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COLLINS KEY STAGE 3 SCIENCE WORKBOOK 3 ANSWERS

DRUGS AND BEHAVIOUR

WHAT IS A DRUG?1

Legal drugs Illegal drugs

caffeineaspirinalcohol

heroinmarijuanacocaine

2 a) An addict needs a constant supply of a drug like heroin just to cope with life.b) Withdrawal symptoms are the symptoms that occur when an addict stops taking drugs suddenly.

3 There are four main groups of drugs: stimulants, depressants, painkillers and hallucino-gens. Stimulants speed you up and give you energy. Depressants calm you down. Painkillers are useful drugs that can make life much better for people in constant pain. Mor-phine, which is the basis for heroin, was used as a powerful painkiller before people realised how addictive it was. Hallucinogens can make you see things that are not there.

4 a) While they have been taking the drug, their body has become used to it. If they have been off drugs for a while and then they take their normal dose, the body may not be able to cope and death can occur.b) Any sensible suggestions acceptable, e.g. hallucinations, fevers, nervousness and para-noid, heart racing etc.

IS ALCOHOL REALLY THAT GOOD?

1 a) 30%

2 a) The temperature of the drinkb) Your eye colour.

3 Getting drunk can catch you by surprise. At first the drink just makes you relaxed. You feel more sociable and may be having a good time with friends. A few more drinks and you start to feel sleepy - but you are keen to keep on partying. More drinks and you start to get confused and unsteady on your feet. It is even more difficult to control your drinking no and soon you have drunk enough to pass out.

4 a) Alcohol can make you less nervous and shy in company. Many alcoholic drinks taste good and sharing them with friends is good fun.b) Large amounts of alcohol can cost a lot of money, can lead to obesity and other diseases (including fatal liver disease). You can also be a danger to yourself and others when you are drunk.

A NAIL IN THE COFFIN

1 It is very addictive and can cause high blood pressure.


2 a) Carbon monoxide.b) Hydrogen cyanide.

3 Smoking is one of the greatest threats to health that we bring on ourselves. Smokers choose to breathe in a range of poisons. Carbon monoxide acts immediately to damage your blood. Nicotine can cause addiction. Other chemicals cause cancers – maybe many years later. The most obvious effect is the cough. The smoker’s cough is caused by sticky black tar clogging up the lungs.

4 a) The cigarette smoke damages the small hairs that clear the lungs of mucus. The mucus traps bacteria which stay in the lungs and grow to cause bronchitis.b) Heart disease, lung disease, cancers.

ANOTHER NAIL IN THE COFFIN

1 a) A risk is something that might happen and could lead to damage.b) Any sensible answers acceptable, e.g. crossing the road, flying in an aeroplane, smoking.

2 A Smoking increases the risk of heart disease. TRUEB Cigarette smoke contains the addictive drug nicotine. TRUEC Smoking is the major cause of lung cancer. TRUED Everyone who smokes develops lung cancer eventually. FALSEE Some filters in cigarettes clean all the dangerous chemicals out of the smoke. FALSE

3 a) Non-smokers breathing in smoke from smokers’ cigarettes.b) To protect non-smokers and to encourage smokers to give up.

4 a) Any sensible answers acceptable, e.g. change to a milder brand, smoke fewer cigarettes.b) Any sensible answers acceptable, e.g. it is addictive so difficult to give up, it costs a lot of money, it can lead to many diseases.

CANNABIS

1 a) A plant called Cannabis sativa.b) (1) Feeling giggly (2) Sleepiness.

2 A Cannabis is an illegal drug. TRUEB All cannabis users move on to harder drugs like heroin and cocaine. FALSEC Cannabis is an addictive drug. FALSED Most cannabis is taken in smoke in the UK. TRUEE It is legal to own cannabis for personal use in the UK. FALSE

3 (1) Joints contain tobacco which is a dangerous drug.(2) It is not always possible to tell the dose of the drug in the joint.

4 a) Any sensible answers acceptable, e.g. it is much less dangerous than drugs like heroin and may be safer than some legal drugs (e.g. cigarettes), it would make cannabis easier to regu-late, it would reduce criminal activity linked to drugs.


b) Accept any sensible answers, e.g. cannabis can do damage to people, no dangerous drugs should be legal at all.

JUST SAY NO

1 a) Any sensible answers acceptable, e.g. (1) for a ‘dare’, (2) because others around them do, (3) because they want to see what its effects are.b) Any sensible answers acceptable, e.g. (1) because you are physically addicted to them, (2) because you may be involved with a crowd who all take illegal drugs.

2 Morphine poppy. (Papaver somniferum)

3

Drug Effect

Heroin Depression and relaxation

Cocaine Makes user feel very energetic and excited

LSD Gives user hallucinations

Cannabis Makes user feel relaxed, they can giggle a lot

4 a) Any sensible answers acceptable, e.g. provided with treatment, sent to prison to deter oth-ers.b) Any sensible answers acceptable, e.g. provide treatment, sack them because they could not do their job.

DETECTING YOUR ENVIRONMENT

1 a) Sight, hearing, taste, touch, smell.b) Any sensible answer acceptable with a reason.

2

Type of stimulus Sight Hearing Touch Taste Smell

Objects or events far away

√ √

Chemicals √ √

Objects touching the body

√ √

3 Brain and spinal cord

4 Correct sequence:Stimulus: sight of approaching car


Sense organ: the eye detects the stimulusNerve network: carries information to the brainBrain: decides what to do and sends out a nerve signalNerve network: carries information from the brainMuscles: contract more quickly to move you to safety

5 a) The nerves cannot make the muscles contract.b) Multiple sclerosis also damages the nerves from the eyes but MND does not.

BEING IN CONTROL

1 a) (1) Coordinate muscles, (2) interpret nerve signals from the sense organs, (3) think.b) 1.5 kg.

2

3 a) The blood supply is blocked so the brain does not get enough oxygen and dies.b) Problems with sight

4 a) The electrodes are used to stimulate the part of the brain under study and the scientists can see what happens to the person’s body or feelings.b) They can plot which parts of the brain are damaged and then see which parts of the body seem to have failed.

WHAT ARE WE BORN WITH?

1 Any sensible answers acceptable, e.g. blink reflex, babies feeding, pulling your hand away when you touch a hot object.

2 Innate means something you are born with, e.g. a reflex which does not need to be learned.

3


Reflexes Protects the body against...

Blinking Dust getting into the eye

Being sick Poisons passing into the body

Sneezing Dust getting into the lungs

4

Innate re-flexes

Learned beha-viours

Are they very rapid? yes no

Are they mainly concerned with protection?

yes no

Do they improve with practice? no yes

Do you need to think about them? no yes

5 a) A stimulus is something that we can detect, e.g. a sound or a sight that produces a re-sponse.b) If the young had to learn the reflex they may be damaged before learning had occurred.

LEARNING BEHAVIOUR IN ANIMALS

1 b Crime and punishment

2 The dog trainer would give the puppies praise and a treat when they got the trick right.

3 A lot of what seems like play in young animals is really about learning. Young lion cubs, for example, learn about what their bodies can do and how to move quickly and use their claws and mouth for attack by play fighting with their siblings. Trying to track prey, and perhaps failing, is also a learning experience. By the time they are adult they will have prac-tised many of the skills they need to stay alive.

4 a) The trainer could give the dog praise and treats when it obeyed and punish it when it dis-obeyed.b) It can hurt the animal and only teaches them what not to do rather than what to do.

AGGRESSION

1 Any sensible answers acceptable, e.g. fear, being annoyed.

2 (1) Attacks from other animals during mating season(2) Protecting a territory(3) Fear

3 a) The colour red seems to be the key stimulus for this behaviour.


b) See if blue or green coloured models produced an aggressive response in the robins.

4 There seem to be a number of things that always cause aggression in animals. One example is defending territory. Many animals will display aggressive behaviour to other animals en-tering their territory. The response is particularly strong during the breeding season. Other stimuli to aggressive behaviour include fear, protection of young, establishing dominance in a pack or simply attacking an animal to kill it and eat it.

5 a) Any sensible suggestions acceptable, e.g. they can both be caused by fear or invasions of territories or competition for a mate.b) Any sensible suggestions acceptable, e.g. humans can sometimes control their fear or can talk about things rather than just fighting.

