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Measurement and physical quantities

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"Measurement and Physical Quantities".

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Notes for teachers - module 1"Measurement and physical quantities"

The module has the following structure:- each theme is covered on a number of pages.- each individual experiment, item or study subject has its own page. - sub pages are indicated by 'a, b, c' and are marked on the preceding page by an arrow.The following themes have been selected:- length -unit of measurement meter- volume -unit of measurement litre (and connection to length meter)- mass -unit of measurement kg (as gravitational mass without reference to gravitation)The above extensive quantities will be examined in relation to:- time -unit of measurement seconds- temperature-unit of measurement degrees centigrade as examples of intensive quantity.

The use of "how much" for extensive and "how strong" for intensive quantity are unofficial and been 'invented' by Leif Johansen, a member of the Tewise group, to facilitate understanding of the concepts involved in the module.

Each theme is introduced with a page presenting a sense of feeling or qualitative impression. This opens the way for measurement, the use of a unit of measurement and of physical quantity. It's important to keep the historical dimension in mind, this being a good subject for pupil's independent work in the form of small projects with presentation in a different form.

Most of the pupil's work, though, takes place in groups.

Please remember that measurement of a physical quantity always has two parts: value unit of measurement


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Practical notes:

All the experiments are quite normal and there should be no problems with them. We have chosen to use digital (electronic) thermometers, thereby avoiding problems with mercury, should a thermometer break.

Some notes are, however, applicable to the experiment on page 1.15a :

You could use a 6 V 50 mA ( 300 mW) bulb which is 120 ohm at 6 V - the type often used as a rear stop light for bicycles. The resistor used could be of the PTC (resistance increases with temperature) or NTC (resistance decreases as temperature increases) type. These are also called thermistors. The value at ambient temperature should be 120 - 220 ohm, or nearly the same as the bulb. Using an PTC type avoids a "run away" situation. The light will dim with higher temperature.

Power supply can then at 12 V give normal light in the bulb and the changes can be seen when heating the resistor. Take care not to burn the resistor.


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1.01a

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How long is this room? What is the distance to the school from your home?How thick is this paper?We want to answer these types of questions, but how?

In olden times people had no rulers - but they had their feet.In your group everyone must measure the distance between two walls in your classroom using their feet.All the groups should use the distance between the same two walls in the room!

First everyone writes down their own results without telling anyone. Then write down the group's results in the table below:

Name of group member Length in 'feet'

1. Ask your teacher if you don't now to calculate the average.2. Did you all get the same results?3. Discuss in your group and write down the causes if you didn't all get the same

result.4. Make a table of all your results and calculate the mean average for the class. 5. Did anybody have the same measurement as the average?

Your group average:

Your class average :

remember always : number unit my pencil : 9,3 cm


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In olden days people often used their own bodies as instruments for measurement of distance. In this way they defined units of measurement from parts of the body.

1. In your group find which old units were based on parts of the human body. Use the library at your school. You can also use the Internet.

2. Make a poster showing your results - perhaps with a drawing of a human body.

3. Make a class exhibition of your posters.

4. Compare some of the units from different countries. Are they the same?

5. Why do we all now use the meter as a standard unit of measurement?

6. Find and read the story about the meter and the introduction of it in your country.

7. How many units (for longer and for shorter distances) do you know that are based on the meter. Use only units that are used today.

Study work for your group!

Subunit to meter How many meters (decimal number)?


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Now you are going to use the meter as a unit of measurement.Measure the length of a classroom with a ruler or with a tape measure.We can expect that everyone will get the same result.

You will need:- one or more rulers or a tape measure- paper and pencil

In your group measure the same distance as you measured with your feet on page 1.01a.

When you have finished, ask the other groups for their results and write all the results in the table below.

Group Result in meters Group Result in meters

Average result for your class:

Remember always: number unit

1. Did the other groups get the same result?2. Discuss in your group why there may be some differences - write your ideas down.3. Select one person from your group to form a group with one member from each of the other groups

where they can discuss any differences and come to a conclusion about the reasons for a difference.


