and sodium bicarbonate with a little water. Ask them to compare commercial toothpastes or the toothpaste they have made by making a mark with a permanent marker on a white tile and seeing how easy it is to clean off using different toothpastes. Students will need to take care to make the test fair by counting the number of times they clean with the toothbrush or how much the mark has disappeared after 30 seconds of constant brushing.

Enquiry skills 6.1.1–6.1.3

Unit 6L.4



1 hour

Dentition of other animals Compare the dentition of humans with that of other animals and explain the differences in terms of diet.

Provide students with pictures of several different animals with different diets (e.g. cat, rabbit, shark, sparrow, sheep) and pictures of what they eat (mice/small birds, lettuce/seeds, seals/fish, seeds/insects, grass). Ask students to link the animals to their diet. Ask students which animals are herbivores, omnivores and carnivores. Also ask if all these animals have teeth.

Show students diagrams or skulls of a dog or a cat and a rabbit or a sheep. Ask students whether they can work out which skull is which and give reasons for their answers by referring to the different types of teeth the animals have.

Ask students to compare the arrangement of teeth in these animals to human teeth and to explain what human teeth tell us about the human diet.

Elicit students’ prior knowledge about the digestive system by providing an outline of a human body and asking them to draw and label on the diagram what happens to food once it has been eaten. Also ask them to write their own definition of digestion.

Discuss their ideas (and misconceptions) and show them a 9 m length of tubing to represent how long the average adult human digestive tract is. Explain to students that food enters the top of this tube through the mouth, travels all the way down and undigested food leaves the other end of the tube through the anus. Tell them that digestion is the breakdown of food as it passes down this tube so that dissolved food can be absorbed into the blood.

Explain to students that digestion actually begins in the mouth when food is mixed with saliva produced by the salivary glands. As a homework activity, ask students to chew a small piece of bread for several minutes and to pay attention to how the taste changes: they will notice it begins to taste sweet as the starch in the bread is broken down into sugar.

Students do not need to know about the function of digestive enzymes in this unit; they will learn about the action of specific enzymes in Grade 8.

Provide students with a diagram of the human digestive system and ask them to label it. If possible, also show them the digestive system on a model of a human torso. Encourage students to identify each part of the digestive tract (oesophagus, stomach, small intestine, large intestine, rectum) and the organs associated with digestion (salivary glands, liver, gall bladder, pancreas). Ask students to use textbooks to find out what happens to food in each part of the digestive tract and the role of each of the associated organs, and to make their own notes.

3 hours

Digestive system Identify and describe the general structure of the human digestive system and know how the mouth, salivary glands, oesophagus, stomach, liver, gall bladder, pancreas, large and small intestine, and anus are connected.

Know that blood carries dissolved food to cells of the body.

Clarify that two main processes occur in the digestive system – digestion and absorption. Ask students where absorption of dissolved food takes place and where this dissolved food goes next. Remind them that food provides the body with energy and that blood carries food to every cell of the body.

Provide students with information on the actual length of each part of the digestive tract and ask them to make a scale drawing of the digestive tract straightened out and label how much of this is the oesophagus, stomach, small intestine, large intestine and rectum. Ask students why the digestive tract is so long and what would happen if it was only half this length.

Finally, ask students what they think most undigested food is made of and discuss the importance of fibre in our diet to help keep the digestion system moving.

Mathematics: Producing a scale drawing.

Review Ask students to write a story of the journey of a piece of bread through the digestive system. Make sure they include each part of the digestive tract and all the associated organs in their story.


Assessment


Explain the following:

a. Children are told to chew their food properly before swallowing it.

b. If you don’t eat enough fibre in your diet you can become constipated.

c. You should clean your teeth after, rather than before a meal.

d. Carnivores have large canine teeth.

e. Many herbivores do not have canine teeth.


Teeth a. Most human babies are born without teeth. Why do babies not need teeth?

b. What do teeth do? Choose two of the following:

grind up food;

break down food chemically;

help to taste food;

tear off lumps of food;

grow fillings.

c. Use the information in the chart below to answer these questions:

i. Which place has the least tooth decay?

ii. What evidence is there in the chart that eating sugar causes tooth decay?

60 50 40 30 20 10 2 4 6 8 10 12

This side of the chart shows the mean(average) amount of sugar eaten inone year by a person in each place.

This side of the chart shows the mean(average) number of decayed teethfor a person in each place.

Mean (average) amount of sugar eaten, in kg Mean (average) number of decayed teeth


Unit 6L.4



Organs and systems

About this unit This unit is the fifth of five units on life science for Grade 6.





Previous learning To meet the expectations of this unit, students should be able to name the life processes common to all living things. They should already know that humans and other animals have lungs for gas exchange, intestines for absorbing food, kidneys for dealing with waste and a heart for circulating blood around the body. They should be able to describe the main stages in the reproduction of flowering plants. They should know that sexual reproduction in animals requires mating.

Expectations By the end of the unit, students list the main organs of animals and parts of plants and their functions. They differentiate between internal and external fertilisation. They understand the changes that occur during puberty. They can use a simple microscope.

Students who progress further know the basic anatomy of the human reproductive system. They know about human reproduction and about the growth, development and birth of a baby.

Resources The main resources needed for this unit are: • model torso • 10 cards with pictures of 10 different organs: brain, lungs, heart, salivary

glands, stomach, liver, pancreas, small intestine, kidneys, ovaries. • animal behaviour video showing examples of animal reproduction • celery, dye, scalpel, microscope with low and high power objective lenses • nail varnish, lettuce, privet and holly leaves • Internet access

Key vocabulary and technical terms Students should understand, use and spell correctly: • skeletal and muscular system, respiratory and circulatory system, nervous

system, reproductive system, excretory system and digestive system. • thyroid, salivary glands, oesophagus, stomach, liver, gall bladder,

pancreas, spleen, bladder, uterus, ovaries • internal fertilisation, external fertilisation, puberty • xylem, phloem, stomata

UNIT 6L.5 8 hours





3.6.2 Know that humans and other animals have lungs for gas exchange, intestines for absorbing food, kidneys for dealing with waste and a heart for circulating blood.

5.6.1 Know that living organisms require air, food and water, and that they release waste; know that they are sensitive and that they grow and reproduce to create more organisms like themselves.

6.6.1 Know the names of the main organs of vertebrates that are responsible for circulation (heart, blood vessels), food processing (stomach, liver and intestines), gas exchange (lungs, gills), locomotion (fins, legs, wings) reproduction (ovaries, testes), sensitivity (brain, nerves, sense organs) and waste removal (kidneys).

7.8.1 Know the simple anatomy of the human female and male reproductive systems; know the basic facts about human reproduction and about the growth, development and birth of a baby.

5.6.3 Know that sexual reproduction in fish, amphibians, reptiles, birds, mammals and insects requires adult males and females to mate.

6.6.2 Differentiate between internal and external fertilisation; know that animals that have internal fertilisation have organs specialised for this purpose.

4.8.1 Describe the main stages in the reproduction of flowering plants.

6.6.3 Know the parts of flowering plants that are responsible for anchorage (roots), circulation (xylem and phloem), gas exchange (stomata), food production (leaves and stems), reproduction (flowers) and waste removal (stomata).

6.6.4 Be able to locate, identify and compare the relative size of the main internal organs of humans (brain, lungs and windpipe, heart, thyroid, salivary glands, oesophagus, stomach, liver, gall bladder, pancreas, spleen, large and small intestine, kidneys, bladder, uterus, ovaries).

6.7.1 Understand that during puberty the body changes to enable reproduction and that this also results in the development of secondary sexual characteristics.

3 hours

Major human systems; function of human organs

1 hour

Internal and external fertilisation

1 hour

Puberty and reproductive organs

3 hours

Organs of plants; structure of a flower

6.3.4 Use a simple microscope.

Unit 6L.5


Activities


Ask students whether they can remember seven life processes from Unit 5.1 (movement, respiration, sensitivity, growth, reproduction, excretion, nutrition). Remind students how the human body is organised: cells, tissues, organs and systems. Ask students to match a system to each life process (except growth) from the choice: • skeletal and muscular system; • respiratory and circulatory system; • nervous system; • reproductive system; • excretory and digestive system.

Use a model torso to help students recognise the major organs of the body.

Divide the class into seven groups and ask each group to put together a display about one particular system. Ask students to include what the function of this system is, what organs are involved and where they are found in the body. Students will need reference books to find this information. Ask each group to present the display of their allocated system to the rest of the class.


To make sure that students have a good understanding of all the systems found in a human body, challenge them to apply what they know to a different vertebrate group – fish. Fish are adapted to life in water with gills and fins – ask students which systems these organs belong to.

Help students to appreciate the relative size of different organs by providing them with a set of 10 cards with pictures of 10 different organs: brain, lungs, heart, salivary glands, stomach, liver, pancreas, small intestine, kidneys and ovaries. Challenge students to first name the organs, then put them into order from smallest to largest organ and finally to label a diagram of the human body to show the position of each one.

Now provide students with a diagram that shows some organs they may not have come across before (e.g. spleen, gall bladder, thyroid gland). Describe the symptoms of an overactive thyroid gland (weight loss, anxiety, a racing heart beat, feeling too hot) and an underactive thyroid (fatigue, weakness, weight gain, depression, feeling too cold). From this information students can deduce what the thyroid might do. Symptoms of gall stones in the gall bladder include severe abdominal pain shortly after eating – especially chocolate, cheese and fatty foods. Ask students what they think the gall bladder’s function is.

Prepare sets of cards showing the organs of the body.

3 hours

Major human systems; function of human organs Know the names of the main organs of vertebrates that are responsible for circulation (heart, blood vessels), food processing (stomach, liver and intestines), gas exchange (lungs, gills), locomotion (fins, legs, wings) reproduction (ovaries, testes), sensitivity (brain, nerves, sense organs) and waste removal (kidneys).

Be able to locate, identify and compare the relative size of the main internal organs of humans (brain, lungs and windpipe, heart, thyroid, salivary glands, oesophagus, stomach, liver, gall bladder, pancreas, spleen, large and small intestine, kidneys, bladder, uterus, ovaries).

Extension activity Challenge students to find out which of the body organs they have been learning about we can live without and which are essential for life. Explain that patients sometimes have an organ surgically removed, because of damage, infection or a tumour. Ask students how difficult it would be to live without a spleen, thyroid, stomach, gall bladder, pancreas, large intestine, kidneys or liver. They will need access to the Internet and reference books to research their answers.


Unit 6L.5



1 hour

Internal and external fertilisation Differentiate between internal and external fertilisation; know that animals that have internal fertilisation have organs specialised for this purpose.

Remind students that all living things reproduce and that many animals have two different sexes: male and female. Also remind them that females have ovaries to produce eggs and males have testes to produce sperm. (Some animals – e.g. earthworms – are both sexes and have ovaries and testes.) Explain that when sperm from a male meet the egg from a female the nuclei of the two cells fuse and this is called fertilisation.

Explain to students that when egg and sperm meet outside the female’s body this is external fertilisation and when they meet inside the female’s body this is internal fertilisation. Watch a video that shows how different animals reproduce or provide students with written information about reproduction in various animals (e.g. fish, frogs, birds, insects, mammals). Ask students to collate one list of animals that reproduce using external fertilisation and another list of animals that reproduce using internal fertilisation. Prompt students to notice that most animals that live in water, or return to water to breed, do so by external fertilisation. Ask students which animals are exceptions to this pattern and why (e.g. dolphins are mammals that live in water). Ask students to explain why all animals that live exclusively on land have internal fertilisation.

Explain to students that for internal fertilisation to occur, the male needs to place sperm inside the female’s body so it can swim to the egg or eggs. In mammals, the male has an organ called a penis for this purpose.

1 hour

Puberty and reproductive organs Understand that during puberty the body changes to enable reproduction and that this also results in the development of secondary sexual characteristics.

Remind students of work they have done on life cycles in Grade 5, when they defined adolescence as the time when humans reach reproductive maturity and explain that this is also called puberty. Explain to students that puberty can begin from the age of 10 onwards and involves a number of body changes as sexual organs take on their adult form. Provide students with a list of body changes that occur during puberty and ask them to sort them into changes that happen only to boys, only to girls and to both boys and girls. Discuss students’ answers and make it clear that these changes happen gradually over time and at different ages for different individuals.

To extend this subject further, encourage students to invent problem page questions and answers about what it is like to go through puberty (e.g. a 15-year-old boy worried that his voice is still high pitched).



Remind students that plants are also living things that carry out seven life processes and are organised into cells, tissues and organs. Ask students to draw a large diagram of a flowering plant, including the roots, and to label all the organs of a plant that they know. Next to each label, ask students to further annotate their diagram with the function of each organ. This will give you the opportunity to check for any misconceptions students have (e.g. that plants get food through their roots).

Students should have labelled on their diagrams that roots are for anchorage and flowers are the organs of reproduction. Check that students remember that reproduction in plants involves pollen and ova. Remind them that photosynthesis occurs in the leaves of plants for plants to make sugars. This means that, unlike animals, plants do not need a ‘digestive system’.

Introduce students to a plant’s circulation system and explain that plants have two different types of tubes running through them: xylem to transport water and phloem to transport dissolved sugars. Ask students to identify where dissolved sugars are transported from and to and where water is transported from and to. Give students celery stems that have been in a beaker of dyed water for a few hours. Ask them to carefully slice transverse sections of the celery and observe where the dye is, using a hand lens and microscope.