HOW DO I LEARN?

1 (1) Long term memory(2) Short term memory

2

3 There seems to be two stages to learning a list of dates: getting the facts into short-term memory and then transferring them into long-term memory. Loading into short-term mem-ory is fairly easy but the memory fades after a few days. This is because no new nerve path-ways have been made. Loading facts into long-term memory is more difficult and needs lots of repetition. Long-term memory seems to change the ways nerve cells are linked together and can last for many years.

4 a) Any sensible suggestions acceptable, e.g. rewards for success, punishments for failure.b) It seems to be linked with memory.

EFFECTIVE LEARNING

1 Using a diagram instead of just text to help you remember something.

2 Any sensible suggestions acceptable, e.g. a revision timetable, working with a friend, work-ing through sample tests.

3 Auditory learning

4 a) A way of showing how the big ideas in a topic link together


b) Any sensible answer acceptable with a reason.

5 a) Any sensible answer acceptable.b) Depends on answer to a).


VARIATION

WHY ARE WE SO DIFFERENT?

1 a) Any sensible answers acceptable, e.g. height, weight, eye or hair colour.b) Any sensible answers acceptable, e.g. height, weight, eye or hair colour.

2 Any sensible answers acceptable, e.g. different genes, different diets, interests in sports and fitness, family background etc.

3

Group 1: controlled mainly by the environment

Group 2: controlled by envi-ronment and genes

Group 3: controlled mainly by the genes

Ability to play the pianoAmount of fat under the skinBeing able to speak French

Height Skin colourHair colour

Eye colourGender (male or female)Blood group

4 a) Differences in their environment will affect what they look like, e.g. one may have had an accident and so have a scar.b) Through the eggs and sperm.

HOW TALL IS THIS GROUP?

1 Variation means the differences between animals or plants of the same species or type.

2 a) Any sensible answers acceptable, e.g. there are no defined colours to compare them with, some people have more than one colour of hair, some people have dyed hair.b) Any sensible answers acceptable, e.g. use a colour chart, ignore dyed hair.

3 c Accurate and relevant

4 Scientists like to convert observations into numerical scores. So, height is not recorded as ‘tall’ or ‘short’ but as 150 cm or 175 cm. This means that all scientists around the world know what the researcher meant when they described a particular height. Using words might be confusing – a tall person in China might be considered medium height or even short in the USA. Some differences are very difficult to convert to numbers. Is a bluey-green eye colour blue or green? This is why scientists often choose features to research that are easy to measure.

5 a) The effect of any freak results is lower when there are many data points.b) Larger samples usually produce more reliable data because any freak results are diluted by the others in the sample.

WHAT CAN TWINS TELL US?

1 The genes of identical twins are identical.

2 About 3333 births are twins so there will be about 1667 sets of twins (1 set per two births).


3 a) Eye colour and blood groupb) Languages spokenc) Not a large enough sample – these twins may be special in some way.

4 a) The differences show the effect of the environment better.b) You may have genes that would make you tall but if you do not have enough food or are very ill as a child you may not reach your full potential height.

IT CAME FROM MY PARENTS

1 a) Any sensible answers acceptable, e.g. eye colour, blood group, skin colour.b) Any sensible answers acceptable, e.g. ability to play piano, being overweight, ability to speak French.

2 Smallest to largest:Gene Chromosome Nucleus Sex cell Body cell

3 a) Acceptable: Brown:Brown and Brown:Blue b) Blue:Blue

4 A dominant gene takes control of the cell’s development even if a recessive gene is also present, e.g. brown is dominant to blue in eye colour.

5 a) If the brown-eyed parents both had Brown:Blue genes they could each pass a blue gene onto their child who would then have blue eyes.b) Each parent provides information contained in genes (located in the chromosomes of the sex cells). Each parent provides half of the full amount of chromosomes, and during fertil-isation the sex cells join together to create an offspring with a full set of chromosomes and genetic information from both parents. This is called ‘inheritance’.

NATURAL CLONES

1 b Have the same genes

2 Plants grown from runners all have exactly the same genes because they are from the same parent plant. Plants raised from seeds have different genes because they have been produced by two parents.

3 There are two methods of reproduction: asexual and sexual. Asexual reproduction is much more common in plants and microorganisms. Parts of the organism bud off to form com-plete new individuals with exactly the same genes. Asexual reproduction produces clones. In sexual reproduction the offspring are genetically different from each other (unless they are twins!) and the parents.

4 a) A researcher takes a nucleus form one cell and inserts it into another cell which has had its own nucleus cut out.b) Sexual reproduction produces more variation which could lead to an improvement in the species. However, it requires two sexes which might make reproduction slower. Asexual re-production can produce large numbers of individuals very quickly. However these individu-


als are all genetically identical so if, for example, one catches a disease they probably all will.

DOG BREEDING

1 a) Accept any sensible suggestions, e.g.

Reasons for owning a dog. Reasons for not owning a dog.

likes animals, companionship allergic to dogs, expensive

b) Any sensible answers acceptable provided it has a reason.

2 A pedigree dog is produced when both parents comes from the same breed. A mongrel is produced when the parents are from different, or no, breeds.

3 Dog breeding is a good example of artificial selection. Human beings have chosen particu-lar dogs with the desired features to breed puppies from. This means the puppies have the same desirable features. It is possible to breed in certain features by allowing dogs with those features to breed with your chosen dog. It is also possible to breed out some features by not allowing dogs with these features to breed.

4 a) Inbreeding happens when parents are closely related.b) Inbreeding produces a very ‘pure’ breed that contains the desired characteristics the dog breeder is seeking.

TOPIC QUIZ – Drugs and behaviour

1 a) A chemical that can change the body’s chemistryb) Paracetamol, aspirin, penicillinc) Heroin, cocaine, marijuana

2 A stimulant gives you energy and speeds you up but a depressant calms you down.

3 Cancer, lung disease, heart disease, blood disorders.

4 a) Any sensible answers acceptable, e.g. to remove supply chain from criminals, it is less dangerous than some legal drugs.b) Any sensible answers acceptable, e.g. there are some concerns about dangers to mental health from cannabis, it is still a drug and risks are involved.

5 a) Sight, hearingb) Hearing, touchc) Sight, smell

6 a) An interruption of blood supply to a part of the brainb) The left hand side of your body is paralysed.

7 (1) Blinking(2) Pupil dilation/contraction(3) Pulling limbs away from hot object


8 Rewarding the dog with a treat when it does a trick.

9 It displays it red breast and sings loudly trying to force the intruder away.

10 Their short-term memory has been damaged but memories from many years ago that have already been loaded into long-term memory are easy to retrieve.

11 Cannabis has no harmful effects on adults. FALSE – cannabis may have harmful effects on

adults. Some people can drink five pints of alcohol in an hour and still be safe to drive. FALSE – it

is impossible to drink five pints of alcohol in an hour and still be safe to drive. Filters on cigarettes remove all the harmful chemicals from the smoke. FALSE – filters on

cigarettes reduce some of the harmful chemicals going into your body. It is impossible to learn a reflex – you must be born with it. FALSE – it is possible to

‘learn’ a conditioned reflex. The central nervous system consists of the brain and the sense organs. FALSE – the central

nervous system consists of the brain and spinal cord.

TOPIC QUIZ – Variation

1 a) Any sensible suggestions acceptable, e.g. blood group, eye colourb) Any sensible suggestions acceptable, e.g. ability to speak a languagec) Any sensible suggestions acceptable, e.g. body mass, fitness, skin colour

2 a) centimetres or inchesb) grams, kilograms or poundsc) any currency

3 Because they have exactly the same genes.

4 Carl Linnaeus

5 Mammals, reptiles, birds, amphibians, fish

6 Dig up dandelions of roughly the same size and age from two areas: damp areas and dry ar-eas. Measure the length of roots on each specimen and compare the average length for the damp area plants with those from the dry area plants.

7 The bl gene in the brown-eyed person with Brbl has been covered up the dominant brown gene.

8 A gene

9 They all have exactly the same genes.

10 a) It can lead to deformities in the inbred population as recessive, damaged genes collect in the population.b) To choose particular desirable features, e.g. coat colour or eye colour.