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You have now measured "length". Length is a physical quantity. A physical quantity has a value and a unit. To be useful the unit must be well defined and recognized all over the world. That was the problem with feet, inches, phantoms and miles. There were different units from one country to another.

In your group find and write down the main points in the history of the "meter". Prepare a short presentation for the class.

Your teacher will choose one group make a presentation to the class.

A short "experiment":

Take a piece of string about 20 cm. long. Measure the length with your ruler.Cut the string into three pieces and measure the length of each piece.

Length of the string:

Length of piece 1 :

Length of piece 2 :

Length of piece 3 :

Add the three lengths:

Remember this!A physical quantity which can be added up when "things are put together" is a "how big" or, as scientists say, an "extensiv" quantity


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Things can be so small, that they are difficult to measure. The length of a cell in an onion or the thickness of a piece of paper can be difficult to find. You are now going to try and measure the thickness of paper!

You will need:your normal ruler, 10 small pieces of the same type of plywood or thick cardboard

Discuss and design an experiment to find the thickness of one just piece of plywood without measuring one piece. Your are allowed to find an average value of the thickness.

Your measurement for 10 pieces:

Your calculation:

Average thickness of 1 piece:

Discuss in your group. Could you use this method to measure the thickness of one page of a book or one piece of paper in a stack of papers?


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You measurement for (x) number of pages or pieces of paper :

Your calculation:

Average thickness of 1 pageor piece of paper:

Can you use the method from page 1.03a?Then let's do it!

You will need a paperback book or a stack of paper. You'll also need your normal ruler.

See if you can:

Can you use this method for thin wires?If yes then try it!

You can ask your teacher for a micrometer and ask him to show you how it works.

Measure the thickness of some wires.

Can you use the micrometer to measure the thickness of one sheet of paper?


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You can travel to Calcutta, but it would be quite a job to measure the distance with a ruler. And you can't even get to the star Sirius. How do we measure such long distances?

Two short stories about long distances:1. Distances on earth were and often still are measured by triangulation. You must have an instrument for measuring angles and a known distance between two points. The rest is simple mathematics,- just ask your math teacher. Perhaps you can do a calculation together! If you have two instruments for measuring angles, you can go from point1 to point2 and make then make the measurement.

In this way the distance to the moon, planets and the nearest stars can be measured. Sometimes the two points are two places on earth, but to measure the distance to the stars, you must make the measurement with the earth in two different places in space and with ½ year between the two measurements!

2. When an ambulance is passing by, you can hear the pitch of the siren falling when the ambulance is travelling away from you. The same thing happens with light. When a star is moving away from the earth, the 'pitch' of the light falls and the light from the star appears to be more red. This is an example of what is called "The Doppler effect".

Groups of stars called galaxies, at very long distances, are seen to be moving away from each other and to be moving quicker the greater the distance is. When a galaxy is moving away from us, the light from it will appear more red (redshift). The greater the distance the more red the light appears (and further toward infrared). From the 'pitch' of the light astronomers can calculate the distance to these very distant galaxies.

Later you will learn that looking over long distance in the universe is the same as looking back in time. The galaxies with a large redshift are also the oldest. In this way astronomers are actually able to look back to the beginning of the universe to a time close to "the Big Bang".

This page has no questions for you to answer. But I am sure you have a lot of questions after reading this page. In science we can't answer all questions right away and some questions don't have an answer yet, but perhaps you or some of your friends will find the missing answers if you become scientists.


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What do a bottle of Coke, a can of juice and a carton of milk all have in common? - Many things perhaps but one is - they all have an amount and a unit, the "liter".

You will need:- a measuring cylinder or a litre measure, some empty bottles, cans and cartons.

You will be checking the physical quantity "volume". On the empty containers you can find a value for the volume. Let's see if the producers cheat their customers.

You can try to find the real volume of the liquid in the container by measuring the volume.

Container type Producer writes ? Volume measured Difference

If you have a bottle having more than 1 liter, write down how you found the volume.

Is volume like length - a "How much" quantity? Put only one X!

Yes No

Hint - can you add volumes?