Explain to students that water evaporates from the leaves of plants through tiny holes in the leaves called stomata. These tiny holes also allow gas exchange to occur. Let students observe stomata by carefully tearing apart a lettuce leaf and placing a small piece of the underside layer of the leaf onto a slide to examine under a microscope. Alternatively, get them to paint the underside of a holly or privet leaf with a number of layers of nail varnish, peel the hardened varnish off and observe it using high magnification.

Explain to students that plants respire and carbon dioxide is a waste product that moves out of the plant through stomata. This means that stomata are also involved in waste removal.

Enquiry skill 3.4

Safety: Students must take care when using scalpels.

3 hours

Organs of plants; structure of a flower Know the parts of flowering plants that are responsible for anchorage (roots), circulation (xylem and phloem), gas exchange (stomata), food production (leaves and stems), reproduction (flowers) and waste removal (stomata).

Review Students often find it difficult to remember and explain the functions of different plant organs. To consolidate their learning you could ask them to make a 3D model of a flowering plant that shows through the choice of materials what each part does. For example, they could use straws to represent the xylem and phloem of the stem, a thin layer of green plastic and green sponge to represent leaves, and so on.


Assessment


Read each sentence below carefully. For each one, decide whether the sentence is describing internal fertilisation or external fertilisation.

A. This happens for most animals that live on land.

B. This happens for most animals that live in water.

C. The egg and sperm come together inside the female.

D. The egg and sperm come together outside the female.

E. Sperm swim through water to reach the eggs.

F. Many eggs are produced and many do not survive.

G. A few eggs are produced and more survive.

The diagram below shows an organ system in the human body.

a. What is the name of the organ system shown in the diagram?

b. What are the names of parts A and B?

c. Parts C are bones which support the chest. Give the name of these bones.



Plants have organs and organ systems that have different functions.

Complete the table:

Organ system Function in the plant

Xylem transports water and phloem transports dissolved sugars

Reproductive system

Carbon dioxide passes out of stomata in the leaves

Unit 6L.5

241 | Qatar science scheme of work | Grade 6 | Unit 6M.1 | Materials 1 © Education Institute 2005

GRADE 6: Materials 1

Solubility

About this unit This is the first of four units on materials in Grade 6. This unit builds on the study of the properties of water in Unit 5M.1. Unit 7M.1 interprets dissolving in terms of the particle model and many of the ideas introduced here are exploited in Units 6M.2 on mixtures and 7M.2 on purification methods.

The unit is designed to guide your planning and teaching of lessons on materials. It provides a link between the standards for science and your lesson plans.




Previous learning To meet the expectations of this unit, students should already know that water is a liquid and is a good solvent but that not everything dissolves in it. They should also be aware that water is not the only liquid in which substances can dissolve.

Expectations By the end of the unit, students recognise that the rate of dissolving is affected by various factors, that some solids are more soluble than others and that there are many useful solvents. They conduct systematic investigations, make predictions from and identify patterns in data and observations, and consider whether evidence supports a conclusion, prediction or hypothesis. They recognise patterns in results.

Students who progress further define solubility and understand the concept of a saturated solution. They recognise that these concepts apply to gases as well as solids. They intuitively recognise that different liquids, both miscible and immiscible, can form layers according to their density and that objects sink further in less dense liquids than in more dense ones. They recognise patterns in results and perform calculations with data.

Resources The main resources needed for this unit are: • an investigation planning poster that will help to identify and control

experimental variables • 100 cm measuring cylinder • tared balance accurate to 0.1 g • video clip of oil spillage

Key vocabulary and technical terms Students should understand, use and spell correctly: • liquid, solid, dissolve, solution, solute, solvent, soluble, insoluble • solubility, saturated solution • miscible, immiscible

UNIT 6M.1 7 hours





6.11.1 Recognise that the rate of dissolving is affected by several factors, such as heat, particle size and stirring.

5.9.6 Know that water is a good solvent but that not all substances dissolve in water.

6.11.2 Know that some solids are more soluble in a solvent than others and that there is always a limit to the amount of solute that will dissolve.

9.15.7 Explain the importance of maintaining the concentration of dissolved oxygen in water and describe some of the processes that reduce it.

6.11.3 Know that a solute can often be recovered by evaporating the solvent, which can then be recovered by condensing it.

5.9.7 Know that water is not the only liquid and solvent; other common ones are methylated spirit and petrol.

6.11.6 Know that there are many useful solvents (common ones are water, methylated spirit and petrol) and that these do not always mix with each other.

6.1.2 Consider the extent to which evidence justifies a conclusion or supports a prediction or hypothesis.


4 hours

Dissolving in water

3 hours

Different solvents dissolve different substances

6.3.2 Measure accurately, using the correct units, the mass and volume of solids and liquids.

Unit 6M.1


Activities


Recall Grade 5 work on solubility Remind students of the meaning of key words – solute, solvent, soluble, insoluble. Set a challenge to help them recall the work. Present them with various solutions and suspensions and challenge them to predict which liquid is pure and which contains something that is dissolved and then test their predictions. The liquids should range from water and sand, powder paints, food colouring in water, salt water, to distilled water and could include solutions in alcohol. Help students, where necessary, to turn the question into a systematic investigation. Ask them how well the results justified their predictions.

Enquiry skills 6.1.1, 6.1.3


How fast does a solute dissolve? Get students to think about everyday examples of dissolving (e.g. sugar in tea, salt in cooking) and to think further to predict what factors might affect how fast a substance dissolves in water. They will be able to suggest a number of possible variables, such as temperature, rate of stirring, volume of water, how fine the solid was. Encourage different groups to investigate the effects of different variables. Draw together the results from the different groups and summarise.

The investigation planning poster will help students work out which variables they will control and which they will measure.

Enquiry skill 6.1.1

4 hours

Dissolving in water Turn questions into forms that can be investigated and plan the investigation.

Recognise that the rate of dissolving is affected by several factors, such as heat, particle size and stirring.

Measure accurately, using the correct units, the mass and volume of solids and liquids.

Know that some solids are more soluble in a solvent than others and that there is always a limit to the amount of solute that will dissolve.

Know that a solute can often be recovered by evaporating the solvent, which can then be recovered by condensing it.

How much solute will dissolve? Select a salt that is readily soluble in water (sodium hydrogen carbonate is a good one) and ask students how they could investigate what factors might affect how much will dissolve. Ask them to think of the possible variables that might influence this and how they might investigate the effect of each variable. In this case, suggest each group use the same temperature but different volumes of water. This will give them practice in measuring out accurate volumes of water and masses of solute. They should use volumes of water ranging from 10 cm3 to 50 cm3 and add the sodium hydrogen carbonate in units of 0.5 g (solubility is about 8% w/v at room temperature) until no more dissolves. Introduce the term saturated solution and, for more advanced students, solubility.

Students should look for patterns in the data. They will see that the greater the volume, the more will dissolve. More advanced students can calculate the solubility in g/dm3. They can check by repeating results or comparing with others and taking average readings.

Ask more advanced students to compare different solutes and plot a bar graph showing the relative solubilities. Sodium carbonate and sodium chloride can be used.

Enquiry skills 6.1.1, 6.2.4, 6.3.2

The poster on planning investigations will help students work out which variables they will control and which they will measure.

Mathematics: A knowledge of ratio and proportion is needed (mathematics standards section 6.6).

Unit 6M.1


Objectives Possible teaching activities Notes School resources Air dissolves in water

Allow students to watch carefully what happens as you heat some tap water in a glass beaker. They will observe bubbles produced (mainly on the side of the vessel) before the onset of boiling. Ask them what they think the bubbles are. Some will say water vapour but others may suggest air or ‘a gas’. Challenge them to think about how to investigate this. The bubbles can be collected in an inverted plastic beaker that just fits inside the vessel. The use of boiling aids such as marbles will help produce bubbles in the middle and not around the outside where they are difficult to collect. Ask students if they can smell the gas collected? Ask them where they think the gas came from.

Both nitrogen and oxygen come from the air, but oxygen is more soluble than nitrogen, so the gas that is boiled out of the liquid may be as much as 50% oxygen. Relate this dissolved air to the survival of many organisms under water.

Miscible and immiscible liquids Ask groups to shake up or stir up a mixture of cooking oil and water and watch what happens. The two liquids will gradually separate into layers with the oil on top. Then ask the groups to add a drop of food colouring to the mixture and shake or stir again. As the liquids settle, the colour will be seen in the water layer. Ask for explanations of this observation.

Refer back to work done in Grade 5 showing that substances which dissolved well in water did not dissolve well in substances that did not mix with water, and vice versa. Check students’ understanding of this by asking them to predict how soluble they think a number of substances might be in cooking oil and water. Suggest substances such as fat, sugar, salt, petroleum jelly, candle wax.

3 hours

Different solvents dissolve different substances Know that there are many useful solvents (common ones are water, methylated spirit and petrol) and that these do not always mix with each other.

Consider the extent to which evidence justifies a conclusion or supports a prediction or hypothesis.

Cleaning up an oil spill Raise the issue of oil spills on seawater by showing video footage or some pictures from the Internet. Ask students to explain the damage that oil spills can cause, particularly to seabirds. Discuss how oil spills are usually cleared up.

Provide groups with a washing-up bowl containing water. Add about 3–5 tablespoons of cooking oil to the top of the water. Challenge students to find a way of cleaning up the oil. Ideas may include soaking up the oil in absorbent materials, placing a circle of material such as a plastic around it and then making the circle smaller, or adding an insoluble (in water) solid such as gypsum or chalk to it that coagulates the oil and then sinks in the water. Test the ideas and compare them. Which is the most effective? Which idea could be scaled up to deal with a large oil spill. What are the environmental advantages and disadvantages of each idea?



Removing stains Challenge students to investigate which commercially available solvents are best for removing different stains from cotton cloth. Points to consider are the substance that makes the stain (e.g. fat, cola, coffee, mud), how to make the stains the same size, how to devise a fair method for comparing the effect of the different solvents, how to judge how effective they are. Ask them to predict the outcome based on their knowledge of solvents. Ask them to summarise both their predictions and their results in a table and to consider how far the evidence justified their predictions.

Safety: Some solvents are flammable and others may give off an unpleasant vapour. Use in a well-ventilated room and with no naked flames.

Enquiry skills 6.1.1–6.1.3

Additional activities for more advanced students More advanced students can explore the idea of different layers of solvents further through a number of simple activities (which can be done either as demonstrations or as group work) that raise questions demanding answers. • Pour water and cooking oil into a jar to form two layers. Into the mixture drop a piece of metal

(such as a coin or nail), a cork and a small tomato or slice of green bean. Note how far they sink and explain the observation.

• Pour some syrup into a jar to a depth of about 2 cm. Carefully pour some glycerine (glycerol) down the back of a spoon onto the top of the syrup. Do not allow the layers to mix. On top of the glycerine add a layer of water (which can be coloured with food dye so that it can be seen better). On top of the water pour a layer of cooking oil. Why do the miscible liquids stay in layers and do not mix much even if they are left overnight?

• Fill two cups with tap water. Stir about a tablespoon of salt into one and place an uncooked egg in each. Explain the difference.

• Very carefully pour tap water onto the top of salt water in a large glass mug. Carefully place an egg in the mug (one of the liquids could be coloured). Where does the egg float and why?

• Make a simple hydrometer from a short pencil weighted at one end and use it to compare densities of different liquids.

• Discuss the Plimsoll line on ships.

These activities introduce the idea of the density of different liquids in an intuitive way. At this stage, the mathematical concept of density is probably too advanced for most students, but the word can be used.


Assessment


Think about how you would compare how long tea from different teabags takes to dissolve.

What are the variables in this investigation and which would you keep constant and why?

What will be your dependent and your independent variables?

One way of comparing how fast the tea dissolves is to use a simple turbidity meter. Draw a cross on a piece of paper, place it under the beaker of water. Place the teabag in the water and find out how long it takes for the liquid to become so dark that the cross cannot be seen from above. Explain why this helps make the test more accurate.

Draw a table suitable for displaying the results of your investigation.

Enquiry skill 6.1.1

Complete the following sentence. When a solid dissolves in a solvent, a _________ is formed.

A beaker contains water. It is on a balance. The balance reads 200.0 g. Nisreen adds 10.5 g of salt to the water. The salt dissolves.

When all the salt has dissolved, what is the reading on the balance? _________ g

Nisreen wants to get all the solid salt back from the water. Describe how she could do this.

QCA Key Stage 3 science, level 4, Q97.A1.06

a. The table shows the solubility of three gases at two different temperatures. The solubility is shown as the volume that will dissolve in 1 dm3 of water.

Use the information to answer the following questions.

i. Which gas is least soluble at 20 °C?

ii. How does a rise in temperature affect the volume of a gas that will dissolve in water?

iii. If you leave a glass of cold water on a sunny windowsill during the day, you often see bubbles of gas forming next to the glass. Explain this observation.

b. Explain why it is important to us that oxygen will dissolve in water.

Gas Volume dissolved at 20 °C

Volume dissolved at 50 °C

Ammonia 680 000 cm3 190 000 cm3

Carbon dioxide

840 cm3 320 cm3

Oxygen 27 cm3 16 cm3

Assessment

Set up activities that allow students to demonstrate what they have learned in this unit. The activities can be provided informally or formally during and at the end of the unit, or for homework. They can be selected from the teaching activities or can be new experiences. Choose tasks and questions from the examples to incorporate in the activities.

You are asked to make a solution of a soluble solid that is in the form of lumps the size of pebbles. List three ways that you could use to speed up the rate at which the solid dissolves.

Unit 6M.1



Making pure substances from mixtures

About this unit This is the second of four units on materials in Grade 6. This unit builds on ideas introduced in Units 5M.1 ‘Water’ and 6M.1 ‘Solubility’. Ideas from this unit are developed further in Unit 7M.2 ‘Mixtures, compounds and elements’.