11 Leaf size is not affected by the environment. FALSE – Leaf size is affected by the environ-

ment. Darker areas tend to have larger leaves. Scientists give organisms special names so that ordinary people do not know what they are

talking about. FALSE – Scientists give organisms special names so that scientists from all over the world, who may speak different languages, know which organism they are talking about.

Twins always look exactly the same as they get older. FALSE – Twins look similar but as they get older may become more dissimilar as the effects of the environment increase.

Fish belong to the reptile group. FALSE - Fish do not belong to the reptile group. Chromosomes are larger than genes. FALSE - Genes are larger than chromosomes.


CHEMICAL PATTERNS

THE ALKALI METALS

1 Blue

2 The density of a material is its mass divided by its volume.

3 lithium + water → lithium hydroxide + hydrogensodium + water → sodium hydroxide + hydrogenpotassium + water → potassium hydroxide + hydrogen

4 a) Hydrogenb) Very violently, probably explode

5 a) As you go down the Group I metals, the reactivity increases.b) Because Group I metals react with air and water.

WORD AND SYMBOL EQUATIONS

1

Symbol Chemical

H2 Hydrogen gas

O2 Oxygen gas

Na Sodium

Zn Zinc

H2SO4 Sulphuric acid

2 a) carbon + oxygen → carbon dioxideb) sodium + water → hydrogen + sodium hydroxidec) zinc + sulphuric acid → zinc sulphate + hydrogen

3 a) The number of atoms on one side of a symbol equation must be the same as on the other. TRUEb) There must be more atoms at the start of an equation than at the end. FALSEc) Symbolic equations show the number and the types of atoms in a reaction. TRUEd) You have to know the formula for the chemicals involved to write an equation using sym-bols. TRUEe) Word equations always run right to left. FALSE

4 a) They take less time to write than word equations and show the numbers of atoms involved in the reaction.b) A ‘balanced equation’ has the same number of atoms of each type on both sides.


REACTING METALS

1 a) Any sensible suggestions acceptable, e.g. milk, cheese, yoghurtb) Making teeth and bones

2 a) magnesium + oxygen → magnesium oxideb) calcium + water → hydrogen + calcium hydroxide

3 An element cannot be broken down into a simpler substance and contains only one type of atom.

4 a) More quickly than magnesiumb) MgO

5 a) Any sensible suggestions acceptable, e.g. calcium and magnesium both react with water and oxygen.b) Any sensible suggestions acceptable, e.g. calcium is a brittle greyish metal but magne-sium is silvery and bendy.

METALS AND ACID

1 Any sensible suggestions acceptable, e.g. (1) Measure how long the metal takes to disap-pear, (2) Measure the change in weight as the reaction proceeds.

2 a) To make the test fair.b) If he reused acid from previous experiments some of the acid would have been used up so the test would not be fair.c) Fastest to slowest:potassium, sodium, zinc, magnesium, iron, aluminiumd)

0

20

40

60

80

100

120

Aluminium Calcium Iron Magnesium Potassium Sodium Zinc

Metal

Tim

e to

dis

solv

e (s

)

e) Hydrogen


3 The reactivity series is a list of metals ranked by their reactivity. The most reactive metals come at the top of the list and the least reactive at the bottom. Group I metals tend to be at the top. Aluminium is a strange result. It does not dissolve in acid. This is because it is nat-urally covered with a thin layer of aluminium oxide that protects the metal from the acid. If this oxide layer is removed the metal reacts quite quickly.

4 a) Reactive metals would react with oxygen and moisture and so would corrode away.b) Because they can use it to predict unknown reactions.

ACID CONCENTRATION

1 a) A concentrated acid contains a lot of acid and very little water in the solution.b) They need less washing up liquid for each set of dishes so it lasts longer.

2 Mix it with a measured amount of deionised water.

3 You cannot keep it in anything – it would dissolve the container!

4 a) Pure waterb) The higher the concentration the faster the reaction.c) Acceptable: 10 or 11 seconds

5 a) Any sensible suggestions acceptable, e.g. wear goggles, take special care not to get any on your skin.b) Adding a measured amount of water to a measured sample of the 100% acid. The differ-ent concentrations depend on how much water is added.

DISPLACEMENT OF METALS

1 In a displacement reaction, one atom replaces another in solution forcing it to come out of solution.

2 a) The iron nail goes brown.b) The solution becomes paler blue.

3 A displacement reaction happens when a more reactive metal takes the place of a less reac-tive metal in a compound or solution. Zinc is more reactive than copper. If you put a few zinc granules in a copper sulphate solution the zinc forces the copper out of solution. The liquid becomes zinc sulphate solution.

4 a) A reactive chemical takes part in chemical reactions very easily.b) Drop the unknown metal into a solution of copper sulphate. If the copper comes out of so-lution and solution changes colour, the metal is more reactive than copper.

PREDICTING REACTIONS

1 The more reactive metal forces electrons onto the less reactive one converting it to solid metal.


2

Metal in solution Solid metal added Will the new metal displace the one in solution?

Sodium Iron No

Copper Zinc Yes

Zinc Calcium Yes

Calcium Gold No

Potassium Magnesium No

3 ‘I know what next week’s winning lottery numbers will be!’ is not a scientific prediction. And you probably wouldn’t believe it! But scientists make predictions every day in their work. They look for patterns and then suggest what would happen in a new situation using the patterns as a guide. You have probably made some sensible predictions yourself about the ways different metals react in acids based on the reactivity series.

4 a) Acid gases damage plants by poisoning the cells that absorb carbon dioxide from the air. Acid gases also dissolve to make acids in the soil, which releases poisonous minerals like aluminium, which the plants then take up through their roots.b) Any sensible suggestions acceptable, e.g. compare the health of pine trees by counting the number of leaves or height of trees planted at the same time in areas damaged by acid rain and those in clean areas.

CORROSION OF METALS

1 a) When a metal corrodes, it reacts with air an moisture to change into another compound – usually a powder or crystals – and so becomes weaker than the original pure metal.b)

Corrode easily Do not corrode

ironmagnesium

steel

goldaluminiumtitanium

2 Gold never corrodes so will last forever.

3 Any sensible suggestions acceptable, e.g.

Use Metal Reason for your choice

A piece of jewellery Gold, silver Expensive, corrode very slowly or not at all

A bucket Iron, steel Cheap and strong

A wire to carry electricity in a computer circuit

Copper, aluminium Good conductors of electricity


Use Metal Reason for your choice

A replacement knee joint Titanium Very strong and does not react with any chemicals in the body

A roof for a large department store

Steel, copper, alu-minium

Strength, easy to form into shapes

4 a) Reactive metals would react with the air or moisture in the machine and the machine part would degrade.b) It is cheaper than metals like aluminium which does not rust.

HOW TO STOP CORROSION

1 (1) Air (oxygen), (2) Water

2 (1) Cover it in grease, (2) Paint it with a waterproof paint, (3) Coat it in another metal, e.g. zinc.

3 Paint

4 Aluminium is a strong, lightweight metal used to build cars, planes and trains. It also cor-rodes very slowly because it is covered with a thin layer of aluminium oxide. This oxide coating is tough and prevents more oxygen getting at the metal underneath. Some alu-minium parts are anodised to increase the thickness of this coating for even better protec-tion.

5 a) Zinc stops it rusting.b) A thin layer of tin is used to cover the steel the cans are made from.


CHEMICAL REACTIONS

METALS AND NON-METALS

1 a) An element cannot be broken down into a simpler chemical substance and contains only one kind of atom.b) Metals and non-metals

2 a) Usually solid at room temperature. METALSb) Conduct heat well. METALSc) Some are gases at room temperature. NON-METALSd) Conduct electricity well. METALSe) Do not conduct heat well. NON-METALSf) Cannot be polished to a shine. NON-METALSg) Can be beaten into flat sheets without breaking. METALSh) Do not conduct electricity well. NON-METALSi) Can be stretched into thin wires without breaking. METALS

3 a) Mercury is the only liquid metal.b) Sodium is lighter than water and reacts violently with it.c) Graphite (carbon) can conduct electricity.