1. Did volume tell you anything about what sort of stuff you have?2. Which subunits of a liter do you know ?3. Can you find the volume of other containers - a cup, a vase and other things? If yes, then

do the measurement!4. Discus your answer about quantity with the other groups. Did you come to the same

answer?


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In your country are there other units for measuring volume - old ones?Remember : quantity is a number and a unit

1 .................. = ......... liter 1 liter = ..................... ............

1 .................. = ......... liter 1 liter = ..................... ............

1 .................. = ......... liter 1 liter = ..................... ............

1 .................. = ......... liter 1 liter = ..................... ............

1 .................. = ......... liter 1 liter = ..................... ............

1 .................. = ......... liter 1 liter = ..................... ............

Find the history of the "liter" and write down the main points of this story!


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You have seen that the physical quantity "volume" is used to measure liquids!Do solids also have volume?They take up space in the room, but can it be measured?

You will need:Some solid material - stone, wood, potato, pieces of metal or plastic - a measuring cylinder (250 or 500 ml), a long thin nail and water

All the pieces must be small enough that they can be put into the measuring cylinder.1.Fill water in the cylinder, but not to the top. Read and record the value of the volume.

2.Place the material to be measured completely under water (if it floats use the nail to push it down). Read and record the new value.

Material Volume before Volume after Volume of material

How did you find the volume of the material? Show one of the calculations.

1. Can a potato and a piece of wood have the same value for the volume?2. Can a potato and a drink of juice have the same value for the volume?3. In your group design an experiment which shows that the volume of a solid material is a

physical quantity of the type "how much"!


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In mathematics you have probably seen the use of cubic centimeters.Your mathematics teacher will also call this 'volume' - is science really so confusing?

A centicube is a little brick of plastic. All the edges are 1 cm long. Centicubes can be put together in the same way as "Lego".

Because the edges are all 1 cm long, each centicube is a cubic centimeter or 1 cm 3

You will need:Some centicubes, the same measuring cylinder as in 1.06a and water

Build a little block of centicubes. It must be small enough that it can fit in the measuring cylinder. Then measure the volume of some water ( in ml ) and then the volume of water and the centicubes just as you did on page 1.06a.

Do centicubes have a volume? .....................................

Number of centicubes Volume before Volume after Volume of centicubes ml ml ml

How many cm is your block of centicubes ? ...................................

Is there some connection between cm and the volume in ml ?

3

3

1. Go back to the history of the "liter" on page 1.05b and read it again!2. What sort of cube defined the liter?3. How many cm are there in a liter?4. How many liters are there in a m ?5. Discuss in your group - what do you prefer? liter, ml, hl ... or cm , dm , m ...

3

33 3 3


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In mathematics you have probably learned that you can find the volume of a square block by multipling the value of the height, width and depth. If you have a block that is 3 x 4 x 5 cm then it has a volume of 60 ml.

You remember that 1 cm = 1 ml !

You will need:Some blocks of wood, metal and plastik, a ruler or perhaps a vernier gauge.

The same measuring cylinder as on page1.05a and water

To use a vernier gauge you will need someinstructions from your teacher.

Measure the 3 edges (height, width and depth) of the different types of blocks, calculate the volume for each one and compare the results with measuring the volume in the cylinder.

Type of block calculated volume ml measured volume ml

3

If in your math class you have learned to calculate the volume of a cylinder, sphere and cone then you can try to compare your calculations with the volume that you can measure using this method.


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When it's windy, you can feel the air. You can fill your lungs with air and blow into a whistle.Does air have volume?

You will need:A measuring cylinderA large beaker of water.A tube.

What is the maximum volume of water the cylindercan have in it? ...........................

Now take the empty cylinder and look at it:

Is there anything in the cylinder? .............................................

Turn the cylinder upside down and press the opening under water in the beaker.

Is there something in the cylinder that stops the water from rising up? .........................

What is it ? ..........................................

Can you find the approxiamate volume of the air in the cylinder ? ........................................