Expectations

Previous learning To meet the expectations of this unit, students should already be aware of the processes involved in the preparation of household water supplies in Doha and how waste water is treated. They should distinguish between solids that are soluble in water and those are insoluble. By the end of the unit, students know that dissolving can be used to separate a soluble from an insoluble solid using filtration and evaporation and that crystallisation is used to obtain pure samples of substances from solution. They list everyday examples of filtration. They conduct systematic investigations, make predictions from and identify patterns in data and observations, and consider whether evidence supports a conclusion, prediction or hypothesis. They make simple models

Students who progress further explain crystal growth and regular cleavage in terms of the regular arrangement of particles.

Resources The main resources needed for this unit are: • hand lenses • chemicals for making crystals, such as copper sulfate, alum and chrome

alum • mechanism for heating solutions • Internet access

Key vocabulary and technical terms Students should understand, use and spell correctly: • separate, filter, filtrate, filtration, residue • soluble, insoluble • crystal, regular, crystallise, evaporate

UNIT 6M.2 6 hours





5.9.4 Describe the process of getting drinking water from seawater in Qatar and know that the distillation process uses waste heat from producing electricity and that the steam is condensed using seawater as a coolant.

6.11.3 Know that a solute can often be recovered by evaporating the solvent, which can then be recovered by condensing it.

7.12.1 Explain how the processes of solution, filtration, evaporation and distillation can be used to make pure substances from mixtures and cite common examples of the use of each.

5.9.3 Investigate how waste water is treated in Doha.

6.11.4 Separate insoluble solids from a liquid by filtration and state everyday examples of filtration, such as coffee making, sewage works and water purification.

6.11.5 Use crystallisation to obtain pure samples of a solute from a solution.

6.1.1 Plan investigations, controlling variables and collecting an appropriate range of evidence, identify patterns in observations and data, draw appropriate generalised conclusions and test predictions.

4 hours

Making pure substances from mixtures

2 hours

Crystals

6.3.1 Make models from everyday materials to help explain scientific phenomena and technological solutions.

Unit 6M.2


Activities


Separating solids Set an introductory task to the class. Give them a mixture of fine sand, rice and marbles and ask them to devise mechanisms for separating them quickly and easily. Have ready a variety of materials that can be used as sieves (e.g. tea strainers, shade netting, coarsely woven cloth). Ask them to predict the result of their mechanism and then test it.

Extend the scope of this exercise by adding some iron objects (e.g. iron filings, paper clips) that can be separated using a magnet.

Enquiry skill 6.1.2


Filtration in everyday life Make a cup of tea from a teabag. Discuss what happened as the tea brewed. Open the bag and look at the tea inside and look carefully at the bag using a hand lens. Look also at some coffee filter papers. Ask why the soluble particles get through the paper but the solid remains behind.

Ask students to bring in examples of filters that are used in everyday life and make a display of them that shows what they are used for. Vacuum cleaners and cars use filters. Ask them to find examples of industrial filters on the Internet. For example, suggest that they find out how the seawater used in industrial plants in Qatar is filtered and obtain photographs of some of the filters.

ICT opportunity: Use of the Internet.

Separating sand from salt Take samples of sand and salt and mix them in front of the class. Challenge groups to devise a way of separating them again to obtain pure samples of both. If necessary, give help by reminding them that salt is soluble but sand is not. They should decide to filter the mixture and then evaporate the filtered liquid.

The sand is left as the residue in the filter paper and the salt can be recovered by evaporating the water from the filtrate. Students should be familiar with these words.

Have useful equipment ready (e.g. coffee filters, funnels, jam jars). Provide hotplates or a similar heat source but use only heatproof glassware on it

Safety: Tell students not to use taste as a test for the pure salt.

Model sewage works sand filter Recall work on sewage treatment from Grade 5. Point out that most water purification plants use sand filters as a cheap and effective way of cleaning water. Get students to build and test a model sand filter made from an inverted plastic bottle with the bottom cut off to make an elongated funnel. Ask them to experiment with the design, which must have some kind of porous plug in the funnel end and be filled with stones and sand graded from large to small towards the top of the funnel. Tell them to test the design with both suspensions and sugar solution to investigate its effectiveness.

A simple test for sugar (such as Clinistix) can be used to test the solution that goes in and that coming out. It is unlikely that a difference will be noted. The role of bacteria in sand filters should not be mentioned at this stage unless it has been covered in life science.

Enquiry skill 6.3.1

4 hours

Making pure substances from mixtures Separate insoluble solids from a liquid by filtration and state everyday examples of filtration, such as coffee making, sewage works and water purification.

Know that a solute can often be recovered by evaporating the solvent, which can then be recovered by condensing it.

Make models from everyday materials to help explain scientific phenomena and technological solutions.

Recovering the solvent Recall from Grade 5 the recovery of a solvent from a solution by distillation. Challenge the class to develop effective ways of making pure water from dirty water in the classroom. Allow students to try out their ideas for cooling the steam produced. This will lead into the use of the Liebig condenser in Grade 7.

Safety: Take necessary precautions when heating water. If a delivery tube is used, ensure that precautions are taken against ‘sucking back’.

Unit 6M.2



Looking at crystals Make a classroom display of different kinds of crystals. Include examples of natural crystals and synthetic ones. Allow students to obtain pictures of crystals from the Internet.

Ask students to look at and draw some common crystals such as salt and sugar. Tell them to make cardboard models of some of the common crystal shapes, such as the cube and the octahedron. Question the class to ensure that they have seen that: • the sides of crystals are flat and smooth; • crystals have a regular shape; • all crystals of the same substance have fundamentally the same shape.

Ensure that they understand that crystals are a pure single substance.

Obtain a sample of a large crystal that can be cleaved easily (such as Iceland spar or mica). Demonstrate that when crystals are cleaved the new faces are always parallel to the old ones. (If Iceland spar is used, draw attention to the strange phenomenon of double refraction displayed by this substance, which can be explained in a later grade.)

More advanced students my wish to explore this in terms of particle theory, which will be covered more fully in Grade 7. A particle model of a crystal can be made from polystyrene spheres to show cleavage.


Mathematics: 3D symmetry is not covered in mathematics until Grade 7.

Crystals from seawater Repeat work from Grade 5 on the evaporation of seawater. Allow groups to evaporate seawater slowly and look carefully at the residue. They should note the shapes of any crystals and whether all the crystals are the same shape. Seawater contains a mixture of solutes, but the main one is sodium chloride, which has an unmistakable cubic shape.

Growing crystals Ask students, individually or in small groups, to prepare a saturated solution of copper sulfate in hot water, filter it and allow it to cool and evaporate. Small copper sulfate crystals will form that can be used as seeds to grow larger crystals. Tell students to hang their seed on a nylon thread in a jar of the saturated solution and leave in a room where the temperature does not fluctuate. Ask them to note what happens and to explain the growth of the crystal.

Some students may wish to try other solutes: aluminium potassium sulfate (alum) and chromium potassium sulfate (chrome alum) make good crystals.

Suggest to more advanced students that they grow a chrome alum crystal (which is almost black in colour) and then continue growing it in a potassium alum solution. Challenge them to explain in particle terms how this is possible.

Keep a supply of saturated copper sulfate solution and top up the jars as the water evaporates and the crystal grows larger.

Good crystals should be varnished when they have grown, using colourless nail varnish, to prevent water loss leading to a powdery surface.

Safety: Copper sulfate is mildly poisonous.

2 hours

Crystals Use crystallisation to obtain pure samples of a solute from a solution

Crystal gardens An additional classical activity that is interesting and motivating is to drop a few coloured crystals into a 40% solution of sodium silicate (‘water glass’) in a glass container. The crystals grow in vertical strands. The explanation involves osmosis and is beyond this grade.


Assessment


Jamal put 10 cm3 of water and 3 g of a different solid into each of four test-tubes. He shook each test-tube. The drawing shows the test-tubes after 10 minutes.

a. Why can the sugar and salt no longer be seen in test-tubes A and C?

b. If one of the solids was a mixture of salt and sand, what would Jamal see in the tube after 10 minutes? How would Jamal get from the tube (i) some pure sand and (ii) some pure salt?

A sugar B limestone C salt D sand

Filtration using the equipment shown can be used to separate which materials?

A. A solution of copper sulfate and water.

B. A solution of sodium chloride and water.

C. A mixture of alcohol and water.

D. A mixture of mud and water.

E. A mixture of sand and sawdust.

TIMSS Grade 7, 1995


Describe how you would separate the following mixtures

A. A mixture of sand and iron filings.

B. A mixture of sand and pebbles.

C. A mixture of sand and salt.

D. A mixture of sand and water.

Unit 6M.2



Changing materials

About this unit This unit is the third of four units on materials for Grade 6.





Previous learning To meet the expectations of this unit, students should already be familiar with how we use and change everyday materials, such as cooking raw food and making the common items that we have around us. They should also recognise that most of these changes are permanent but that others, such as changing water into ice or dissolving salt, are temporary.

Expectations By the end of the unit, students distinguish between reversible and irreversible changes. They know that mixing materials together or heating materials can cause them to change temporarily or permanently. They understand that reversible, temporary, changes are usually physical, whereas irreversible, permanent, changes are usually chemical and new materials are formed.

Students who progress further recognise that common changes such as rusting and the running down of a cell are chemical changes involving the preparation of new substances by a process that is usually irreversible and also usually involves an energy change.

Resources The main resources needed for this unit are: • variety of common household foodstuffs and chemicals • investigation planning poster • suitable containers (e.g. jam jars) for studying the reactions • batteries, connecting wires, copper and zinc strips, bulbs, carbon rods • video clips of firefighters putting out fires

Key vocabulary and technical terms Students should understand, use and spell correctly: • dissolve, soluble, insoluble, evaporate, filter • permanent change, temporary change • reversible change, irreversible change • weathering, extraction • acid • electrolysis, cell

UNIT 6M.3 9 hours





5.10.1 Give examples of ways in which we change materials: for example, cooking, firing clay, setting cement. Know that these changes are permanent.

7.12.9 Know that compounds can react chemically with each other to form new compounds.

5.10.3 Give examples of the ways we can change material temporarily: for example, making objects out of clay without firing, dissolving table salt, melting a candle.

7.12.8 Know that elements combine to form compounds and that the properties of compounds are different from the properties of their constituent elements.

5.14.3 Test whether a material is a good or bad conductor of electricity and recognise that metals conduct electricity whereas non-metals do not.

5.10.5 Classify common changes as temporary or permanent.

6.12.1 Distinguish between reversible and irreversible changes and know that reversible ones are physical and irreversible ones involve chemical changes in which new substances are formed.

5 hours

Adding materials to water

4 hours

Some chemical reactions

5.9.6 Know that water is a good solvent but that not all substances dissolve in water.

6.12.2 Know that when substances are added to water, some will react while others either dissolve or remain suspended.

7.12.1 Explain how the processes of solution, filtration, evaporation and distillation can be used to make pure substances from mixtures and cite common examples of the use of each.

Unit 6M.3


Activities


Introduction Recall work done in Unit 6M.1 on what substances dissolve in water. Ask the class whether a number of common substances are soluble in water or not (e.g. salt, sugar, pepper, sand, butter). Be prepared to demonstrate if necessary.

Then ask the class what they think happens to a substance like salt when it dissolves. There may be few very clear ideas but direct the discussion towards whether or not the change is temporary or permanent and how they might find out.


Adding things to water This topic will last two double sessions or more. In it students will work in groups to investigate what happens when a variety of substances are added to water. In order to complete the investigation, they may have to leave the vessel until the next lesson to see what happens when the water evaporates. By the end of the session they should be able to distinguish between substances that are very soluble, slightly soluble and insoluble. They should also be able to distinguish between substances that dissolve in water and substances that react with water – the first change is temporary and reversible whereas the second is permanent and irreversible.

Groups will need suitable equipment to test all the substance. This means very many jam jars or similar cartons and a pen for labelling them. Many will have to be left for some time to study the change or to see whether the change is reversed when the water evaporates. Encourage students to work with small quantities – they will be able to see any changes just as well and the evaporation process will be much faster.

Remind students that they may have to filter some solutions (Unit 6M.2) if there is a residue, to find out what has dissolved.

Substances that can be used include: • stomach powder, baking powder, flour, sugar,

salt, pepper, cooking oil; • soap, detergent, iron nail, aluminium foil,

sand, plaster of Paris, steel wool, concrete, glass, plastic;

• cloth marked with water soluble dye and water insoluble dye, oily cloth.

5 hours

Adding materials to water Distinguish between reversible and irreversible changes and know that reversible ones are physical and irreversible ones involve chemical changes in which new substances are formed.

Know that when substances are added to water, some will react while others either dissolve or remain suspended.

Make sure students plan how they are going to carry out the investigation beforehand and ask them not to start until they have made their plan and presented it to you for comment. They may wish to use the investigation planning poster.

Ask them to watch very carefully when they add the substances to water and to note any changes they observe. One possible change is the evolution of heat (plaster of Paris), but do not warn them in advance.

After they have finished, spend some time drawing some conclusions by discussing what happened to each substance. Ask students to make a summary table in their books which classifies the changes as temporary or permanent or no change.

Enquiry skills 6.1.1, 6.1.2, 6.2.1

Unit 6M.3



Using water to change materials Water can be used in other ways to change materials. This series of activities investigates a number of different ways water can do this. Some of these are investigations that require some equipment that the school may not have in class sets. Set up the investigations as a circus and ask the groups to rotate around them.

Weathering Have a number of smooth pebbles available for students to feel. Ask groups to recall from earlier work how they became smooth.