4 a) If we only look at one property (e.g. is it solid at room temperature?) some non-metals would be classified as metals and mercury, which is a metal, would be classified as a non-metal.b) In the area where metals begin to change into non-metals – roughly Group IV.

ACIDS, ALKALIS AND BASES

1 a)

b) Neut-ralise: what does an acid do to an alkali when they react to-gether?


2 a) Bases are solids and do not dissolve in water, alkalis are substances that dissolve in water to make a solution that turns red litmus paper blue.b) The sulphuric acid reacts with the basic copper oxide to produce blue copper sulphate and water.

CARBONATES AND ACIDS

1 (1) It dissolves in water to make an acid solution. (2) It turns limewater milky.

2 Any sensible suggestions acceptable, e.g. (1) the marble chips disappear, (2) a gas is given off, (3) the weight changes.

3 Some types of fire extinguishers contain a powdered carbonate and a dilute acid solution. When these are mixed they produce carbon dioxide gas which can be used to force the extin-guisher liquid, usually water, out of the container at high pressure. The higher the pressure the further the water jet will go – so there is no need to stand too close to the flames.

4 a) Drip hydrochloric acid onto a sample of crushed rock. If it gives off carbon dioxide (it fizzes) the rock contains carbonate.b) Use an electronic weighing machine, as the reaction proceeds the weight goes down. Measurements taken every 20 seconds or so will allow you to plot a graph of the reaction and the steeper the graph the faster the reaction.

SALTS

1 Hydrogen

2

Acid Salts

Sulphuric Sulphates

Carbonic Carbonates

Nitric Nitrates

Hydrochloric Chlorides

Acetic Acetates

3 a) How quickly it crystallises from solution: slower crystallisation produces bigger crystals than faster crystallisation.b) Make a very concentrated salt solution and then let the water evaporate very slowly (e.g. don’t heat it or put it in direct sunlight).

4 metal + acid → salt + watermetal + metal carbonate + acid → salt + carbon dioxide + wateracid + base or alkali → salt + water


5 a) Add excess copper oxide to a beaker of sulphuric acid. When the reaction has finished and some copper oxide is left on the bottom of the beaker, filter off the clear liquid and heat it gently to drive off the water and leave the solid copper sulphate.b) If there is any unreacted copper oxide in the solution all the acid must have been used up.

MAKING A SALT

1 The crystals of one type of salt are all the same shape. TRUEDifferent salts have different colours. TRUEThe crystals of one type of salt are all the same size. FALSESlow evaporation produces the largest crystals of any salt. TRUEAll salts are white in colour. FALSE

2 A neutralisation reaction occurs when an acid reacts with an alkali.

3 Any sensible suggestions acceptable, e.g. Mistake 1: some of the acid may have been left over. Mistake 2: heating strongly could damage the magnesium sulphate.

4

Acid Metal oxide Salt

Sulphuric acid Copper oxide Copper sulphate

Nitric acid Lead oxide Lead nitrate

Sulphuric acid Potassium oxide Potassium sulphate

Hydrochloric acid Calcium oxide Calcium chloride

5 a) If excess metal oxide is used you can be sure that all of the acid has been used up. b) The excess oxide can be filtered off because it will not dissolve.

PRECIPITATING SALTS

1

Scientific word Meaning

Soluble Something that will dissolve.

Solution A liquid that contains a dissolved substance.

Insoluble Something that will not dissolve.

Solvent A liquid that can dissolve something.

Solute The substance that dissolves in a solvent.

2 a) A pigment is a substance that has a colour.b) Pigments are used in dyes for clothes, paints and even in make-ups like lipsticks.


3 When two solutions are mixed, the substances they contain are all mixed up. Sometimes these substances break apart into separate bits – this is what happens when they dissolve. If the separate bits can join together to make an insoluble substance they do. The insoluble substance comes out of solution as a precipitate.

4 a) Mix solutions of lead chromate and barium sulphate.b) Barium chromate

USING SALTS

1 a) A mordant is a chemical that can help a pigment to bind chemically to fabrics so that they ‘fix’ the colour of the fabric even when the fabric is washed in clean water.b) Aluminium sulphate

2 Correct sequence:Mine the rock saltDissolve the rock salt in waterFilter off the insoluble particlesHeat the salt solution with powdered charcoalFilter off the powdered charcoalHeat the salt solution gently to evaporate the water

3 Salt has a long history. Long before chemists were making it in laboratories people were collecting it from around shallow lakes. Salt in the soil would be washed into the lakes and be left behind as the water evaporated. In ancient Egypt they collected alum in this way. In Chile there was so little rain in the deserts that the salt was not washed away and could be gathered from the ground as saltpetre or Chile nitre.

4 a) The metal has a valency that is equal to the number of the group it comes from. If you also know the valency of the salt group you can work out the formula by writing a balanced equation.b) The least soluble salts come out of solution first followed by the more soluble salts as the water evaporates.

TOPIC QUIZ – Chemical patterns

1 Rusting

2 Oxygen, moisture, not too cold.

3 a) Any three from: lithium, sodium, potassium, rubidium, caesium or francium.b) React violently to give off hydrogen and form an alkaline solution.

4 potassium + sulphuric acid → potassium sulphate + hydrogen

5 Because gold does not dissolve in very concentrated acid.

6 a) A list of metals sorted by their reactivityb) Acceptable: potassium or sodiumc) Acceptable: copper or gold


7 Strength is a measure of how low the pH of the acid is, concentration is a measure of how much acid the solution contains compared with the water.

8 Any two from: beryllium, magnesium, calcium, strontium, barium or radium

9 Any sensible suggestions acceptable, e.g. not toxic, does not corrode easily, can be polished to a good colour, etc.

10 Paint them, plate them with a metal that does not rust.11

Magnesium displaces copper from a solution. TRUE Reactivity increases as you go down the Group I metals. TRUE Aluminium is often used for buildings because it is light, strong and does not corrode easily.

TRUE The reactivity series allows you predict some reactions. TRUE For word equations you do not need to know the formula for the chemicals involved but in

symbol equations you do. TRUE Alkali metals react very quickly with water but do not react with oxygen at all. FALSE – al-

kali metals react readily with both water and oxygen. The chemical formula for magnesium oxide is MgO2. FALSE – the chemical formula for

magnesium oxide is MgO. Gold displaces cheaper metals from solution. FALSE – gold displaces less reactive metals

from solution. You can stop iron rusting by treating it with strong acid. FALSE – a strong acid would cor-

rode iron. Painting iron stops rusting because the paint reacts with the iron. FALSE – it is because the

paint forms a protective layer between the iron and the atmosphere.

TOPIC QUIZ – Chemical reactions

1 Conduct heat and electricity well, can be drawn into wires or beaten into flat sheets, solid at room temperature.

2 (1) Neutralise acid with a measured amount of alkali and evaporate solution to dryness.(2) React excess metal oxide with an acid, filter off residual oxide and evaporate solution to dryness.

3 Precipitation is the coming out of solution of an insoluble substance when two solutions are mixed.

4

Acid Salts

Nitric acid Nitrates

Sulphuric acid Sulphates

Hydrochloric acid Chlorides

5 Mix equal volumes of equal concentration hydrochloric acid and sodium hydroxide solution. The resulting mixture should be neutral (check this with an indicator paper and add acid or


alkali dropwise to adjust as required). Heat solution to dryness which will give dry sodium chloride.

6 a) A coloured chemicalb) In dyes and paints

7 a) A solution forms when a solute dissolves in a liquid, e.g. sugar dissolving in water.b) The solvent is the liquid that dissolves something to make a solution.c) The solute is the substance that dissolves in a liquid to make a solution.

8 metal + acid → metal salt + hydrogenacid + alkali → salt + water

9 Mix excess copper oxide with sulphuric acid. Filter off the excess copper oxide and evapo-rate the solution to dryness, not heating too strongly.