With the cylinder out of the water, take the tube and place one end in the cylinder. Put the cylinder in the water againwith the other end of the tube above the water level. (See the diagram) Have someone suck on the end of the tube.

What happens to the volume of the air? ....................................................................................

1. Does air have a constant volume? (Tried to warm the cylinder with your hands)2. Do you know the names of any gases (air is a mixture of two gases)? ( Hint - fizzy drinks)3. Can you compress gas (air) to a smaller volume? Try !


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A strange experiment:

You will need:

Two measuring cylindersWaterCotton wool

Place the cotton wool loosely in one of the measuring cylinders. It should fill up to half of the measuring scale.

Fill the other cylinder half way up the scale with water.

Then pour the water into the cylinder with the cotton wool.

Record your measurement of the result.

In your group you must find some explanation for what happens when two the volumes are combined but don't add up to the total sum of their volumes. Write down the main points of your explanation.Hint : What is the volume of the air in the cotton wool - approxiamately?

cotton wool ml

water ml

cotton wool + water ml

Make a class poster where each group writes down their explanation!


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1.09a

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Have you ever gone shopping for potatoes?What sort of Physical Quantity and what sort of unit do they use in the shops?

The grocer uses a scales - often an electric or electronic. He will use a number value and a unit.

Take a look at some bags with flour, sugar, salt, washing powder and other goods. You will find the same unit - kg - for kilogram.

This physical quantity is called mass. It's measured in kilograms.

We use a scales for measuring mass. We will use a normal electronic kitchen scales.

1. Switch on the scales.2. Check for zero (display must show zero)3. Place a bag of goods on the scales4. Read the value from the display

NB - very often this value is shown with a - g - for gram. Gram is a subunit of kilogram where:1000g = 1 kg

Measure the mass of the different bags of goods and of other things you can find in your classroom.

1. Try the library or the internet to find the history of the "kilogram".2. Find subunits to the kilogram that are smaller and bigger than grams.3. Can you think of any older units for the mass? Write a short story about these units and about

how they were used.


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Why are scientists so difficult to understand?

If you ask the grocer, she will not talk about the mass of potatoes. She will say that she weighs the potatoes. Your mother will also talk about the weight of the flour in a cake.It is normal in everyday life to talk about the weight of things. Even the scientist when he is outsidehis lab will refer to weight.

But when he is in his lab or your physics teacher is in her classroom with you, they will useproper scientific language. In scientific language we say we are finding the mass of an object.Weight is actually something different - another physical quantity where the unit - Newton - isused. This value can be measured using a Newton meter or in other ways.

When people say they are weighing or finding the weight of something, and they find how many kilograms it is, then they are really finding the mass. They just don't realize it. Scales are calibrated to show mass.

The mass of a bag of sugar tells you how much sugar you have. If you go to another place on the earth you will still have the same amount of sugar. If you were lucky enough to get a trip to the Moon and you took the sugar with you, you would still have the same amount of sugar.But if you also took the scales with you, you would see that the scales show a different value. On the moon the scales that are calibrated to show 1 kg on earth would only show 0.167 kg for the same amount of sugar.

To use the scales on the moon to control the 1 kg mass of your sugar you would need an exact copy of the 1 kg weight from Paris. 1. Place the copy on the scales on the moon 2. Write down the number (it's much smaller than 1 kg and closer to 0.167 kg)3. Now put the bag of sugar on the scale.4. Compare to two numbers on the scales (the two values should be the same if the grocer hasn't

cheated her customers!)

A long history!


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How can we work with scales?Liquid or sand - the same problem!

You will need:A kitchen scales, some dry beakers, water and some sand

When you find the mass of a bag of sugar, you find the brutto mass (bag + sugar). The mass of the sugar is called the netto mass. The mass of the bag is called the tara mass.

Brutto mass = tara mass + netto mass

Normally, we are only interested in the netto mass - the mass of the sugar or of the quantity we are measuring.

Always zero the scales first.

You will now measure 0.750 kg of water.