Soak a small piece of concrete or porous rock (e.g. limestone of sandstone) in water, preferably overnight. Ask groups to take it out of the water and put it in the freezing compartment of the fridge. After a few days they should take it out, allow it to thaw and examine it.

Fill a plastic film canister completely to the top with water. Put the top on carefully so that no air gets in. Put the canister in the freezer and look at it again after a few days.

This activity demonstrates a very unusual property of water: it expands when it freezes. This is clearly shown in the case of the film canister. The piece of concrete or porous stone may or may not have changed (pieces crumbling off). Even if there is no change, describe the action of freezing water in weathering rocks. Ask students to suggest how this expansion might cause rocks to crack.

Extracting colour Take some colourful leaves or petals and put them in a suitable glass container (e.g. a glass teacup). Pour hot water on the material and then stir it and filter (or scoop out the remaining solid). Look at the liquid. Leave it to evaporate and study the extract.

Extracting scent Gently heat a mixture of finely cut lemon or orange skin (just the yellow or orange part) with a small amount of water in a boiling tube fitted with a long delivery tube. Collect the first drops from the delivery tube and smell them. Look carefully at the liquid you have collected. You may see that it is cloudy or that there are two layers. This technique can be used to extract many scents, and some students may wish to try it with materials such as jasmine or lavender flowers.

Safety: Exercise appropriate supervision of activities that involve heat.

Putting out fires Show students some video clips of firefighters putting out fires with water. Challenge them to explain what is happening and why water puts out fire. This will be taken further in the next unit.

As before, discuss all the observations with the class and decide in each case whether the change has been temporary or permanent. Ensure that they realise that the discussion should focus on the chemicals in the objects they have used and not on the objects themselves. So it should be made clear that although the lemon or orange skin has changed irreversibly, the chemical in it that causes the smell has not been changed during the distillation.

You should be able to find some suitable video clips on the Internet.

Classify changes Finally, ensure that the students have classified all the changes they have observed as either temporary or permanent. At this stage, you can start referring to permanent changes, where new substances are made, as chemical changes and temporary changes, in which no new substances are made, as physical changes.



Adding things to lemon juice As a starter, pour some vinegar into a film canister until it is about half full. Add some baking powder, quickly put the top on, shake it and put it down upside down. It will explode harmlessly.

Introduce the idea of an acid as a class of chemical. Tell students that vinegar, fruit juices such as lemon juice and sharp tasting sweets all contain acids, and that acids give them all their sharp taste. In this activity, the groups will add the same materials as they used before to an acid such as lemon juice or vinegar.

As before, tell students to make a note of anything that happens.

Discuss the results with the class and, as before, classify the observed changes as temporary or permanent. During this discussion, list the observations that led the class to conclude that a permanent change had taken place (e.g. the production of a new substance such as rust or a gas, the complete irreversible disappearance of the original material).

Safety: Keep students some distance away from the film canister.

Using electricity to change things Recall work in Grade 5 on electrical circuits, especially conductivity testing. Demonstrate a suitable circuit containing two nails or copper or carbon rods that could be used to test conductivity.

Let each group test the conductivity of water and a number of solutions, particularly strong salt solution, and also an acid. They will find that the salt solution and the acid both conduct electricity. They should also notice bubbles at the electrodes, and they should be able to smell chlorine in the case of the salt solution. Write down the changes and classify them as temporary or permanent.

Remind students that cells and batteries eventually run down when used. Recall that this is because a chemical change takes place inside them. To investigate this, ask each group to prepare a cell by pushing clean shiny strips of copper and zinc into a lemon. Connect a low-voltage bulb between them. Whenever the bulb goes out, tell them to move the metal strips around a bit until it lights again. After a time, ask them to look at the metal strips, particularly the zinc one. They will notice signs that it is being eaten away by an irreversible chemical reaction as the lemon cell runs down.

What does bleach do? Place a number of substances in some concentrated bleach solution and leave for several hours. Either do this as a demonstration or let groups of students do it, with due regard for safety. As before, discuss any observations and classify changes as temporary or permanent.

Safety: Do not get bleach on hands or clothes. Wash splashes off immediately with much water.

Suitable substances include a cloth coloured with inks and oil, pieces of newspaper, wood, metal.

4 hours

Some chemical reactions Distinguish between reversible and irreversible changes and know that reversible ones are physical and irreversible ones involve chemical changes in which new substances are formed.

Know that when substances are added to water, some will react while others either dissolve or remain suspended.

How do we know if a chemical change has occurred? Discuss with the class how they recognised when a permanent change had taken place. List the correct and most useful responses on the board or OHP. These might include: • a gas is given off; • there was permanent colour change; • a new substance (e.g. rust) was formed and could be seen; • the liquid became warm; • the solute could not be recovered when the water was left to evaporate.

Tell students to copy these responses into their books as a general conclusion to the unit.


Assessment


Ghada added some substances to water and stirred them. She noted her observations in a table.

Substance Observation

1 Sugar Disappeared

2 Salt Disappeared

3 Sand Remained at the bottom

4 Stomach powder Bubbles of gas given off

5 Flour Liquid turned white and eventually the white substance collected at the bottom

a. In which case(s) were there chemical changes? Explain your answer.

b. Give two instances where the change could have been physical or chemical. Describe one test that she could carry out to determine which kind of change had taken place and explain the expected result of the test both changes.

c. How could she recover the residues in samples 3 and 5?

The two lists below contain raw materials and substances made from them. Draw lines to connect each raw material to the substance produced from it. On each line write whether the change is a physical or a chemical one.

Raw material Substance produced

Clay Glass

Ore Metal

Sand Paper

Seawater Pottery

Wood Salt


Classify the list of changes as physical or chemical.

A. Making yoghurt from milk.

B. Making drink cans from aluminium sheet.

C. Boiling water in a kettle.

D. Boiling an egg.

E. Making a cup of tea.

F. Using a torch cell.

G. Burning a candle.

Add two more common changes to the list, one physical and one chemical.

Unit 6M.3



Heating and burning

About this unit This unit is the fourth of four units on materials for Grade 6. This unit requires an understanding of the content of the other three.

The unit is designed to guide your planning and teaching of lessons on physical processes. It provides a link between the standards for science and your lesson plans.




Previous learning To meet the expectations of this unit, students should already be able to distinguish between a temporary and a permanent change and have an understanding of the three states of matter.

Expectations By the end of the unit, students distinguish between reversible and irreversible changes. They know that mixing materials together or heating materials can cause them to change temporarily or permanently. They understand that reversible, temporary, changes are usually physical, whereas irreversible, permanent, changes are usually chemical and new materials are formed.

Students who progress further list criteria for distinguishing between physical and chemical changes, including detecting the heat of reaction. They know that when a substance burns, it combines with one or more of the gases of the air and that if this supply is cut off, the substance will stop burning.

Resources The main resources needed for this unit are: • for heating: burner, flameproof mat, tongs, test-tube, test-tube holder and

rack, tripod, tin lid • candle, hand lens, jam jars • different types of fire extinguishers, smoke alarm, fire blanket, fire bucket • variety of common substances from around the home • safety screen

Key vocabulary and technical terms Students should understand, use and spell correctly: • candle, wick, gas • fire extinguisher, smoke alarm • reversible change, irreversible change • physical change, chemical change

UNIT 6M.4 7 hours





5.10.1 Give examples of ways in which we change materials: for example, cooking, firing clay, setting cement. Know that these changes are permanent.

6.12.1 Distinguish between reversible and irreversible changes and know that reversible ones are physical and irreversible ones involve chemical changes in which new substances are formed.

5.10.2 Describe the differences between the substances before and after a permanent change.

7.12.9 Know that compounds can react chemically with each other to form new compounds.

3 hours

Burning

4 hours

Heating different materials

5.10.5 Classify common changes as temporary or permanent.

6.12.3 Know that heating can bring about temporary, physical, changes in some materials and permanent, chemical, changes in others. Distinguish between heating and burning.

7.13.3 Know that when a substance burns, it combines chemically with the oxygen in the air and that the overall mass of the product(s) is greater than the original mass of the material.

Unit 6M.4


Activities


Introduction This unit follows directly on from Unit 6M.3 and the summary at the end of Unit 6M.3 is an appropriate introduction. If necessary, ascertain students’ understanding of the characteristics of physical and chemical changes by asking them to produce a concept map around the concept of change. This will be re-examined at the end of the unit.


3 hours

Burning Know that heating can bring about temporary, physical, changes in some materials and permanent, chemical, changes in others. Distinguish between heating and burning.

Studying a candle flame This is an exercise in observation and deduction. It is best done in pairs so that the experimenters can discuss their ideas but still can get close to the candle. Ask students to look first at the candle before it is lit, then as a flame is applied to the top of the wick to light it and finally while it is burning. Provide a hand lens but caution the class not to put their face too close to the flame.

Tell them to write down all their observations.

Ask them to attempt to explain what they think might be happening to the candle and in the flame that explains all their observations.

Encourage them to think of additional activities they may wish to do to find out more about the burning flame. Possible ideas are: • Place a clean cold mirror of glass briefly above the flame and then look at what collects on it. • Take a small matchstick (remove the striking end) or toothpick and slide it briefly in and out

across the flame just above the wick to find out something about the cone-shaped centre of the flame. (They will observe, if they do it carefully, that the part of the toothpick in the centre of the flame is not charred whereas the parts at the edges are.)

• Place an inverted jam jar high over the flame.

Collect observations from around the class. Help students try to explain them. Key explanations that should emerge include: • The wick does not burn, molten wax on it is burnt and more is sucked up to replace it. (How

could this be demonstrated? Faraday thought of a way of stopping it.) • Water is produced when the candle burns. • A supply or air to the flame is needed for it to continue burning. • Some soot is often produced when the candle burns. • The cone in the centre of the flame is unburnt wax vapour. • The wax burns with a blue flame near the bottom and yellow near the top. (Use a gas burner

to demonstrate how varying the amount of air getting in affects the colour of the flame – the yellow flame is produced when there is not enough air reaching the fuel.)

This topic was first developed by Michael Faraday in a series of public lectures in the 1860s and later published as The Chemical History of a Candle. It has since been a part of science schemes of work for a century and a half.

Safety: Warn students that they must not place a glass thermometer in a candle flame; it will break explosively.

Unit 6M.4



What does a substance need to burn? Ask each pair to burn three small candles under jam jars of different sizes and find out how long the flame takes to go out in each case. Discuss the results and draw conclusions about the need for air by anything that is burning.

Fire extinguishers Show a collection of different kinds of fire prevention equipment, including extinguishers that use foam, water, dry powder and carbon dioxide. Demonstrate the dry powder or the carbon dioxide extinguisher outside on a small fire.

Draw attention to the safety pin that must be removed before the extinguisher can be used and discuss the reason for this. Show how the extinguisher should be directed at the base of the fire to put it out. Discuss how fire extinguishers work by smothering the fire so that air cannot get to it.

Discuss the suitability of different types of extinguisher for different types of fire. In particular, note the reasons why a water extinguisher should not be used on an electrical fire.

Safety: Students should be kept a safe distance from the fire demonstration.

Fire hazards and safety Ask students what fire safety precautions they have seen in the school and also what they have at home. Ask them if they have ever seen any fire hazard notices and, if so, where. They will probably recall one at a petrol station. Show them one.

Demonstrate a simple smoke alarm by burning some string near it. Open the alarm to show the battery and show students how to test the alarm so they become familiar with its operation.

Show how a fire blanket and a fire bucket should be used.

Ask the class whether they know what they should do if there is a fire in their classroom. If they do not know, organise a fire practice.

Teachers who have been trained to do so safely could demonstrate (a) what happens when someone attempts to extinguish a ‘chip-pan’ kitchen fire with water and (b) how to put out such a fire quickly and safely. Those who have not been trained should use a video clip. Both these demonstrations should be conducted outside a safe distance from the students.

The matters covered in this section could be covered by inviting the fire prevention officers to visit the classroom.

Safety: These demonstrations can be dangerous; they must only be performed outside, a safe distance from students, by a properly trained person.



Recall earlier work Ask the class to recall the work they have done heating different material in Grade 5. Be prepared to demonstrate some if their memory is weak. In particular, recall the effect of heat on uncooked foodstuffs and on substances such as clay, where heat caused permanent changes.

Heating different substances Ask students, in groups, to find out the effect of heat on a variety of substances. Instruct them on the most appropriate way to heat each substance (e.g. held in tongs, in a tin lid on a tripod, or in a test-tube). Explain all the necessary safety precautions and stop any group, at any time, that is not observing them.

Demonstrate the action of a flame on methylated spirits and cooking oil. Ensure that students are watching from a safe distance and use a safety screen.

Require all students to make a comprehensive table of their observations. At the end of the session, ask them to share their observations. Be ready to repeat any as a demonstration if you feel that many in the class missed an important point.

Finally, ask the class to classify the observations as temporary or permanent changes.

Suitable materials to use include: paper, salt, sugar, wood, candle wax, chocolate, ice, water, egg, cake mix, flour, dough, bread, steel nails, aluminium, copper.

Safety: Safety goggles should be worn in all lessons on materials but they are particularly important in this lesson. Perform heating demonstrations behind safety screen.

Enquiry skills 6.2.1, 6.3.3

Reversible and irreversible changes

Ask students to prepare a summary table showing which changes they have met in this unit were reversible and which irreversible. Ensure that they understand that irreversible ones are those in which new chemical substances are formed and that these are chemical changes.

Enquiry skill 6.2.1

4 hours

Heating different materials Distinguish between reversible and irreversible changes and know that reversible ones are physical and irreversible ones involve chemical changes in which new substances are formed.