10 Soluble salts: sodium chloride, potassium chlorideInsoluble salts: barium sulphate, calcium carbonate

11 An insoluble salt can be made by precipitation. TRUE Water and salt is always produced when an acid and an alkali react. TRUE The largest salt crystals are made when a solution evaporates slowly. TRUE Ancient Egyptians made salt by evaporating seawater. TRUE Sodium chloride is insoluble. FALSE – sodium chloride is soluble. All sodium salts dissolve in water. TRUE Copper sulphate can be made by mixing copper and sodium sulphate. FALSE – it can be

made by the reaction between sulphuric acid and a copper compound such as copper oxide. There are no salts of acetic acid. FALSE – there are salts of acetic acid. Precipitation is another word for dissolve. FALSE – precipitation means the process of

forming a chemical precipitate. All salts are white in colour and dissolve in water. FALSE – salts can be a variety of differ-

ent colours and are not all soluble in water.


PRESSURE, FORCES AND MOMENTS

PRESSURE POINTS

1 The wide area of the boards spread the pressure evenly over a large surface so the force is low and they do not sink into the soft snow.

2 a)

3 a) The wide tyres spread the weight of the vehicle over a wider area so reducing the force that will tend to make the vehicle sink into the snow.b) The force that cuts through a body should be as high as possible to make the cutting easier. By having a narrow edge to the blade the force is large and acts through a narrow area. If it were a blunt edge the force would be lower but act over a wider area and so not be as good at cutting.

PRESSURE IN GASES

1 Any sensible suggestions acceptable, e.g. (1) Wind can move things like windmills or kites, (2) we can feel something moving against our skin when we stand in the wind, (3) you can fill a balloon with air and put it underwater and it does not collapse.

2

Increase pressure in the balloon Decrease pressure in the balloon

push more particles into the balloondecrease the size of the balloon

take particles out of the balloonincrease the size of the balloon

3 A bicycle tyre depends on pressure to provide a firm but comfortable ride. Particles of gas in the tyre are constantly colliding with the wall of the tyre. These tiny impacts push the tyre wall outwards to give a firm ride. To give a harder ride simply add more particles. And for a softer ride – let some of the air out.

4 a) Air moves from areas where the pressure is high to areas where it is lower. This move-ment of air is what we call wind.b) As you go up a mountain the air pressure gets lower because there are fewer particles of air there. This means that there is less oxygen available for the mountaineers to breathe.


PRESSURE IN LIQUIDS

1 Compress means to squeeze on something2 a)

b) The higher pressure at the bottom of the cylinder pushes the water out of the cylinder with more force so it goes further.

3 A hydraulic press uses liquids to transmit forces. A narrow piston is squeezed with a small force and this passes through a liquid into a much larger piston. If the large piston has a sur-face area that is 100 times the narrow cylinder it will be pushed with 100 times the force. In this way whole cars can be crushed into something the size of a school desk!

4 a) The amount of water above the diver increases as the diver goes deeper. This produces a greater pressure.b) If the air pressure were normal atmospheric pressure, the pressure of the water would crush the diver’s lungs.

TURNING FORCES AND MOMENTS

1 a) A moment is the effect of a turning force; it is the force multiplied by the distance to the pivot.b) A force × the distance to the pivot

2 The longer spanner produces a greater turning force because the distance from the applica-tion of the force to the pivot is greater than in the smaller spanner.

3 A tightrope walker uses a long pole to help them balance on the rope. They change the length of pole on either side of them. The longer length means a greater turning force acting down on that side. By moving the pole backwards and forwards through their hands, they keep the moments balanced. A longer pole makes it easier to walk on the rope than a shorter pole.

4 a) The heavier person should sit nearer the pivot than the lighter person.b) The turning effect is greater at the handle because it is a longer distance to the pivot than near the hinge.


THE BODY MACHINE

1 A lever is a solid rod which is used to magnify or reduce a force acting at a point.

2

3 Muscles can only contract about 10% of their total length. They pull on bones near the joint so that the other end of the bone can move a much longer distance. The biceps contract by about 3 cm but the hand moves through up to 50 cm. The bones of the lower arm act as a lever to magnify the movement.

4 a) The load is the force or object that has to be moved; the effort is the force that is trying to move it.b) Because muscles can only pull not push, wherever one muscle moves a bone, a muscle acting in the opposite direction is needed to pull it back again.

SPEEDY SUMS

1 a) A Distance ÷ timeb)

Distance measured in Time measured in Speed measured in

miles hours miles per hour

metres seconds metres per second

centimetres year centimetres per year

2 Acceleration is an increase in the speed or velocity at which an object is moving.


3 If you stand still in a descending lift the forces between you and the floor are balanced – you are not moving compared with the floor. Even the forces between the moving lift and the cable holding it up are balanced – the lift moves down at a constant speed. When the force of the cable pulling up starts to increase, the upwards and downwards forces are unbal-anced and lift slows to a stop at your chosen floor.

4 a) The cameras take two pictures at measured times. The speed of the car can then be calcu-lated by seeing how far it has moved across the lines on the road.b) Measure the distance from the place it started falling from the branch to the ground. Then measure the time it took to fall and divide the distance by the time.

DISTANCE-TIME GRAPHS

1 A variable is something that can have a set of different values, e.g. colour is a variable be-cause it can be red, green, yellow etc.

2 a)

0

100

200

300

400

500

600

700

800

900

1000

1 2 3 4 5 6

Time (mins)

Dist

ance

trav

elle

d (m

)

b) 870 metresc) Roughly two and a half minutes (two to three minutes acceptable).d) Between two and three minutes into the walk.e) The walker covers much less distance in that minute than in the others.

3 a) A steep slope in a distance-time graph tells you that the object is moving quickly.b) A horizontal line that is 5 minutes long (using the scale on the horizontal axis).


ENERGY TRANSFERS

SOURCES OF LIGHT

1 a) When an object gets hot enough it gives out light. TRUEb) Light from the Sun travels through space as rays. TRUEc) The Moon gives out light. TRUEd) The Moon produces its own light. FALSEe) All light on Earth comes from the Sun. FALSE

2 a) A luminous object gives out its own light – not just reflected light.b) Any sensible suggestions acceptable, e.g. (1) The Sun (2) A fire or flame (3) An electric light bulb.

3 a) Picture 2b) Picture 1c) Picture 3

4 a) The distance light travels through space in one year.b) It takes eight minutes for the light from the Sun to reach us. So the light we can see now was given out by the Sun eight minutes ago.

LIGHT AND PLANE MIRRORS

1

2 Any sensible suggestions acceptable, e.g. (1) A mirror to look at yourself (2) In periscopes or to see around corners (3) To reflect light into dark areas.

3

4 Scientists often use a light box to investigate how light is reflected by shiny surfaces. They mark the incoming ray and the point at which it hits the mirror. They mark the reflected beam in the same way. If you draw a perpendicular line straight out from the mirror at the point that the light ray hits it you can measure the angle of incidence. This is the angle between the perpendicular line and the incoming beam. It is always equal to the angle of re-flection on the other side of the perpendicular line.


5 a) The ray reflected from a flat mirror has the same angle to the mirror as the ray that hit it.b) The mirror reflects the view around the corner.

CURVED MIRRORS

1 a) Any sensible suggestions acceptable, e.g. (1) for seeing around corners, (2) to give a wide view of a shop for security.b) Any sensible suggestions acceptable, e.g. (1) a shaving mirror, (2) in a reflecting telescope.

2

3 Satellite dishes are concave mirrors for television waves. They reflect them to a focus where the receiver can detect them. This makes the signals at the receiver stronger than they would be without the dish.

4 a) The inside surface of a shiny spoon acts like a concave mirror, which magnifies the im-age.

b) The outside surface of a shiny spoon acts like a convex mirror, which gives a wider field of view with things looking smaller.

TOTAL INTERNAL REFLECTION

1 Any sensible suggestions acceptable, e.g. (1) For fibre-optic lamps or displays (2) High-speed communications networks.

2 If a ray of light hits the inner surface of the fibre at an angle below the critical angle it is re-flected back into the middle of the fibre.

3 B 1 mm

4 Optical cables are collections of optical fibres wrapped together. Each optical fibre can carry a separate signal coded as flashes of light. Equipment at one end encodes signals like sound or images into these pulses. At the other end the signal is decoded to recreate the ori-


ginal sound or image. Cables are now used instead of copper wires in almost all large tele-phone cables.

4 a) The signal travels faster and further in an optical cable and is less likely to be spoilt by noise in the system.b) The encoder converts the message into a series of light pulses. The decoder converts these flashes back into the original signal.