1. Place a beaker on the scales.2. Press the Tara or Zero button to zero the scales.3. Pour water in the beaker until the scales show 0.750 kg

If you have an older scales that won't let you zero with the beaker on the scales, then:

1. Find the mass of the beaker - this is the tara mass - by placing the empty beaker on the scales.2. Calculate the brutto mass by adding the mass of the beaker and 0.750 kg together.3. Pour water into the beaker until the scales show the brutto mass value.

Use this same method to measure 200 g of sand.

This was only an exercise in using the scales. You will need to practice some more before you are qualified in using the scales.


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Mass is difficult to understand, particularly when the science teacher is trying to explain it to you!But what sort of physical quantity is mass?

You will need:A kitchen scales, some dry beakers all of the same size, water, sand and salt.1.Pour a quantity of water into each of two beakers. Measure the mass of each one with the scales.Record the result in the table below. Then pour these together into one beaker. Measure and write down the result.

quantity 1 mass kg quantity 2 mass kg together mass kg




2.In the same way, make one quantity of sand and one of salt in each beaker. Measure and record each one. Then pour these together into one beaker. Measure and record the result.

3.Now make one quantity of sand and one of water in each beaker. Measure and record. Then pour these together into one beaker. Measure and record the result.

4.Make one quantity of water and a small quantity of salt in each beaker. Measure and record. Then pour these together into one beaker. Mix until the salt is dissolved. Measure and record the result.

1. Can you find something the 4 experiments all have in common?2. What is special about experiment 4?3. Is mass a physical quantity with the characteristic of "how much" (extensive quantity)?4. If you had done the 4 experiments and then measured the volumes, you would have seen

different results. (You are welcome to try it) - In what way would the results be different?


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We all use clocks and watches. We all measure time.Time is a Physical Quantity- but what a quantity!Have you thought about time - sometimes?

You and all your friends in the class are sitting at your tables. Watches and cell phones with clocks should be placed out of view - in your pocket or in your school bag. If there is a clock in the classroom, this must also be hidden.

On the table in front of you, you should have a pencil and piece of paper.

Only your teacher has access to a clock or watch.

1.Everyone should be quiet and look at the teacher. She will raise her hand and when she does you must try to find out how many seconds, minutes or hours goes by before she lowers her hand again.

I'm sure it took:........................................................................................

2.Now the teacher will read a very funny short story. You now have to guess how many seconds, minutes or hours it took to read the story.

I'm sure it took: ...........................................................................................

1. Did you have the same feeling for time in both cases?2. Make two statistical histograms for everyones guesses, one for each case and

then calculate the average in both cases. Mark these on the histograms.3. Compare this average with the real values from your teacher.


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Time is difficult to estimate, we don't have a natural clock in our bodies (your pulse is unstable and changes with time).

We can only go forward in time, but we can think and calculate backwards. It's only in science-fiction that you can travel back in time.

You don't know what's going to happen in the next minute, but you can influence what happens. You know what happened in the minute that just passed, but you can't change it.

Human beings have always tried to measure time. For them night and day, themovement of the moon with its changing phases, the "movement" of the sun and thechanges during the year were the basis for the measurement of time. Later peoplealso needed shorter units of time and they created hours, minutes and seconds.

Here are some themes for project work in groups. Prepare a lecture for your class. You can illustrate your presentation with posters or a computer presentation.

1.Find the history of the units of time and especially why we have the odd conversions between the units.

2.Now we use seconds as a basis for measurement of the physical quantity of time.Find the history of the second, the changing definitions and the use of the mean second.

3.In olden times each town measured time based on the movement of the sun. Now we have mean time. Please describe this concept and also tell why clocks don't show the same time all over the world.

4.Navigation in olden times was difficult. Sailors in the 15th and 16th centuries could easy findhow far they were from the Equator - their degree of latitude between Equator and the Pole.But the problem was finding the distance around the globe (degree of longitude).Explain why this was such a problem and why the invention of the chronometer (very exact clock) helped to solve the problem.

We all use clocks and watches. They must be as exact as possible.Many clocks and watches use a common technique!

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1.13a

Project Tewise


You will need:A lab stand with accessoriesA stopwatchSome weightsSome string

Definitions:An oscillation is a movement of the weight from the outmost point on one side to the other side and back again.