Concept map on changes Return to the concept map started at the beginning of this unit, which should summarise all the previous work done on materials in Grade 6. Ask students to add to their concept map so that it includes the following words, and any more that they wish to add. heating, cooling, dissolving, melting, freezing, condensing, evaporating, burning, reversible,

irreversible, chemical, physical, water, steam, ice, candle wax, gas, wood, paper, salt.

Enquiry skill 6.2.3


Assessment


Ibrahim heated a number of substances using a burner. He recorded what he observed in a table.

Substance Observation

1 Sugar Turned to a liquid

2 Salt No change

3 Sand No change

4 Piece of wood shaving Caught fire leaving a grey residue

5 Egg white Turned white

6 Ice Turned to a liquid and then boiled

a. In which case(s) were there chemical changes? Explain your answer.

b. Give two instances where the change could have been physical or chemical. Describe one test that he could carry out to determine which kind of change had taken place and explain the expected result of the test for both changes.

a. When a candle burns, the wax changes into products that are gases. Explain how you could detect one of those products. Explain what it is.

b. The central cone of a candle flame contains a gas that is not burning. What is the gas and why is it not burning?

c. If two identical candles are lit and one is then covered with a large jam jar and the second with a small one they both will go out. Which one will go out first? Explain why they both are extinguished and why one is extinguished before the other.

a. There are many different kinds of fire extinguisher, but they all put out the fire in the same way. Explain how the material in a fire extinguisher puts out the fire.

b. What is the best way of putting out the following fires? Explain your answer:

i. A fire in a car.

ii. A fire in a kitchen caused when cooking oil catches fire.

iii. A pool of burning methylated sprits.


Write flow charts showing all the changes in the following processes. Indicate whether each change is physical or chemical.

a. Making a loaf of bread starting with grains of wheat.

b. Making a pottery cup from clay.

c. Burning newspaper made from trees.

Unit 6M.4

265 | Qatar science scheme of work | Grade 6 | Unit 6E.1 | Earth and space 1 © Education Institute 2005

GRADE 6: Earth and space 1

The movement of the Earth and the Moon

About this unit This unit is the only unit on Earth and space in Grade 6. The unit requires some knowledge of light (Unit 6P.2). It forms a basis for further studies of the Solar System in Grade 8.

The unit is designed to guide your planning and teaching of lessons on Earth and space. It provides a link between the standards for science and your lesson plans.




Previous learning To meet the expectations of this unit, students should already recognise that day and night are caused by the rotation of the Earth on its axis. They also should understand that the Sun is the source of light by day and that we see the Moon because it is illuminated by sunlight.

Expectations By the end of the unit, students know that the Sun and stars are light sources but that the Moon is an illuminated object that reflects light from the Sun. They know the shape and approximate relative sizes of the Sun, the Earth and the Moon. They know that the revolution of the Moon around the Earth causes the phases of the Moon. They know the causes of the tides and of eclipses. They know that the Earth orbits the Sun once every year, why the Sun appears higher in the sky in the summer than in the winter.

Students who progress further account for some observed differences between the Earth and the Moon. They know why summer is hotter than winter. They explain the origins of, and differences between, the Saudi Islamic calendar and the Gregorian calendar. They distinguish between the umbra and penumbra in a shadow and relate it to lunar eclipses.

Resources The main resources needed for this unit are: • video and still photographs of the Sun and Moon downloaded from the

Internet • a ‘Moon diary’ consisting of records by students to be completed before

the teaching of the unit (see the third section of this unit ‘The phases of the Moon and eclipses’)

• Internet access

Key vocabulary and technical terms Students should understand, use and spell correctly: • Sun, sunspots, solar, solar flares • Moon, lunar, crater, Moon phases • light source, reflected light • year, month, day, night, seasons, calendar • eclipse, shadow, umbra, penumbra

UNIT 6E.1 12 hours





4.13.1 Know that the Sun is a source of light and that this causes shadows of objects.

6.13.1 Know that the Sun and stars are light sources and that the Sun is the source of our daylight.

8.15.4 Know that the Sun is a star and that, like all stars, it radiates light and heat.

6.16.3 Know that we see light sources because light travels from them to our eyes and that we see objects that are not light sources because they are illuminated by light sources and light is reflected into our eyes.

6.13.2 Explain that we see the Moon at night because it is an illuminated object that reflects light from the Sun.

6.13.3 Know that the Sun, the Earth and the Moon are all roughly spherical objects in space and know their approximate relative sizes.

6.13.4 Know that the Moon revolves around the Earth once every 28 days and show how this causes the phases of the Moon.

6.13.5 Know that the gravitational attraction of the Moon and the Sun on the Earth’s seas causes the tides.

6.13.6 Know the causes of eclipses of the Sun and the Moon.

4.13.3 Explain how the movement of the Earth on its axis causes day and night.

6.13.7 Know that the Earth orbits the Sun once every year.

6.13.8 Understand why the Sun is higher in the sky during the summer than in the winter and why it is hotter in summer than in winter.

8.15.1 Explain night and day, eclipses, seasons, tides, and phases of the Moon in terms of the movement and relative sizes of the Sun, Earth and Moon.

5 hours

The Sun–Earth–Moon system

3 hours

The movement of the Earth

4 hours

The phases of the Moon and eclipses

6.3.1 Make models from everyday materials to help explain scientific phenomena and technological solutions.

7.2.3 Know that our understanding of science has accumulated and changed over time and is the result of work in many countries

Unit 6E.1


Activities


Before studying this unit, students need to understand the difference between an object that we see because it is a source of light and those that we see by reflected light. This is covered in Unit 6P.2.

Use the Internet throughout this unit as a source of information and illustrative photographs.

Ask students to make flip books of other solar events, such as sunspots – set this as a homework task for more advanced students. Sunspots can often be observed on the surface of the Sun using firmly clamped binoculars to project the image of the Sun onto a sheet of white card. Discuss the origins and nature of sunspots with more advanced students. Ask students for their ideas about the approximate sizes of the Sun, Earth and Moon and the distances between them (you could tell them that the diameter of the Earth is about 12 000 km and ask for their ideas about the other dimension and distances). Make a note of some of their answers and, at the end of this topic, compare them with the actual values.

Note that the diameter of the Sun is 109 times the diameter of the Earth.


5 hours

The Sun–Earth–Moon system Know that the Sun and stars are light sources and that the Sun is the source of our daylight.

Explain that we see the Moon at night because it is an illuminated object that reflects light from the Sun.

Know that the Sun, the Earth and the Moon are all roughly spherical objects in space and know their approximate relative sizes.

The Sun Display a collection of photographs of the Sun that show it as source of light and heat. Some speeded-up video clips of solar flares give a vivid impression of the activity of the Sun. Ask advanced students to access the daily report on SOHO website and report on any interesting features related to the solar ‘weather’ that they note. Obtain still photographs of a solar flare as it erupts and print out several sets on card. Divide students into groups, give each group a set of the cards and ask them to make a solar flare flip book. Flares typically take several hours to erupt and die down, and the flip book can show this speeded up. Ask the class to make an estimate of the size of the flare. Discuss possible origins of flares. The details will be beyond students at this stage, but make sure they understand that the Sun is very hot and that huge masses of material can be rapidly thrown into space through distances many times the diameter of the Earth. Students will compare it to a huge ball of fire, but point out that it must be different because a fire requires air, and also the temperature of a fire is less than 1000 °C but the temperature of the surface of the Sun is about 6000 °C.

Discuss with students the fact the Sun is a star. Ask for reasons why it is much brighter. It appears brighter than other stars because it is much closer (about a million times closer than the next nearest star). Ask them what the Earth might be like if the only light and heat reaching it came from the other stars. This should lead to an understanding that the light and heat from the Sun are essential to life on Earth.

The website of the Solar and Heliospheric Observatory (SOHO) satellite observatory that is orbiting the Sun is a useful source of information and pictures (http://sohowww.nascom.nasa.gov). NASA maintains a daily report of significant details of solar activity.

The SOHO webpage has some sequential solar flare photographs. Another good source is the Photo Gallery of Crosby Ramsey Memorial Observatory of the Maryland Science Centre, http://www.mdsci.org/exhibits/observatory/photo/ index.cfm

Unit 6E.1



The Moon The main purpose of this section is to contrast the Moon with the Sun. Show a collection of photographs of US astronauts exploring the surface of the Moon. In particular, show some video clips of them walking on the Moon and driving the Moon buggy. Ask the class to write down in a table what the photographs tell us first about the main differences between the Sun and the Moon and then about any differences between the Earth and the Moon (such as the way the astronauts move, the colour of the sky, where the light comes from, what happens to dust raised). Discuss the differences between the Sun and the Moon with the class, noting particularly that the Moon is a cool place, and that light on it comes, like light on Earth, from the Sun.

Ask the class why they think we can see the Moon in the sky at night. Leave open for later why the Moon appears a different shape on different nights. We see the Moon by light from the Sun that is reflected to us by the Moon’s surface.

Ask advanced students for possible explanations of the differences they noted between the Earth and the Moon, particularly in the way the astronauts walked with springing steps, why they often fell over and why dust took a long time to settle even when there was no air to blow it around. (The force of gravity is studied in Unit 6P.1.)

Ask students what they think might have caused the surface features, such as craters, that can be seen on the Moon through binoculars and in photographs. Allow students to create similar features in the classroom by dropping a stone into fine sand or mud. This will lay the foundation for work in Grade 8 on planetary formation. You may wish to take it further here and link it to observations of ‘shooting stars’.

The NASA website, http://www.nasa.gov and their educational site http://www.thursdaysclassroom.com are useful resources for information about lunar exploration.

A class display of the Sun and the Moon

Create a display of photographs of the Sun and the Moon. Make very approximate scale models of the Sun, the Earth and the Moon from cardboard disks. Ask more advanced students to work out how far apart these will have to be placed to make a model of the Sun–Earth–Moon system on the same scale. The class should be clear about the relative magnitude of these distances, in particular the fact that the diameter of the Sun is about three times the distance from the Earth to the Moon.

A 1 : 109 scale will result in the Earth being about 1 cm in diameter, the Sun about 100 cm and the Moon about 3 mm On this scale the Sun–Earth distance will be about 150 m and the Earth–Moon distance is about 30 cm.



Day and night Challenge students, in groups, to design and make, from everyday materials, a model of the Sun–Earth–Moon system that can be used to demonstrate the movement of the Earth and Moon around the Sun. The Sun must be a light source. The objects need not be to scale. The system must show the spin of the Earth and the axis about which it is rotating. Ask them to indicate roughly the continents on the Earth and show where Qatar is.

Ask students to explain, using their models, the existence of day and night.

Mechanical models of the Sun–Earth–Moon system that can be used to demonstrate everything in this topic are commercially available but not necessary.

Seasons Ask students why they think it is hotter in summer than in winter. This will raise misconceptions, the most common of which is likely to be that they think the Sun is nearer to the Earth in summer. If they raise this, challenge them to explain the fact that in most of Africa, Australia and South America the hottest time of the year is December to February.

Ask students about the position of the Sun in the sky in summer compared with winter and then ask each group to show that using their model. Challenge them further to show how the Earth must move around the Sun during the year to create summer and winter. Ask them to explain why daylight time is longer in summer than in winter, and that near the poles in summer it is so long that there is no night.

Students will find the explanation of why it is hotter in summer rather difficult. Assist them using a torch that produces a clear long beam. Darken the classroom if possible. Shine the torch vertically downwards on a piece of paper and draw around the brightest spot. Shine it from the same height above the table at an angle of 40–50°. Draw around the spot again. Cut out the two pieces of paper and ask what the difference is. They will notice that they are a different shape and also that the one that is lit by the torch at 40–50° is larger. Discuss which was brightest and in which was the heat and light (this can be referred to as the Sun’s energy) more concentrated and less spread out? The same energy in summer is concentrated on a small part of the Earth and so it heats up more.

More advanced students may understand that another reason why the Sun’s rays are colder in winter is because they have to pass through more atmosphere, which absorbs more of their energy.

3 hours

The movement of the Earth Know that the Earth orbits the Sun once every year.

Understand why the Sun is higher in the sky during the summer than in the winter and why it is hotter in summer than in winter.

Make models from everyday materials to help explain scientific phenomena and technological solutions.

Galileo and Copernicus Encourage more advanced students to study the history of our understanding of the relative motion of the Earth and the Sun. Of particular interest is the difficulty experienced in the seventeenth century by Galileo in publishing his observations and conclusions that the Earth moved around the Sun when the conventional view (held as sacred by the powerful Catholic Church) at the time in southern Europe was the opposite. Copernicus, living in a different part of Europe did not face this opposition when he published the same conclusions.

Enquiry standard 7.2.3



Moon diary At least one month before this unit starts, ask students to keep a ‘Moon diary’ for a month. To do this, they need to go out at night to observe and draw the shape of the Moon in the night sky. Tell them to note: • the time of night they made the observation; • the approximate direction they were facing; • how high in the sky they were looking.

When the diaries are complete, ask students to describe in a few sentences in their books how the shape of the Moon changed during the month. Ask them if they can see a pattern in the changes and whether the pattern repeats itself, and, if it does, how long one cycle was.

Ask students about any other observations they may have made; for example, whether they ever saw the Moon during the daytime, or whether they saw, at the new Moon, the outline of the whole Moon as well as the bright crescent. Explanations for these can be left until later.

Ask students to make a flip book of the shape of the Moon, starting from the new Moon. Give them each a set of cards with identical feint drawings of a circle on them to ensure that they draw the Moon the same size and in the same place on each card.