REFRACTION

1 a) Any sensible suggestions acceptable, e.g. (1) Camera (2) Reading glasses (3) Telescope.b) It bends light into a focus.

2 Refraction is the bending of light when it passes from one medium to another.

3


4 a) The light ray hits the new medium at an angle. If the new medium is more dense, the early waves are slowed down while the ones that have yet to hit the medium carry on at the same speed as before. This swings the whole beam around.b) The steeper the angle, the larger the time between one edge of the light ray hitting the new medium and the other one arriving.

ISAAC NEWTON THE ‘OPTICKIAN’

1 Any sensible suggestions acceptable, e.g. (1) Optics (2) Gravity (3) Mathematics.

2 Optician

3 red, orange, yellow, green, blue, indigo, violet

4 He recombined the scattered rays of coloured light with a prism to make a spot of white light.

5 a) The different colours in the white light are refracted by different amounts so the white light is spread out into its separate components.b) Red

COLOUR

1 a) Red, orange, yellow, green, blue, indigo, violet.b) Our brain interprets mixtures of these seven colours to allow us to see a wide range of colours.

2

Object Light falling onto it Light reflected from it

Splodge of red paint white red

Splodge of blue paint white blue

Splodge of green paint red nothing

Splodge of red paint green nothing

Splodge of blue paint blue blue

Splodge of green paint red nothing

4 Filters do not reflect light – they absorb it. So a red filter absorbs every colour in white light except for red. Scientists say the red light is transmitted by the filter. Remote controls that use a type of red light have a little red filter covering the light source to stop it being damaged. It lets the red light through unchanged. If you shone blue light through a red filter all of the light is absorbed – no light gets through.

5 a) When light is reflected by an object it bounces off it but when it is absorbed it cannot es-cape from the body. b) Green plants cannot absorb green light – which is why they look green.


USING COLOUR

1 a) (1) Red (2) Blue (3) Greenb) Because you can make any other colour from them by mixing them together in the correct proportions.


Warning sign or label Main colour used

Red traffic light Red

Radioactivity warning Often includes yellow

Laboratory safety warnings Often use orange backgrounds

3 Any sensible suggestions acceptable, e.g. a predator like a tiger which uses camouflage to creep up on prey or a prey animal like a zebra which uses camouflage to make it more diffi-cult for predators to see them.

4 Coloured lights are used in concerts to change the mood and the colour of the stage show. Blue light seems to make people sad while red. and yellow lights make for a more exciting mood. If the performer wears white the colours of their clothes change to match the light-ing. This may not be good – it doesn’t make them stand out! Sometimes the main performers are lit by powerful white spotlights – these show up any colourful costumes they are wear-ing very well against the background produced by the coloured lights.

5 a) The blue jeans absorb the red light and do not reflect any – so they appear to be absorbing all of the available light and look black.b) The colours are not sufficiently different to stand out well – particularly if they are seen in red or orange light.

SEEING THE LIGHT

1 a) Light enters our eyes to enable us to see objects. TRUEb) Light comes out of our eyes and we see things when that light hits them. FALSEc) Damage to the parts of the brain that interpret signals from the eye can make you blind – even if your eye works perfectly! TRUEd) All animal eyes have a lens and cells that can detect light. TRUEe) Human beings can see infrared and ultraviolet light. FALSE

2


3 a) (1) Compound eyes are small and simple; human eyes are large and complex. (2) Compound eyes contain many units; human eyes contain one main unit.b) (1) Both eyes have light-sensitive cells. (2) Both eyes have a type of lens.

4 (1) Large to let in as much light as possible, (2) with very sensitive light-detecting cells.

5 a) Too much light could damage the light-detecting cells so we have to be able to reduce the light getting into the eye. In dim light we need to be able to open the pupil as widely as pos-sible to let more light in to the light-sensitive cells or we would not be able to see in dim light.b) The pupil gets wider and the sensitivity of the retina increases. Images are more black and white than colour (which needs high levels of light to work properly).

RESISTANCE IN CIRCUITS

1

Circuit Current flowing

Powerful battery and low resistance wires Large current

Weak battery and low resistance wires Medium current

Powerful battery and medium resistance wires Medium current

Weak battery and high resistance wires No current

Discharged battery and low resistance wires No current

2 a) Any sensible suggestions acceptable, e.g. (1) Electricity flowing can make the wire hot (2) The thinner the wire the hotter it gets.b) (1) Light bulbs (2) Electric heaters.

4 a) The energy to heat the wire comes from the movement of electrons through the wire.b) If the wire is broken in parts the thin strands left might have to carry all of the mains elec-tricity. They could get hot and set fire the things like floorboards.

MODELLING CIRCUITS

1 A model toy car looks like a real car. In a scientific model the model behaves like the thing it is modelling. So, scientists can talk of charge flowing around a circuit as people pushing along a corridor. The charge does not look like people! But using a narrower wire is like making the corridor narrower. This reduces the number of people that can pass. In the same way, if you measure the resistance of the wire, it increases – the charge flowing is reduced.

2


Voltage Model

2 Tiny slipper

12 Slipper

240 Big boot

120 Medium boot

50000 Huge boot

3 The model behaves in the same way as the real situation but is easier to understand, because it is often a simple picture of a familiar process.

USING ELECTRICITY

1 (1) Easy to transport (2) Can be converted into many different forms of energy.


Device Uses

Electric motor 1: electric cars2: fans

Electric heater 1: cookers2: home heating

Loudspeaker 1: home stereos2: iPod headphones

3 A defibrillator uses an electric current to get the heart started after a heart attack. Two large electrodes are held tight to the chest of the patient and a sudden surge of electricity is passed from one electrode to the other. As it passes through the body it shocks the heart into beating again. Dials on the defibrillator allow the doctor to control the energy supplied by the shock.

4 a) Any sensible scenarios acceptable (and maybe some rather outlandish ones!).b) Depends on the identified needs but sensible suggestions acceptable, e.g. use a gas cooker instead of an electric one.

ELECTRICITY IN THE HOME

1 A carbon footprint is a measure of the energy a person or organisation uses. It is often used to show the impact of humans on the environment.

2 A the amount of electricity it uses

3 a


Voltage Current Power used

240 3 720 W

240 5 1200 W

240 10 2400

240 6 1440W

b Wattsc 1 kilowatt = 1000 W

4 a) Energy efficiency means we need to use less electricity to do the same job. This means we need to generate less and that means less fuel burnt and so less carbon dioxide released – the main cause of global warming.b) Any sensible suggestions acceptable, e.g. using the bus rather than the car, switching devices on standby off, changing to energy-efficient light bulbs etc.

TOPIC QUIZ – Pressure, forces and moments

1 d miles per gallon

2 0.5 miles per minute

3 To increase the force acting on their prey when they bite.

4 a)

b)

5 A hydraulic system uses pressure in liquid to transfer forces, e.g. a hydraulic car crusher.

6 Any three from: supporting the body, protecting body parts, attachment of muscles, blood production.

7 a) A solid rod used to magnify or change the direction of action of a force.b) Any sensible answers acceptable, e.g. a seesaw, a claw hammer, a spanner, nut crackers.

8 a) 200 Nb) Yes


9

10 To slow down

11 The deeper you go into the ocean the lower the pressure. FALSE – the deeper you go, the

higher the pressure. A longer handle on a spanned makes it easier to turn a rusted-in nut. TRUE Acceleration shows the increase in speed over time. TRUE Pressure is force divided by the area it acts over. TRUE A balanced force never produces movement. FALSE – a balanced force can result in move-

ment at a constant speed. Muscles always work in pairs to give to-and-fro movement. TRUE The smaller the area a force acts over, the greater the pressure. TRUE A bicycle tyre is filled with a liquid. FALSE – a bicycle tyre is filled with gas. Muscles can push or pull on a bone. FALSE – muscles can only pull on a bone. Oxygen cylinders for mountaineers contain gas at very low pressure. FALSE – they contain

gas at very high pressure.

TOPIC QUIZ – Energy transfers

1 Any sensible suggestions acceptable, e.g. the Sun, electric lamp, fire or flame, stars.

2 A flat mirror with no curvature

3 Refraction

4 A very important scientist who worked on a wide range of topics including optics, gravity and forces.

5 a) red, orange, yellow, green, blue, indigo, violet.b) red, blue, green.