Oscillation time is the time for one oscillation

Amplitude is the length (correct angle) from the vertical point in the centre to the outmost point in the oscillation.

Pendulum length is the distance from suspension point to centre of the weight.

The best method to find the oscillation time is to measure the time taken to complete 10 oscillations and then find the average time for one oscillation.

In designing an experiment we must always remember to only change one parameter when going from one part of the experiment to the next part.

Now your group will do an experiment to show which circumstances can have influence on the oscillation time and which have no influence.

You can use the template on 1.13b

1. Why is a pendulum a good construction for a clock or watch?2. Try to find some clocks and watches where you can have a look inside.3. Many electronic watches don't have a mechanical pendulum. Do they have

another sort of pendulum (ask a watchmaker)?


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1.13b

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Conclusion:

Length m mass kg amplitude time for 10 osc. sec time for 1 osc. sec


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Is it warm or cold? Can you feel it?The human body can feel warmth and cold. You have nerves that sense heatin your skin. Can you estimate the temperature?

You will now play two old physics games.1.You need three beakers. One with ice cold water, one with normal tap water and one with warm water (not too hot!) from the hot water tap.

Place your hands in two of the beakers. Which hand senses cold, which senses warmth?

Did you all have the same experience?

2.You need three surfaces - one of wood, one of plastic and one of metal.

Put one hand in turn on the different surfaces.Do you have the same sense of temperaturefrom all of the surfaces?

Take a piece of paper and put it on the metal surface. Feel the temperature. Then put your hand back on the surface. Did you sense a change?

1. Can we rely on our senses?2. Why do people have senses and nerves for warmth and cold?3. What kind of instrument do we need for measurement of a physical quantity

with connection to warm/cold (temperature)?


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1.15a

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The instrument is, of course, a thermometer.But there are several types of termometers.What are the physics principles behind termometers?

You will need:Two beakers each with a rubber stopper and a glass tube in the stopperA piece of bimetal 10 cm longA wooden clothespeg Electrical leads, a special resistor, 6 V 50 mA bulb with socketA power supplySome coloured waterPaper for making notes.

1.Take a beaker filled with only with air and place the stopper in the beaker with a drop of coloured water in the glass tube.- Warm the beaker with your hand. What happens?- Put the beaker under the cold water tap so that water runs over the

outside. Make a note of what happens.

2.Take a beaker filled with coloured water so the glass tube is also filled halfway up.- Do the same things as in #1. Perhaps you should also try heating

gently with a gas burner. What happens?

3.Take the piece of bimetal and hold it with the clothespeg above the flame from the burner so that it is gently heated. What happens?

4.Connect an electrical circuit according to the diagram and turn on the power supply. Gently heat the resistor (but not too much!) What happens?

1. Nearly all things solid, liquid or gas expand when heated. Do you have any experience with this from your everyday life?

2. There is an exception with water. In your group try to find information about this by using the library, internet or by asking your teacher.

3. Why is this exception important for the earth? In your group try to find the answer.


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Temperature is a physical quantity and the unit is the degree. But there are several temperature scales that use the degree. The celcius or centigrade scale starts at 0 C at which temperature ice melts and turns to water. At 100 C water boils and turns to steam. There are 100 equal steps in the value between ice melting and water boiling. Each one of these steps is one degree. Centigrade is the first unit we meet which can have negative values. The values can also be more than 100 C . Normally our thermometers are calibrated in centigrade.

The Kelvin scale is used by scientists. In the Kelvin scale the degrees are the same size as in the centigrade scale. There are 100 K between the melting point of ice and the boiling point of water but the zero value in the Kelvin scale - 0 K - is minus 273 C . This is also the lowest temperature that can exist. Using the Kelvin scale means that the melting point of ice is 273 K and water's boiling point is 373 K .

In the USA and some other countries they use another scale - degrees of Fahrenheit - but only for everyday life. This scale is of no importance in science - so please forget it. I am sure your math teacher would enjoy giving you problems where you convert degrees from one scale to another.