Enquiry standard 6.2.3

Lesson plan 6.4 4 hours

The phases of the Moon and eclipses Know that the Moon revolves around the Earth once every 28 days and show how this causes the phases of the Moon.

Know that the gravitational attraction of the Moon and the Sun on the Earth’s seas causes the tides.

Know the causes of eclipses of the Sun and the Moon.

The phases of the Moon Challenge groups to use their Sun–Earth–Moon models to explain the different shapes of the Moon observed during the month. Help them to appreciate that what we see is the part of the Moon that is illuminated by the Sun. Help them to draw a diagram to show the relative positions of the Moon and Earth and the direction of the light from the Sun for the four quarters of the lunar cycle. Also ask them how long the Moon takes to complete one orbit of the Earth.

Explain that it is the gravitational attraction of the Moon on the water in the sea that causes the tides. A detailed explanation of this should not be attempted at this grade.

A useful gallery of Moon photographs in different phases can be found at the Maryland Science Centre observatory, http://www.mdsci.org/ exhibits/observatory/photo/index.cfm

Calendars Set more advanced students an exercise to compare the Saudi Islamic and Gregorian calendars,such as that set out in Lesson plan 6.4. This shows the Gregorian compromise made in the traditional length of the lunar month so that the calendar year has exactly twelve months.

Information on the World’s calendars can be found on http://webexhibits.org/calendars/index.html

Lesson plan 6.4

Eclipses Demonstrate using appropriate models, how eclipses of the Sun and the Moon occur. Ask students to draw diagrams showing both in their books. Show diagrams to explain how partial eclipses can occur. Note the time and date of the next eclipse of the Moon and, if possible, arrange for the class to observe it.

Show more advanced students how the shadows, such as that caused by the Earth in a lunar eclipse, consist of the umbra and penumbra. Tell them to note the difference between these when they observe the eclipse.

Show photographs from the Internet of a total solar eclipse and discuss an explanation for the bright light that can be seen around the outside of the Sun during the eclipse.

Details of many past and future eclipses can be found on the NASA eclipse webpage at http://SunEarth.gsfc.nasa.gov/eclipse/eclipse.html


Assessment


The Sun is bigger than the Moon, but they appear to be about the same size when you look at them from the Earth. Why is this?

TIMSS, Population 2

What causes day and night on Earth?

A. The Earth’s rotation on its axis.

B. The Earth’s revolution around the Sun.

C. The Sun’s revolution around Earth.

D. The Sun’s rotation on its axis.

A is correct

In regions near the North and South Poles, the Sun does not set for several months in the summer. Areas like these, such as the northern part of Norway, are called the ‘land of the midnight Sun’, because the Sun remains visible all the time and there is no night. Explain this.

Which of the following describes an eclipse of the Moon?

A. The Moon passes between the Earth and the Sun.

B. The Sun is not illuminating the side of the Moon facing the Earth.

C. The shadow of the Moon passes across the surface of the Earth.

D. The shadow of the Earth passes across the surface of the Moon.

D is correct

Draw a picture that shows what the Moon looks like when the Earth, Sun and Moon are arranged as shown in the diagram.


The diagram shows the Earth in two positions during its orbit around the Sun. Which position is summer in Qatar? Explain why it is hotter during the day in summer than in winter.

Unit 6E.1

273 | Qatar science scheme of work | Grade 6 | Unit 6P.1 | Physical processes 1 © Education Institute 2005

GRADE 6: Physical processes 1

Different kinds of forces

About this unit This unit is the first of three units on physical processes for Grade 6. It builds on work done on forces, static electricity and magnetism in Grade 5 and is linked to work in Unit 6E.1.





Previous learning To meet the expectations of this unit, students should already know what forces are and the effects they have on objects. They should have experienced how electrostatic and magnetic forces both attract and repel at a distance.

Expectations By the end of the unit, students know that there are two kinds of forces: contact forces and those that act at a distance. They recognise that all bodies exert gravitational attraction and that the Earth’s force of gravity on a mass of 1 kg is approximately 10 N towards the centre of the Earth. They distinguish between mass and weight. They know when to use bar charts and line graphs to express discontinuous and continuous data and interpret such graphs, including calculating and interpreting the gradient of a straight line.

Students who progress further measure the magnitude of several different kinds of non-contact forces. They form an intuitive concept of density and recognise that floating and sinking depends on density and that the upthrust on a floating body is equal to its weight.

Resources The main resources needed for this unit are: • paper clips, cotton, string, scissors, re-usable adhesive • forcemeters of various sizes • simple magnetic and electrostatic equipment • balance and/or a set of masses 100 g to 1 kg • bathroom scales calibrated in kilograms • buckets, variety of floating and sinking objects, balloons • fresh eggs, salt

Key vocabulary and technical terms Students should understand, use and spell correctly: • force, newton, forcemeter • magnetic force, electrostatic force, gravitational force • tension • mass, weight, weightlessness, • upthrust, float, sink • gradient, proportionality

UNIT 6P.1 8 hours





5.13.5 Know that magnets attract objects that contain iron, but not those that contain other metals such as aluminium or copper.

6.14.1 Distinguish between forces that act at a distance (such as gravity, magnetism and electrostatic force) and contact forces.

5.13.1 Know that electrostatic charge is generated by friction when an insulator is rubbed and that two kinds of charge can be created in this way.

6.14.2 Know that all bodies exert a gravitational attraction which is stronger close to the body than further away and that the force of gravity on the surface of the Earth on a mass of 1 kg is approximately 10 N.

3 hours

Contact and non-contact forces

5 hours

Gravity and weight

6.14.3 Distinguish between mass and weight. 7.17.4 Know that the weight of an object is less in water because of the upthrust of the water acting on it.

6.2.2 Know when to use bar charts and when to use line graphs to represent discontinuous and continuous data and be able to interpret such graphs.

Unit 6P.1


Activities


Introduction Recall earlier work on forces. Ensure students know that forces are pushes and pulls and are measured in newtons. Ask them to estimate the size of a number of forces (e.g. the forces involved in picking up a book or opening a door) and check their estimates.

Make sure students are familiar with the concept of tension in a string as a force. Tie a string to a forcemeter and ask one student to pull gently on the string and a second to hold the meter. Cut the string to show that the meter reads zero when the tension is removed.

Perform the following demonstration, which demands explanations and shows the similarities between contact forces and distance forces. Tie a piece of cotton about 10 cm long to a paper clip. Stick the other end of the cotton to the desk with a piece of re-usable adhesive. Clamp a magnet (strong) above the clip about 12 cm from the desk so that the clip appears suspended in the air under the magnet, tethered to the desk by the cotton and re-usable adhesive. Ask the class to explain the position of the paper clip.

Ask the class what will happen if the cotton is cut with scissors. Cut the cotton to test their prediction; the paper clip is attracted to the magnet. Ask the class what will happen if you now cut between the paper clip and the magnet. Do so (using steel scissors); the clip falls to the bench.

Ask for explanations. Guide the discussion towards the differences and similarities between the non-contact force due to the magnet and the contact force of the tension in the string. Both act on the suspended clip and, when either is stopped, the clip will move. Mention also the non-contact force of gravity which causes the movement when the magnetic force is removed.

This demonstration requires practice. The optimum length of cotton will depend on the strength of the magnet.

It is essential that the scissors are made of steel and are large, so that they block the magnetic field.


3 hours

Contact and non-contact forces Distinguish between forces that act at a distance (such as gravity, magnetism and electrostatic force) and contact forces.

Recall work on magnetism Recall work from Grade 5 on magnetism. Allow groups to repeat some of the activities, particularly those involving suspended magnets, to ensure they are familiar with both attraction and repulsion. Recall the concept of the magnetic field as the mechanism through which the force acts. In addition, show that a magnetic field is blocked by a sheet of steel to confirm the explanation of the observation in the introduction.

Recall work on electrostatics Recall work from Grade 5 on electrostatics. Repeat some of the simple activities that show both repulsion and attraction from a distance

Unit 6P.1



Recall work on contact forces Ask students to make a list of the different kinds of contact forces they have come across. They will readily identify pushes and pulls of different kinds and will recall friction. Remind them of the force that can be exerted by something under tension, such as a coiled spring or a stretched rubber band.

Check students’ understanding of contact forces by asking groups to repeat some of the activities in Units 5P.2 and 5P.3 or carry out new ones, such as making a model arm out of cardboard or pieces of wood or plastic with two rubber bands to serve as muscles. This should show how the two muscles exert forces that oppose each other. Ask students to feel their muscles tightening and stretching as they move their forearm.

Enquiry skill 6.3.1

Summary: classify different forces Provide the class with a list of examples of forces in everyday life and ask them (for homework) to classify them as contact or non-contact forces.

The non-contact force of gravity may be mentioned at this stage and included in the list, or it may be left until the next section.

Introduction Discuss why objects always fall downwards. Discuss why a force must be exerted to throw a ball upwards and why eventually it will come back down. Hang an object on a string and cut the string; remind the class of the similarity between this and the first demonstration in which the paper clip was attracted to a magnet.

Explain how Newton was the first person to propose that objects attracted each other. Explain that this force of attraction depends on the mass of the object and that it is very small unless the object is very large, like the Earth. They should understand that when a ball falls to Earth, the Earth also moves upwards towards the ball, but the movement is so small we cannot detect it.

More advanced students may ask how we know that the Earth moves upwards towards a falling ball if the movement is too small to detect. This could lead to a discussion of scientific theories and how Newton’s theory replaced the old Greek theory because it could explain things that the Greek theory could not, such the revolution of the Moon around the Earth.

Enquiry skill 7.2.1

5 hours

Gravity and weight Know that all bodies exert a gravitational attraction which is stronger close to the body than further away and that the force of gravity on the surface of the Earth on a mass of 1 kg is approximately 10 N.

Distinguish between mass and weight.

Know when to use bar charts and when to use line graphs to represent discontinuous and continuous data and be able to interpret such graphs.

The force of gravitational attraction depends on the mass of the objects This activity investigates the force of gravitational attraction between the Earth and objects of different mass. Remind the class of Newton’s idea that the force that attracts the Earth and an object depends on the mass of both of them. Explain that in this activity they will measure the force between the two bodies and will assume that the mass of the Earth is constant

Students should work in groups. Provide each group with a balance and a variety of objects whose masses are between roughly 100 g and 1 kg and ask them to determine the masses of the objects. Alternatively, provide students with a collection of masses. Ask students to find the force of gravity acting on the objects in newtons using a forcemeter. Discuss the kind of graph required to represent these data. Tell students to plot a line graph showing the relationship between the mass and the force of gravity (with the independent variable, mass, on the x-axis). Interpret the straight-line graph, introducing the concept of proportionality in a simple manner by asking questions such as ‘what happens to the force of gravity when the mass doubles?’

The use of the investigation planning poster will help students realise that the mass of the Earth is a variable in this activity but that it is being held constant. It will also help to distinguish the dependent variable (gravitational attraction between the object and the Earth) and the independent variable (mass of the object).



Ask more advanced students to calculate the gradient of the graph, which will represent the force of gravity exerted between the Earth and a mass of 1 kg.

Mass, weight and weightlessness The previous experiment has shown that the two concepts of mass and weight are different and are measured using different units.

Reinforce this idea by showing videos of scientists working in the International Space Station (ISS), where the force of gravity on objects is effectively zero and objects do not fall but float. Try to find clips that show the scientists moving and also other smaller objects being made to move; students may note that objects with a small mass can be made to move with a smaller push than objects with a large mass.

Develop this intuitive concept of mass further by hanging a range of objects of different masses from strings or ropes and asking students to find out how easy it is to make the objects move.

Conclude that mass and weight are different concepts and define them for the class.

Show video clips of astronauts walking (in heavy space suits) on the Moon. Note that they take long bouncing steps (as though they are on a trampoline) and often fall over. When they fall, note that they fall slowly and do not appear to hurt themselves or damage their suits. Challenge students to explain these observations. The reason is the low gravitational attraction between them and the Moon – it is one-sixth that on Earth.

Ask students to weigh themselves and then find an object that weighs on Earth as much as they would weigh on the Moon (this could be a homework task).

Ask students to make a table showing their own mass and weight on Earth, in the ISS and on the Moon.

Encourage more advanced students to do further calculations of the weight of objects in different gravitational environments.

ICT opportunity: Download video clips showing scientists working under weightless conditions and astronauts moving on the Moon.

The masses of the hanging objects should range from very light (a piece of popcorn hanging on cotton) to quite large (a house brick hanging from suitable rope).

It is not desirable to use the word inertia at this stage.

Floating eggs This challenging demonstration can be done before of after the next section. Ask for an explanation at the end of the unit.

Place an egg (fresh and uncooked) in a jar of water and note that it sinks.

Place another in a jar of salt water and note that it floats.

Half fill a jar with water. Pour in, very slowly, some salt water down a tube to the bottom of the jar until the jar is nearly full. Place a third egg in the jar very carefully and note where it floats.

Try this beforehand to get the right concentration of salt water.

The third jar must contain two layers of water, fresh water on the top of salt water. The salt water can be put in first and the fresh water added carefully on top (by pouring, for example, down the back of a spoon). The egg will float in the salty layer.



Changes in weight Ask students whether they can think of conditions on Earth when their weight changes. They may think of the feeling of lightness when they descend in a lift or they may realise that they are weightless when they are floating in water.

Both these effects can be investigated. Suggest that (as homework with their parents) they try standing on bathroom scales in a lift. The effect of water on weight can be investigated by students working in groups in the classroom.

Provide each group with a bucket of water and an inflated balloon. Challenge them to push it under the water. Introduce the idea of upthrust in the water as an upwards force that opposes the weight of the object placed in water.