6 Because it absorbs all the other colours of light and reflects the green light.7 a) A solid shape with straight sides, usually made of glass.

b) Splits it up into a spectrum.

8 Communication, carrying light to inaccessible places, fibre-optic lamps etc.

9 It reflects light from the Sun.

10 Light is a form of electromagnetic radiation. TRUE

D

S T


All lenses must let light through. TRUE The retina has nerve cells that can react to light. TRUE The light areas on an X-ray plate show where the X-rays have been blocked. TRUE Concave mirrors have the reflecting surface on the inside of the curve. TRUE Plane mirrors reflect light randomly. FALSE – plane mirror reflect light back at the angle at

which it hits them. Red objects absorb red light but reflect all other colours. FALSE – red objects reflect red

light but absorb all other colours. The lens in the human eye cannot focus red light. FALSE – the lens in the human eye can

focus all colours of light. Fibre optic cables can only carry red light. FALSE – they carry all the colours of light. Refraction is the scientific name for the way light bounces off a mirror.


HUMANS AND THE ENVIRONMENT

WHAT RESOURCES DO WE NEED?

1 a) Any sensible suggestions acceptable, e.g. (1) Food (2) Water (3) Shelterb) Any sensible suggestions acceptable, e.g. (1) Entertainment (2) Companionship / family


Human activity Possible environmental consequences

Mining Pollution from spoil heapsDestruction of farmland

Energy generation Atmospheric pollution – mainly acid gasesGlobal warming

Road building Habitat destruction

Farming Habitat destructionPollution in run-off from fields

3 (1) Run-off from fields (2) Acid rain (3) Outlets from factories or sewage works.

4 a) Deforestation means that the rain hits the soil directly and a lack of tree roots and other plants fails to stabilise the soil. When water rushes through it dislodges soil that would oth-erwise have been held in place.b) The basic premise of the proverb is that human beings often end up destroying the envir-onment by over-exploitation.

THE EFFECTS OF ACID ON PLANTS

1 carbon dioxide, nitrogen oxides, sulphur dioxide.

2 a) parts per millionb) Sulphur dioxide reduces the mass of tomatoes produced but has no apparent effect on the height of the plant.c) One plant may give a ‘freak’ response and distort the results.

3 In the 1980s and 1990s acid rain falling in Scandinavia killed millions of acres of forest. The trees began to die as toxic metals were released into the soil and rivers by the acids in the rain. Not only the trees but also the fish living in the rivers and lakes were killed. To make matters worse most of the acid gases responsible for the rain were blowing over from chimneys in the UK. Nowadays the problem is much less serious as we have learned to re-duce acid gases released to the atmosphere.

4 a) Acid gases mainly affect plants by damaging cells needed for uptake of carbon dioxide in the leaf and through poisonous metals which are released into the soil when the acidity rises.b) Look at the growth of pine trees in affected and unaffected areas, e.g. by measuring how long the needles survive before fall or the number of needles produced, the colour of the needles etc.


HOW CLEAN IS OUR AIR?

1 a) Fine particles of carbon produced by incomplete combustionb) The very small particles of smoke are solids but are so small and light that they can float in the air. Because they are so small they can flow around like a gas.

2 a) (1) Carbon dioxide (2) Water (3) Lightb) Light

3 a) The results showing the darker smudges – these must have come from needles with higher levels of soot.b) Leaves of different ages would almost certainly have gathered different amounts of soot anyway, because the longer the leaf has been present the more soot it will have gathered.c) To make the results comparable.

4 a) Soot is produced when fossil fuels like coal and oil burn in a limited supply of air.b) Any sensible suggestions acceptable, e.g. burn less fossil fuel, make sure burning fuels are well supplied with air – this reduces the production of soot.

WHAT HAPPENED TO THE ATMOSPHERE?

1 a) A fuel made from the remains of once-living creatures.b) (1) Coal (2) Oil (3) Natural gas

2 b Carbon dioxide

3 A mixture of smoke and fog

4 c Destruction of the ozone layer.

5 a) Catalytic converters convert acid gases like nitrogen oxides in exhaust fumes from motor vehicles into nitrogen and oxygen which are harmless.b) Burning fossil fuels increases the level of carbon dioxide in the air and this seems to stop heat escaping from the Earth. This is known as the greenhouse effect and seems to lead to global warming.

LOOKING AT YOUR SURROUNDINGS

1 a) Any sensible suggestions acceptable, e.g. grass, plantain, dandelion.b) There is a lot of trampling near the goalmouth and this kills the plants growing there to leave bare mud.

2 a)


0

1

2

3

4

5

6

Grass Bluebells Dogsmercury

Brambles Stingingnettles

Plant

Scor

e On or near the pathIn the woodland under the trees

b) Any sensible suggestions acceptable, e.g. (1) Bluebells can survive in darker areas than other plants. (2) Bluebells grow more slowly than other plants in lit areas so are crowded out.d) Depends on suggested explanation but sensible suggestions acceptable, e.g. to test for speed of growth of bluebells, measure length of leaf over time alongside similar measures for other plants.

3 a) Biodiversity is a measure of the range of living things in an area.b) Place the quadrat randomly on the ground and count the number of different species in the quadrat area each time. Do this about 30 times for each area. The area with the bigger biodiversity will have the higher average score.

CONSERVATION

1 Conservation means to manage the environment so that living organisms are not harmed by human activity.

2 Extinct: any sensible suggestions, e.g. sabre-toothed tiger, woolly mammoth, dodo.Endangered: any sensible suggestions, e.g. white rhino, Chinese river dolphins, pandas.

3

Things to do Things NOT to do

Clean up after their workRespect the environment they studyReturn any animals they trap to their natural Environment

Drop litterUproot plantsLight fires


3 In Aberglaslyn Pass in Snowdonia, conservation workers are busy cutting down and burn-ing hundreds of plants! Why? The plants they are clearing away are rhododendrons. These plants are invaders and grow rapidly to produce a very dense cover over the ground. They block the light for smaller plants and these die. This reduces the biodiversity of the area. In this case conservation of the area involves protecting some species by removing others.

4 a) We do not know what effect destruction of an area of natural habitat may have, e.g. the destruction of the Amazon rainforest may affect the atmosphere of the whole planet. Unique species may also be present in the area that might be very valuable to humans – we just don’t know it yet.b) People living in the area may have to change their farming or hunting habits to protect the organisms living in the area.

CAN WE HELP TO SAVE OUR PLANET?

1 Any sensible suggestions acceptable, e.g. (1) Overpopulation (2) Pollution (3) Destruction of arable land (4) Resources being used up.

2 a) There is an initial cost to ‘going green’. TRUEb) Extinct animals and plants can be recreated by scientists. FALSEc) The Earth is already past the point of no return. Humans will be extinct in 100 years. FALSEd) Most of the damage done to the planet is done by people in the rich countries taking more than the planet can support. TRUEe) There is enough space and resources on the planet to feed, clothe and house everyone ad-equately. TRUE

3 Any answers acceptable.

4 a) The effect at the local level can be significant and if everyone does it the total effect can be very significant.b) Any sensible suggestions acceptable, e.g. tax fuel more heavily to reduce use, ban ‘gas guzzler’ cars, provide more public transport, clean up waste and spoil heaps in old mining areas etc.


GEOLOGY

STUDYING SEDIMENTARY ROCKS

1 (1) Chalk (2) Sandstone (3) Mudstone

2 a) Sedimentsb) Pressure squeezes them together and then other minerals are deposited between the tightly packed sediments.c) Grains of sand

3

4 Rivers carry broken bits of rock towards the sea. Fast-moving rivers in the mountains and hills can carry heavier particles suspended in the water, but as the river slows down these start to fall out of suspension. You can see this after a flood – a thin layer of mud that has settled out of the flood waters covers everything. Over many years this layer can become quite thick and the weight of the top layers can press the lower layers together to make rock.

5 a) When rock is formed it usually forms on top of the layer below. This means the layer be-low must be older.b) Sedimentary rocks have not been subject to high temperatures and pressures which would destroy fossils. Also as the sediments settle out of water they will naturally cover any plant or animal remains on the sea or river bed.