Ordinary thermometers use expanding liquid. Inexpensive thermometers use coloured alcohol where good quality thermometers use mercury (liquid metal). But if a mercury thermometer is broken the vapour from the mercury is a very dangerous poison.So instead we prefer to use modern electronic thermometers in the schools. They all in one way or another use the same principle as in example 3 on page 1.15a.

A story of degrees and thermometers

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If your group has plenty of time you could study the history of thermometers, the measurement of temperature and the different units.


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We're all interested in variations in temperature, especially when it's the weather. Have you ever made a graph showing changes in temperature over time?

You will need:A thermometer frozen inside an ice cube A beaker (it could be used to freeze the water with the thermometer in it)A gas burner, tripod, ceramic gauzeA stopwatch

You will need at table showing:

with room for about 30 measurements.

Take the ice cube with the thermometer out of the freezer.Place it in the beaker and light the burner underneath the ceramic gauze (see diagram). At the same time, start the stop watch and record the temperature. Take a measurement of the temperature after each minute. If you have a small lump of ice then perhaps after each half minute.The ice will melt and then the water will boil.After boiling the water for several minutes, turn off the burner and let the glass cool down.

Make a graph - showing the change in temperature over time. You should have time (minutes) for the x- axis and temperature in centigrade for the y- axis.

You can use the graph paper on page 1.16b

Time in minutes Temperature centigrade

1. Discuss the results and the graph line.2. Can you find explanations for when the temperture doesn't change?3. The burning gas is transferring energy to the water. Explain what is

happening at the various stages in the graph.


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1 kg of sugar mixed with 2 kg of salt gives a mass of 3 kg. This is an example of "how much".But what happens with the physical quantity "temperature"?

You will need:- four beakers of different sizes- a measuring cylinder- water from the cold and hot tap- an electronic thermometer1.Fill beaker A half full with water that is about 21 C. Measure and record the temperature. Pour 1/3 of the water into beaker B and the rest into C. Measure the temperatur in B and C.

2.Fill cold water in beaker D (about 15 C) and warm water in beaker E (about 35 C ). Measure and record the temperatures. Pour both into beaker F. Measure the temperature.

Can you add temperature?

A temp C B temp C C temp C

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Can you divide temperature?

D temp C E temp C F temp C o o o

1. Does temperature have the same property as physical quantities like mass, length and volume? Try to find an answer in your group.

2. If you have 100 ml water at a temperature of 80 C and then pour 10 ml of the water into a smaller beaker. What temperature do you expect to measure for the water in the small beaker.

3. If the temperature was 74 C , can you explain why?

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Temperature is a physical quantity and the unit of measurement is the degree in one form or another. This quantity has other properties than mass, volume and length. They are all extensive quantities, which we also called "how much" quantities.

They can be added and they can be divided. They tell us something about the quantity of matter.

Temperature can't be added or divided. Temperature is the same for big or small quantities. Temperature tells us something about the quality of matter.

Such a physical quantity is call an intensive quantity or a "how strong" quantity.

Temperature is a intensive - "how strong" - physical quantity.

You will later learn about other "how strong" quantities. Here are some new words.

Density as mass in relation to the volume.Pressure as force in relation to the area.Specific heat as internal energy change in relation to the mass....

To understand specific heat you can try a small experiment as a first experience with another "how strong" quantity.

A new physical quantity with new properties


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You will need:2 tripods with ceramic gauze 2 beakers 250 ml - 300 ml1 100 g brass weightwater1 measuring cylinder1 digital thermometer1 gas burner1 stop watch

In one beaker put the 100 g brass weight and 100 ml (100 g) of water. In the other beaker place 200 ml ( 200 g ) of water. The water should be around 20 C.

Heat both beakers until the water reaches 80 C . Measure the amount of time it takes to reach 80 C for each beaker. You start the stopwatch when you start heating and stop the watch at 80 C .

Did you have an explanation for what happened?

200 g water sec.

100 g water + 100 g brass sec.

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comeniusproject tewise measurement and physical quantities · "measurement and physical...

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