Provide each group with a set of objects and ask them to classify them according to whether they become weightless when they are placed in water; whether they float like the objects in the ISS. Ask them to tabulate their observations and draw some simple conclusions about what kinds of objects float and what sink. Students will use terms such as ‘heavy’ and ‘light’; more advanced students will realise that these are not the correct terms. Introduce the terms dense, less dense and more dense.

Provide more advanced groups with a bucket of water and a variety of objects that can be suspended from a forcemeter. Ask them to measure the weight of the object in and out of the water and tabulate the results. Ask them to calculate the upthrust on each object and write it in the table. Challenge them to draw a conclusion about the relationship between upthrust and weight (out of water) of floating objects.

Tell them to repeat the activity, using the same objects, with seawater or salt water. Ask them to note the difference in results.

Suggest to more advanced students that they draw lines on the objects to see how deeply they float in the two water samples. Introduce the concept of density as mass per unit volume to them at this stage

The objects must include some that float and some that sink.

Make the salt water as concentrated as possible to observe the difference most clearly.

Summary: a weight slideshow Ask groups of students to make a display or a slideshow showing how weight changes in different conditions. This should be a summary of the work done in the unit. Encourage them to illustrate the display using pictures from the Internet. Alternatively, ask students to contribute materials to a class display.

ICT opportunity: Use of the internet.


Assessment

Possible assessment activities Notes School resources

Haya drew a picture of herself (right) standing at four different positions on the Earth. Draw an arrow at each of the four positions to show the direction of the force of gravity on Haya.

The drawing at position A shows Haya holding a ball on a string. Draw the ball and string in positions B, C and D.

QCA Key Stage 3, 2003, level 4 (part question)

Ibrahim hung a magnet from the bottom of a spring. The spring stretched. What was the force that caused the spring to stretch?

Then Ibrahim held another magnet near the first one as shown. What happened to the spring as he did this? There are now two forces acting on the upper magnet. Name them and draw their directions in the diagram. For each force, state whether it is a contact or a non-contact force.

What will happen to the first magnet when Ibrahim removes the second magnet?

A camera has a mass of 0.6 kg. What is its weight? It is placed on a spacecraft which takes it to the Moon. What is its mass and its weight (a) at the point of zero gravity on the journey and (b) on the surface of the Moon? (The gravitational attraction caused by the Moon is one-sixth that caused by the Earth.)

Imagine that you live on a planet where the force of gravity is only half that on Earth. You visit Earth. Make a diary of some of the things that you did when you stepped out of your spacecraft and how difficult they were to do.


How would you investigate how the force caused by one magnet on another changes when the two magnets are moved away from each other. Carry out the investigation and display your results graphically.

Enquiry skills 6.1.3 and 6.2.2

An investigation planning poster will help to design this.

Unit 6P.1



Light

About this unit This unit is the second of three units on physical processes for Grade 6.





Previous learning To meet the expectations of this unit, students should be aware of the different sources of light in our lives and also how light sources can form shadows.

Expectations By the end of the unit, students know that light travels very fast in straight lines. They know that we see illuminated bodies by reflected light and that shiny objects reflect light better than dull objects. They recall that objects placed in front of a light source create shadows and know that white light is composed of light of different colours.

Students who progress further recognise that light is a form of energy that can be made from, and converted into, other forms of energy. They recognise that many mirrors are curved and that these are often used for concentrating light into a beam.

Resources The main resources needed for this unit are: • light meter • torch, laser pointer • cardboard box • small mirrors, re-usable adhesive • collection of materials with different surfaces, ranging from reflective to

dull • toothpicks, white card, coloured pens

Key vocabulary and technical terms Students should understand, use and spell correctly: • light source, beam of light, illuminated object, brightness • mirror, reflection • laser • shadow clock, sundial, gnomon • colour spectrum

UNIT 6P.2 11 hours





6.13.1 Know that the Sun and stars are light sources and that the Sun is the source of our daylight.

6.16.1 Know that light moves in straight lines and, in consequence, objects placed in front of a light source create shadows.

3.11.2 Recognise that the shape of a shadow is similar to the shape of the object that makes it.

6.16.2 Know that light has a velocity that is very high.

3.11.3 Show that light can pass through a transparent object but not through an opaque one.

6.16.3 Know that we see light sources because light travels from them to our eyes and that we see objects that are not light sources because they are illuminated by light sources and light is reflected into our eyes.

8.18.2 Know that the intensity of light can vary depending on the light source and its distance away; measure the intensity using a light sensor.

3.11.5 Know that light can be reflected by mirrors.

6.16.4 Know that objects can absorb or reflect the light that shines on them, that shiny objects reflect light better than dull objects and that dark objects reflect less light than light-coloured objects.

8.18.4 Describe how light is reflected at a surface and understand the difference between reflection by rough and smooth surfaces. Know the characteristics of an image formed in a plane mirror. Describe everyday applications of reflection.

4 hours

What is light?

2 hours

Shadows

3 hours

Reflection

2 hours

The colours of the rainbow

6.16.6 Know that coloured objects reflect only their colour and absorb other colours when illuminated in white light.

6.16.5 Know that white light is composed of light of different colours.

8.18.6 Demonstrate how white light can be split into coloured light by refraction and explain examples of dispersion in everyday life (e.g. oil on water, rainbows).

Unit 6P.2


Activities


Where does light come from? Recall earlier work on light by asking students whether a number of bright objects are light sources or not. Examples of bright objects are a car headlight, a mirror, a sheet of foil, a candle, the Sun, the Moon, a star.

Ensure that everyone is clear about the difference between objects that are bright because they give off light and those that are bright because they reflect light that is created by other sources. Some students may have difficulties in realising that the Moon differs from the Sun and stars in this respect.


Estimating and measuring light brightness Ask students to think about how bright different places in and around the classroom are. Ask them to predict an order of brightness for the places and write down their prediction. Then ask them to go and look at the different places and test their prediction using just their eyes. They should now write a new list of the places in order of brightness. Finally, let them use a light meter to test the amount of light in the different places. Now ask them to write a third list according to the results given by the light meter.

Introduce more advanced students to the concept of light energy: the brighter the light, the more light energy it contains. The more light energy falls on the meter, the further the meter needle is deflected.

Suitable places might be near a window, near a light, on the desk, under the desk, in a cupboard, in the corridor.

Enquiry skill 6.1.1

4 hours

What is light? Know that we see light sources because light travels from them to our eyes and that we see objects that are not light sources because they are illuminated by light sources and light is reflected into our eyes.

Know that light moves in straight lines and, in consequence, objects placed in front of a light source create shadows.

Know that light has a velocity that is very high.

Can we see a beam of light? Pose a question to the class: ‘Can we see a beam of light?’ They will agree that we can see a beam of light if it enters our eyes, but ask them if we can see one that does not enter our eyes. Show them a small box with a hole at either end and shine a torch through the holes. The torch beam can be detected on a sheet of paper after it has left the box. Make another hole in the top of the box and ask the students what they think they would see if they looked into the hole at the top when the torch is shining through the box. Make a note on the board or OHP of how many predict that they would see light and how many predict that they would see nothing.

Let everyone look into the box to convince themselves that the light beam cannot be seen.

Demonstrate the laser to the class. Shine it through a glass of water and note that the beam can be detected after it has emerged from the water. Ask if the beam can be seen going through the water (darken the room if possible). Add a few drops of milk to the water and look again at the beam. The milk makes the beam visible. Ask for explanations. This observation will be discussed further in the next topic.

Safety: Do not allow students to handle lasers. Take care not to shine it in eyes

Unit 6P.2



Light travels in straight lines Challenge the class, working in groups, to provide convincing evidence that light travels in straight lines. They will find it difficult and may need appropriate help. Direct them to the phenomenon of shadow formation, which can only be explained satisfactorily by assuming that light travels in straight lines. Encourage groups to use a torch to make shadows of a regular object, such as a matchbox. Draw attention to the edges of the shadow, which are straight. The straight edges can be extrapolated back to the torch bulb.

Make a small hole at the centre of each of three pieces of card. Arrange the cards so that they are upright a short distance from one another and demonstrate the passage of a beam of light from a torch through the three holes. Point out that the beam can only emerge from the final hole if all three holes are lined up in a straight line.

Enquiry skill 6.1.2

How fast does light travel? Challenge the class to think up an activity that would give them some idea of the speed of light. To start them thinking, ask them how they might try to find out how long it would take for a ball to get from the penalty spot to the goal. Then ask them how they would do the same with a pulse of light from a torch. In the first case, someone could clap when the ball was kicked and someone else could clap when it reached the goal. Get them to experiment with a similar idea using light from a torch or a laser.

When they try to apply any such experiment to light they will realise that it travels so fast that there appears to be no time between its leaving the start and arriving at its destination. Draw the conclusion with them that the speed of light is too fast for them to measure.

Give students the speed of light – 300 000 km per second. This is an unimaginably large number; to make it more comprehensible, explain that it means that it takes just over a second for a pulse of their torchlight to travel to the Moon and about 8 minutes for it to get to the Sun.

2 hours

Shadows Know that light moves in straight lines and, in consequence, objects placed in front of a light source create shadows.

Forming shadows Recall (or repeat if necessary) earlier work on the formation of shadows by the Sun and how they change during the day. Elicit from students the two observations that the shadow changes in both length and direction. Ask them to explain this.

Provide students, in groups, with some sheets of card or paper, a pair of scissors and a torch. Ask them to cut the paper into an interesting shape and then to predict what the shadow of the shape will look like when they shine a torch at the shape. Darken the room and ask them to test their predictions. Then ask them to predict what will happen to the shape and direction of the shadow as the torch is moved. Again ask them to test their predictions.

This activity is intended to help you find out what students know and understand about light and shadows. Follow it by challenging them to design and make a shadow clock out of a piece of wood and some card as a base. Ask them to think about what they must do to plan this activity and how they are going first to calibrate and secondly to test their product. Students can work as a group or as individuals in this activity.

Show students some pictorial examples of shadow clocks and make display of the pictures. Introduce the words sundial and gnomon.

This activity requires a darkened room.



Using a mirror Give each group a mirror and set them several tasks, for example: • Ask them to place it vertically on a sheet of paper and show, using a torch, how a beam of

light is reflected by it. • Ask them to use it to see behind them and then draw in their books a diagram to represent

the direction of the light beam from an object behind them to their eye. Give assistance by showing how to represent light beams by straight lines with arrows

Place the laser in one place (such that it cannot shine in anyone’s eyes). Note where the beam strikes the wall and stick a mirror to that spot on the wall using re-usable adhesive such as Prestik®. Note where the reflected beam now strikes the wall and repeat using a second mirror. Repeat the activity as many times as possible using additional mirrors. Discuss the difference between a torch beam and a laser beam and why this activity could not be done with a torch.

Ask students to use their own knowledge and secondary sources to identify everyday uses of mirrors. Ask them to list these uses in their books. Discuss what they have found out with the whole class and list uses they mention on the board or OHP.

Encourage more advanced students to explore, in the discussion, why certain mirrors are curved.

Safety: Ensure that the mirrors used do not have sharp edges.

3 hours

Reflection Know that objects can absorb or reflect the light that shines on them, that shiny objects reflect light better than dull objects and that dark objects reflect less light than light-coloured objects.

Reflection of light by different surfaces As a starter, shine a laser light at a mirror and then at the wall near the mirror and ask students to look at the dot of light made by it. Challenge them to explain the difference but do not provide the answer at this stage. Tell them that you will ask them again at the end of this topic.

Organise students into groups to carry out an activity to find out and record how different surfaces reflect light and to draw conclusions from the observations. Provide groups with a collection of shiny and dull surfaces (e.g. mirrors, polished metals, clear rigid plastic, paper, gloss and matt painted surfaces, polished wood, paper, card). Ask groups to find out which surfaces they can see themselves in and which ones reflect a torch beam. Ask them to record their results in a table and to draw conclusions from them.

Ask the class why we can see objects in daylight but not in the dark. Draw from the questions and answers that we see objects because light from a source (such as the Sun) is reflected off the object towards our eyes. Show this by drawing a diagram on the board or OHP. Return to the starter question (show it again). Note that, when a laser shines into a mirror, most of the light is reflected one way only and very little goes towards our eyes. When the light hits the wall, it is reflected in all directions so that we can all see it, no matter where we are sitting looking at it. Show this difference between a reflective surface and a matt surface in two diagrams on the board or OHP.



Producing a spectrum Demonstrate a spectrum in a suitable place in the school by reflecting sunlight from a mirror placed in a trough of water to create a water prism. Reflect the spectrum onto a ceiling.

Talk about the colours of the spectrum and where students have seen the colours before. Ask them to draw the spectrum, in the correct order of colours, in their books and to label the different colours. Show other examples, such as reflection of light from a CD.

Discuss with the class where they think the colours have come from. List their conclusions and discuss how they might test their ideas. The two likely conclusions are that the colours come from the light or that they come from the water.

Enquiry skill 6.1.2

2 hours

The colours of the rainbow Know that white light is composed of light of different colours.

Making white light from coloured light Show the class how to make a spinner coloured with all the colours of the rainbow. Allow students to make them individually and try them out. They will see that as the card spins, and the colours appear to merge, the overall colour will appear to be white (or near white).

Discuss the results of both the activities involving colour. Draw from them that the only explanation for the observations is that white light is made up of coloured light and that mixtures of coloured light can be combined to form white light.

Students will need: white card, toothpicks and coloured pens.


Assessment


Classify the following according to whether they are illuminated objects or sources of light.

The Sun, the Moon, the star Betelgeuse, the planet Jupiter, a laser, a mirror, a light bulb.