MORE ABOUT SEDIMENTS

1 (1) Small crystals (2) Shiny surface (3) Very hard, does not crumble easily.

2 It suggests that coal is a type of rock that formed from plants found in swampy areas mil-lions of years ago.

3 a) Some fossils are complete body or body parts from organisms that lived millions of years ago. TRUEb) Some fossils are preserved evidence of dinosaurs – perhaps their footprints in mud. TRUEc) We can find fossils of every type of organism that ever existed. FALSE


d) Only extinct animals have fossils. FALSEe) Fossils are always found in rock that is the same age as the fossil. TRUE

4 a) The fossil record will always be incomplete because fossil formation is quite a rare event and we cannot be certain that all organisms have left fossils.b) Scientists can work out the size of the dinosaur, the structure of its foot (which may sug-gest it is a predator if it has sharp claws visible) perhaps even the weight and whether it was running or walking when it left the footprints.

MOUNTAINS AND FOLDS

1

Scientific word Meaning

Anticline A rise in the surface of the Earth caused by rock lay-ers being pushed together and folded upwards

Syncline A dip in the surface of the Earth caused by rock lay-ers being pushed together and folded upwards

Strata Layers of similar rock

Fold mountains Mountains made when rock strata are pushed together and move upwards.

Fault A crack in a rock layer.

2 a) In a cliffb) The ones nearest the bottom

3 Tectonic plates are giant slabs of rock in the Earth’s crust that move very slowly across the face of the planet.

4 a) Oil is less dense than rock and so move up between the particles – especially if water is present to move it towards the surface.b) The salty rock acts as an impervious barrier which traps the oil as a bubble of oil deep be-low the surface.

METAMORPHIC ROCKS

1 (1) Wet clay can be re-mixed with water but fired clay cannot be mixed with water to make a paste.(2) The colour often changes.(3) The fired clay pot is stronger than the wet clay.

2 a) (1) Heat (2) Pressureb) Because these rocks have also undergone a major change during their formation which changes their chemical and physical properties.


3

Sedimentary rocks Metamorphic rocks

limestonesandstonemudstone

marbleslate

gneiss

4 a) Metamorphic rocks have been formed by high pressure and/or high temperatures. These will almost certainly destroy any fossils present in the original rock.b) The crystals can become aligned in particular directions or grow between each other to produce a strong rock.

CRYSTALS IN IGNEOUS ROCKS

1 a) Lavab) Rock A

2 (1) Granite (2) Quartz (3) Pumice

3 Granite is made from three minerals mixed together. You can see the crystals of these min-erals in some granite rocks very easily – but only if they have cooled slowly underground. If they have cooled quickly the crystals will be too small to see without a hand lens or micro-scope. The minerals are quartz, mica and feldspar. You have almost certainly seen lots of quartz – it’s the sand on many beaches!

4 a) Basalt and obsidian are igneous rocks but can be rather glass-like (particularly obsidian) and do not look like many igneous rocks.b) Glass is made by heating quartz (sand) until it turns to a liquid.

VOLCANIC MAGIC

1 a) (1) Hot gases (2) Molten rock (lava)b) The flowing lava can move quite quickly and some of the ash and rock shot out when the volcano erupts can travel many miles. The dust and gases released can also make breathing difficult or dangerous.

2


3 Iceland is an island made by volcanoes and magma rising from the centre of the Earth. A huge valley running down the middle, called the Atlantic rift, produces new rock slowly every year. Iceland is actually getting wider by a few centimetres every year! The island is being slowly pushed apart as new rock is added. As well as this there are many volcanoes in Iceland and these spit out new rocks every year.

4 a) Eventually you would reach lava and the temperature would rise too high.b) There may be a build-up of lava underneath the volcano site and the drilling could disturb it and cause an eruption.

THE ROCK CYCLE

1 From the word ‘ignis’, which means ‘fire’ in ancient Greek (we also get the word ‘ignite’ from this word). Igneous rocks are all formed when rock is heated and melted and then al-lowed to cool.

2 a) The Earth formed as a giant liquid planet that cooled over millions of years. The outer surface cooled most to let igneous rocks crystallise from the lava.b) The igneous rocks were eroded away by the weather and the sediments washed down in streams and rivers. These sediments settled and formed sedimentary rocks.

3

4 The Earth. is not getting any bigger! So new rocks have to be made by recycling bits of old rock. This is actually going on all the time – but it is very slow. The rock cycle shows how igneous rocks are produced and then broken down by wind and rain to make sediments. These sediments are pressed into sedimentary rocks. Sedimentary rocks, in turn, may be changed by heat and pressure to form metamorphic rocks.

4 a) Because materials can pass round again and again.b) Water can dissolve some rocks (e.g. limestone) while others can absorb water and then split open if the water freezes to make ice. Running water can polish stones as well.


TOPIC QUIZ – Humans and the environment

1 a) Items in the environment that may be useful for humansb) Oil, natural gas, iron ore, etc.

2 Carbon dioxide

3 Reduced growth, reduced yield of valuable products (e.g. fruits).

4 Carbon dioxide, sulphur dioxide, nitrogen oxides

5 A quadrat

6 a) No members of the species are still aliveb) Any sensible suggestions acceptable, e.g. Tyrannosaurus rex, dodo, sabre-toothed tiger, etc.

7 Any sensible suggestions acceptable, e.g. produce lots of pollution and waste, use up re-sources, clear rainforests.

8 Any sensible suggestions acceptable, e.g. reduce amount of energy you use, walk instead of using the car, recycle more materials, etc.

9 Global warming is the measurable increase in average global temperatures. The greenhouse effect is one possible way to explain why it is happening.

10 Take a sample of the waste to another area where the plants were healthy. Treat them with the waste and see if they die.

11 Plants are adapted to live in their habitats. TRUE The woolly mammoth was the last surviving dinosaur. FALSE – The extinct woolly mam-

moth was a mammal, not a dinosaur. A renewable resource like wind power will never run out. TRUE There are enough resources for everyone on the planet to live like people in the rich world.

FALSE – the planet would run out of resources very quickly if everyone lived like people in the UK and USA.

Acid rain is caused by acid gases released from burning fuels. TRUE Soot has no effect on the growth of plants. FALSE – soot slows the growth of plants. Even very high levels of sewage is not a problem when it gets into rivers because the plants

can break it down. FALSE – high levels of sewage can cause many problems in a river. Oil, natural gas and coal are examples of fossil fuels. TRUE Sometimes conservationists have to kill plants that are threatening to take over a habitat.

TRUE Sulphur dioxide helps plants to grow. FALSE – it damages plants.


TOPIC QUIZ – GEOLOGY

1 Has layers in the rock, may contain particles, quite soft and easy to crumble.

2 Tectonic plates collided and the Himalayas were pushed upwards.

3 Marble, slate

4 The granite cooled very slowly.

5 A place where molten rock from deep in the crust can break out to the surface.

6 a) By weatheringb) By heat and/or pressure over many years

7 a) The preserved remains of a living thingb) There are no living creatures in the molten rock that cools to form igneous rock!

8 Size of dinosaur, stride length, possibly information about diet (claws would indicate a pred-ator)

9 Quartz, mica and feldspar

10 Layers of rock of the same type

11 Coal is a sedimentary rock. TRUE The oldest rock strata in an area are always nearest the top. FALSE – false, the rock strata

get older as you go down. Fold mountains are made by volcanoes. FALSE – fold mountains are made by plate move-

ments. Metamorphic rocks form when other rock types are heated or pressurised. TRUE You can recognise sedimentary rocks because they have large crystals. FALSE – you can re-

cognise sedimentary rocks because they have layers. Most geologists use hand lenses to study rocks because working outside in rocky areas has

damaged their eyesight. FALSE – they use hand lenses so they can see the detail of the rocks.

A fault is an area where the rock strata have split vertically and moved out of line. TRUE Igneous rocks form when molten rock cools to become a solid. TRUE We have fossils for every creature that has ever lived on Earth. FALSE – we believe that

many creatures have lived on Earth for which we have no fossils. People who study rocks are called geologists. TRUE

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