The top diagram shows a light bulb X, a piece of card and a white screen. Two light rays have been drawn from the bulb to the screen. Five points, A, B, C, D and E, have been labelled on the screen. Give the letter of one point which is in shadow.

Bulb Y is added. The bottom diagram shows two light rays from each bulb. Look at the bottom diagram. Which point on the screen will be in the darkest shadow? Give the letter.

Give the letter of one point on the screen which will be lit up by both bulbs.

Give the letter of a point on the screen will be lit up by bulb X only?

QCA Key Stage 3, 1999, level 4

Tarik dazzles his friend at the other side of the classroom by reflecting sunlight from his watch. Tarik’s arm is lit up by the Sun. Explain why everyone can see his arm but only his friend is dazzled by his watch.

Explain why we cannot see around corners.


Explain why we can see objects during the day but we cannot see the same objects when it is dark.

Unit 6P.2



The effects of forces

About this unit This unit is the third of three units on physical processes for Grade 3 and the second of two on forces. It builds on work begun in Unit 6P.1.





Previous learning To meet the expectations of this unit, students should already be able to recognise a force and to explain, in simple terms, what it is. The will have experienced non-contact forces such as magnetic forces and contact forces such as friction. They should know that all bodies exert gravitational attraction and that the Earth’s force of gravity on a mass of 1 kg is approximately 10 N towards the centre of the Earth. They should be able to distinguish between mass and weight.

Expectations By the end of the unit, students know that there is often more than one force acting on a body and that when forces on a moving object are unbalanced, the object will speed up or slow down. They recall that air and water resistance are forms of friction and know that the terminal velocity of a falling body is reached when the forces on it are balanced. They represent the forces acting on a body with arrows that point in the direction of the force.

Students who progress further represent the magnitude of a force by the length of the arrow and calculate the magnitude of resultant forces in linear cases. They realise that a resultant force can cause acceleration or deceleration of a moving body and that a force acting on a body at right angles to its direction of movement does not affect its velocity in that direction. They realise that terminal velocity is determined not only by the weight and shape of a falling body but also by the viscosity of the medium.

Resources The main resources needed for this unit are: • forcemeters, string, objects to pull (e.g. 1 kg mass or 1 kg sandbag) • stopwatches, objects for dropping • glass sheet (smooth edges) • investigation design poster • glycerine (glycerol), methylated spirits, paraffin, medicinal paraffin,

cooking oil • tall plastic bottles or large measuring cylinders • ball-bearings of different sizes, small magnet on a string • scrap A4 paper, paper clips • Internet access.

Key vocabulary and technical terms Students should understand, use and spell correctly: • force, weight, tension, friction, resultant • velocity, acceleration, deceleration • viscosity, resistance, terminal velocity

UNIT 6P.3 6 hours





5.12.1 Know that forces are pushes and pulls, and that the unit of force is the newton.

6.15.1 Know that a force on a stationary object can cause it to move or to change shape and that a force on a moving object can cause it to change direction, or speed.

7.16.2 Give and explain everyday examples of how forces can cause stationary objects to move and can change the direction and speed of an object that is already moving.

6.15.2 Realise that there is often more than one force acting on a body and that these are balanced if the body is stationary.

6.15.3 Know that an object at rest on the ground has two equal and opposite forces acting on it.

6.15.4 Know that when forces on an object are unbalanced, there is a resultant force on it that can cause it to change its shape, speed or direction.

7.16.6 Recognise that there may be many forces acting on an object that may not be in balance, and be able to represent them in diagrams and to make deductions about the size and direction of any resultant forces.

5.12.4 Know that water and air resistance slow an object down when it moves through water or air and that the shape of an object affects the size of this resistance.

6.15.5 Know that air resistance and water resistance are forms of friction that affect the speed of objects moving through the air or the water, and know that the terminal velocity of a falling body is reached when the forces acting on it are balanced.

2 hours

What forces can do

4 hours

Air and water resistance

6.15.6 Represent the forces acting on a body with arrows that point in the direction of the force.

7.16.5 Represent the forces acting on an object diagrammatically, using arrows that show direction and magnitude.

Unit 6P.3


Activities


Introduction Recall earlier work on forces. Make sure students know that forces are pushes and pulls and are measured in newtons. Ask them to construct a concept diagram around the word force. They will need help to start this process. After a few minutes, summarise what they have developed in a class concept diagram either on the board or, better, on a computer or an OHT so that you can keep the result until the end of the unit when the exercise can be repeated.

The process will probably generate misconceptions, which should be addressed.

If necessary, repeat some of the activities from Unit 6P.1 or earlier grades as demonstrations.


Balanced forces Recall and develop further the ideas of balanced forces in Unit 6P.1. Ask whether there is any force acting on the book you place on the desk. It is not immediately obvious that there is, but some students might give the correct answer. To consolidate, hang the book (or any object) on a string (refer back to Unit 6P.1) and note that it is stationary. Ask what happens if the string is cut. Does gravity suddenly start to act when the string is cut or is it there all the time? Draw the object on the board or OHP; show its weight – gravity acting on it – and ask what other force must there be to stop it moving downwards.

Ask someone to draw the forces acting on the book on the desk. Label them both.

Friction Students should have studied friction In Grade 5 and it should have appeared in the concept diagram. Repeat a simple activity dragging a mass over several different surfaces (e.g. glass, bench top, carpet).

Use this activity to show how we can represent forces by arrows showing the direction of the force. In this case the two arrows are the pulling force exerted by the student and the frictional force.

This can be taken further, but less advanced students will find these ideas difficult. Ask them if they think that the two forces are balanced. They are only balanced if the object is moving with a constant velocity. If it is speeding up, the pull is greater than the friction; if it is slowing down, the friction is greater than the pull. Show these scenarios by changing the size of the arrows. Introduce the concept of the resultant force.

Less advanced students should be able to recognise that, in order to start the block moving, the pull must be greater than the friction, but they may have difficulty with the idea that the pull will be equal to the friction if the object moves with a constant velocity.

2 hours

What forces can do Know that a force on a stationary object can cause it to move or to change shape and that a force on a moving object can cause it to change direction, or speed.

Realise that there is often more than one force acting on a body and that these are balanced if the body is stationary.

Know that when forces on an object are unbalanced, there is a resultant force on it that can cause it to change its shape, speed or direction.

Represent the forces acting on a body with arrows that point in the direction of the force.

Give the class a small written exercise (give it individually but allow group discussion) showing diagrams of bodies with forces acting on them. Ask students to draw and label the forces and, by the size of the arrows, give some idea of the relative size of the forces. Possible examples include: a boy on a skateboard; a moving car; an aeroplane flying; a lift cage; a football in the air; a boat. Some harder ones may be added, such as a skateboarder going downhill.

Unit 6P.3


Objectives Possible teaching activities Notes School resources Several important ideas must emerge from the discussion of these examples (most have been

discussed before and so will be revisited here): • More than two forces may be acting on the body (e.g. friction, the pull of the engine and air

resistance in the case of the car). • For a moving object, if the velocity is constant, the forces making it move are exactly

balanced by the forces opposing movement. • For an accelerating or decelerating object, the forces making it move and the forces opposing

movement are not in balance. • There may be forces acting on the body that have no effect on its movement (such as the

weight of a car moving horizontally) because they act at right angles to the direction of movement. Pay particular attention to the example of the aeroplane with four forces (thrust, air resistance, weight, lift) acting on it. Ask what might happen when any two opposing ones become unbalanced.

Galileo’s experiment on falling bodies There always has been, and still is, disagreement among the public over whether heavier bodies fall faster then lighter ones. Ask the class for their views. Tell them (or show a video) about Galileo’s often quoted experiment in which he dropped two different canon balls simultaneously off the top of the Leaning Tower of Pisa. Galileo’s prediction was that they should both fall with the same velocity.

Ask students, in groups, to design and carry out an investigation to test Galileo’s prediction. They may need assistance with the design work – the investigation planning poster will help. You may choose, in this case, to go though the design thinking as a class exercise and just leave groups to execute it.

Students should have two objects of differing mass but high density to drop. This will minimise the effect of air resistance, Two different sized ball-bearings are ideal but they should not be too small. Find a suitable place where students can drop the objects safely, such as a stairwell or a first-floor window.

Students may find a detectable difference in the dropping times. If they do, leave any explanation until after the next section and then ask them to explain it.

To add context, ask students to find out what they can about Galileo and this experiment. Much is available on the Internet. A small display could be created either by them or by you.

A video or a software presentation may be available on Galileo’ famous experiment on falling bodies.

Many pictures of the Leaning Tower of Pisa can be obtained from the Internet.

Enquiry skills 6.1.2, 6.2.4 Safety: Supervise students appropriately when they drop hard objects from a window or stairwell to ensure they do not hurt anyone or cause any damage.

ICT opportunity: Use of the Internet.

4 hours

Air and water resistance Know that when forces on an object are unbalanced, there is a resultant force on it that can cause it to change its shape, speed or direction.

Know that air resistance and water resistance are forms of friction that affect the speed of objects moving through the air or the water, and know that the terminal velocity of a falling body is reached when the forces acting on it are balanced.

Represent the forces acting on a body with arrows that point in the direction of the force. Air resistance

Students may have met the idea of air resistance when they first studied friction in Grade 5. Ask them to recall what they learnt then. Build on it with following activity.

Challenge students, working in groups, to make a particular object fall as fast as possible and also as slow as possible under standard conditions. The object might be a half sheet of A4 paper with a paper clip attached. The use of the planning poster may help groups to control variables. Some students may need help with using stopwatches.

This investigation offers an opportunity to consider how accuracy might be improved by repeating the experiment several times and taking an average result for the time of the drop.

Enquiry skills 6.1.1, 6.1.3, 6.3.3, 6.2.4

Mathematics: A knowledge of working out averages is desirable.

For more ideas see Lesson Plan 3 for Grade 5



Discuss the results as a class, including the work on Galileo’s experiment. Students will probably suggest air resistance as the reason why some objects drop more slowly than others. They should also come to the conclusion that, in the absence of air resistance, all objects fall at the same speed. These conclusions should be summarised on the board or OHP.

More difficult is the concept of a terminal velocity. You could introduce this idea here or you may prefer to leave it until after the next investigation.

Finally, ask the class if they have ever seen any ‘shooting stars’. Explain that these are not actually stars but pieces of dust falling through the upper atmosphere. Ask them why these glow brightly and appear to burn up. Some may recall that friction generates heat; if no one mentions this, ask them to rub their hands together. Shooting stars generate so much heat because of air resistance – friction between the dust and the air – that they burn up. Discuss the 2003 Space Shuttle disaster and why it is important for spacecraft that re-enter the atmosphere to be coated with heat-resistant tiles.

Air and water resistance Recall work done in Grade 5 in which students dropped objects that had different shapes but the same mass through water. If necessary, ask them to repeat this investigation (Unit 5P.3).

Extend this by giving each group a small ball-bearing and asking them to find out how long it takes to drop through tall containers (large measuring cylinder or large plastic bottle) filled with different liquids. To save time, and to reduce the use of liquids, ask each group to use a different liquid.

The groups will have to make a decision about controlling the height the ball drops. They should also consider how to improve accuracy by repetition.

Tabulate all the groups’ results and discuss them as a class. Ask students why they think the time for the ball to drop differs from liquid to liquid. They will observe that some liquids appear to be ‘thicker’ than others and the ball slows up more in those. You can introduce the concept of viscosity in a qualitative way; the most viscous liquid being the one that offers the most resistance to the movement.

Ask them to describe the change in velocity of the falling objects in this investigation and in the last one in air. Draw from them the observation that the object speeded up from zero initially but, gradually, it stopped speeding up until it seemed to be falling at a constant velocity. Tell them that this constant velocity is called the terminal velocity and that the terminal velocity will depend on the resistance of the medium through which the ball falls and also on the weight of the ball. Ask students to think back to Grade 5 work and recall that shape is also important in determining air or water resistance.

Getting the ball-bearing out of the bottle after the experiment can be a problem – a small magnet on a string is useful.

Suitable liquids include water, glycerine (glycerol), methylated spirits, paraffin, medicinal paraffin, cooking oil.


Assessment


The lift shown in the diagram is in a tall building and hangs from a strong cable. The movement of the lift is affected by only two forces. These forces are the tension in the cable and the weight of the lift.

Which of the following list is correct (a) when the lift is not moving, (b) when the lift is moving upwards and its speed is increasing and (c) when the lift is near the top of the building and is moving upwards but slowing down?

A. The tension is greater than the weight.

B. The tension is equal to the weight.

C. The tension is less than the weight.

Adapted from QCA Key Stage 3, 1996, level 6

Which of the following are forces?

A. The movement of a boy on a skateboard.

B. The push of the air coming from a jet engine.

C. The weight of a girl.

D. The pull of a car on a trailer.

E. A ball falling through the air.

F. Water coming out of a tap.

The diagram shows a trailer that can be pulled by a car.

a. The car exerts a force A on the trailer. What is force B and how is it caused?

b. There is another force acting on the trailer. Draw it and label it C. What effect does it have on the movement of the trolley?

c. How do A and B compare when the trailer is (i) accelerating, (ii) moving with a constant velocity, (iii) stationary?


The diagram shows a seed.

a. Why is the parachute at the top of the seed useful to the plant?

b. What is the effect of the parachute on the terminal velocity of the seed?

c. Describe how you would investigate the effect of the parachute on the terminal velocity of the seed.

d. If the weight of the seed is 0.02 N, what is the size of the upwards force acting on the seed when it is falling at its terminal velocity? What is this force called?

Unit 6P.3

science units grade 6 · 6l.2 harmful micro-organisms 217 6m.2making pure substances from mixtures...

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