MODULE mod7A mod7B mod7C mod7D mod7E mod7F mod7G mod7H mod7I mod7J mod7K mod7L mod8A mod8B mod8C mod8D mod8E mod8F mod8G mod8H mod8I mod8J mod8K mod8L mod9A mod9B mod9C mod9D mod9E mod9F mod9G mod9H mod9I mod9J mod9K mod9L 7ga1
7Ga/1 Observation sheet
Name _____________________________ Class ____________
Observations
Solid
Liquid
Gas
A Is the shape fixed or can it change?
B Does it flow?
C Is it easy to squash?
D Can you change its volume?
E Does it feel heavy or light?
[ observing ]
7Ga/2 Properties cards
Solids
Liquids
Gases
Difficult to squash
Flow easily
Do not flow
Easy to squash
Fixed shape
Fixed volume
High density
No fixed volume
Low density
No fixed shape
Quite high density
[ knowledge ]
7Ga/3 Solid, liquid or gas?
Cut out the cards below. Arrange them into three piles - one for solids, one for liquids and one for gases. You will need to think carefully about some of them. Your teacher may ask you to explain why you put things in a certain pile.
---------------------------------------------------------------------------------------------------------
air
water
concrete
rubber
jelly
sugar
hot custard
jam
honey
metal
paper
steam
pencil
foam rubber
tomato sauce
sand
toothpaste
cold custard
Plasticine
stone
[ considering ]
7Ga/4 Properties summary
1 Fill in the gaps in these sentences, using words from the box. You may need to use some words more than once.
dense
density
easy
fill
fixed
flow
lower
properties
rise
squashed
volume
All solids have some things in common. These are called the _____________________ of
solids. Solids have a _____________________ volume. They cannot be
_____________________.
They also have a _____________________ shape which cannot be changed, making them
ideal materials to use to build large structures such as bridges. They do not
_____________________ and so they cannot be poured.
Solids also have a high _____________________ , which means that their mass is higher than
the same _____________________ of other materials. Like solids, liquids cannot be
_____________________ .
They have a _____________________ which is fixed. However, they are different from solids
because they can _____________________ quite easily and have no
_____________________ shape. This means that they always take the shape of the container
they are placed in. Although liquids are _____________________ , they usually have a
_____________________ density than solids.
Gases are quite _____________________ to squash and so they have no fixed
_____________________. They also have no _____________________ shape. They will
spread out and _____________________ any shaped container. Gases are less
_____________________than liquids (which is why bubbles _____________________ in a
fizzy drink).
[ literacy, knowledge ]
7Ga/5 Solid or liquid?
Some substances have properties which make it difficult for us to decide whether they are really solids or liquids. Sand is a good example.
If you look at individual grains of sand, you can see that they have definite shapes. Each grain is very hard, and keeps its shape. You can make wet sand into a sand castle.
But if you have a bucket full of dry sand, you can pour it. The ability to flow is a property of liquids but not solids, so sand appears to have the properties of both.
1 Write down all the reasons why you might think sand is a solid.
2 Why might we also think that sand is a liquid?
Choose one of the following materials:
custard
bread dough
3 Imagine you are writing to a friend. Describe the material, without mentioning its name, so that your friend can guess what the material is.
4 Is the material a solid or a liquid?
a Write down all the reasons for thinking it is a solid.
b Write down all the reasons for thinking it is a liquid.
c Can it change? For instance, is custard always runny? How can you make it change?
5 Now answer questions 3 and 4 again for one of the other materials.
[ knowledge, literacy ]
7Ga/6 Hot and runny!
Asif, Sue and Jo each did an experiment to find out if oil got runnier when it was hot. This is the apparatus that they used.
These are the results that they got.
Temperature (°C)
Time for oil to run through funnel (seconds)
Asif's results
Sue's results
Jo's results
22
138
124
132
30
55
52
57
40
35
33
36
50
25
24
27
60
23
21
70
20
19
80
18
1 If you had to do this experiment, describe what you would do. You should write three or four sentences.
2 Their experiment was a fair test. What did they keep the same each time?
3 Why do you think their coolest temperature was 22 °C instead of 20 °C?
4 Work out the average time for each temperature, and put your answers in a table like this:
Work out the average by adding all three results together, and then dividing by 3. Write your answers to one decimal place.
5 Plot a graph of the results. Use axes like this:
Draw a smooth line through the points on your graph.
6 Was the oil runniest at 80 °C or 22 °C?
7 Write a conclusion for this experiment that describes what Asif, Sue and Jo have found out.
[ considering, presenting, numeracy ]
7Ga/7 Mercury - a special liquid
Mercury is a special metal. It conducts heat and electricity like other metals, but it is the only metal that is liquid at room temperature.
Mercury is also very dense. (1 cm3 of mercury is much heavier than 1 cm3 of most other metals.)
The special properties of mercury mean that it can be used to make things that need something that will flow, but which also behaves like a metal.
Research
- Find out two or three uses of mercury.
- For each use, find out why mercury was chosen for the job.
- Are there any dangers from using mercury?
- When you have gathered your information, produce a leaflet or poster display to tell other people about mercury.
[ research, literacy ]
7Gb/1 Dilution 1
Apparatus
- Test tube rack
- Eye protection
- Five boiling tubes
- Purple liquid
- Pipette
The purple dye in this experiment will stain if you get it on your hands. Be careful, and make sure you are wearing eye protection.
Method
1 Pour the purple liquid into a boiling tube so that it is about half full.
2 Write down the colour of the liquid in the table.
3 Use the dropper to put 10 drops of the liquid into the second boiling tube.
4 Half fill this second tube with water.
5 Look at the tube. What colour is the liquid? Write it in the table.
6 Now take 10 drops from this tube and put it into tube 3.
7 Fill this tube half full with water.
8 Repeat steps 6 and 7 until you can't see the colour any more. When the colour is very pale, you may see it better by looking down the tube. It may help to put a piece of white paper under the tube.
Recording your results
Tube number
Colour
1
2
3
4
5
6
Considering your results/conclusions
How many tubes did you use before the colour disappeared? _______________________________
In the last tube, is there any of the purple chemical left? ___________________________________
The purple chemical is poisonous. If you had used drinking water and clean tubes, do you think it would be safe to drink the water in the last tube? Explain your reasons.
________________________________________________________________________________
[ observing, considering ]
7Gb/2 Dilution 2
- Potassium manganate solution
1 Draw a table in your book with the following headings. You should leave space for at least five tubes.
2 Measure out 10 cm3 of potassium manganate solution into a boiling tube.
3 Write down the colour of the liquid in the table.
4 The purple solution was made with 1 g of potassium manganate in every litre (1000 cm3). We can divide by 10 to find the mass there would be in 100 cm3. This comes to 0.1 g. Now divide by 10 again to find out how much there would be in 10 cm3. Write this figure in the third column of your table.
5 Use the measuring cylinder to transfer 1 cm3 of the liquid from tube 1 into the second boiling tube. What mass of dye is in tube number 2? Write this figure into your table.
6 Fill this second tube with another 9 cm3 of water to make 10 cm3 in total.
7 Look at the tube. What colour is the liquid? Write it in the table.
8 Now repeat steps 5 to 7, putting the liquid from tube 2 into tube 3. Write your results in the table
9 Keep diluting the dye until you can't see the colour any more. When the colour is very pale, you may see it better by looking down the tube.
1 How many tubes did you use before the colour disappeared?
2 What is the smallest mass of dye that you could still see?
3 Is there any dye at all in the last tube? If so, how much?
4 Potassium manganate is poisonous. If you had used drinking water and clean tubes, do you think it would be safe to drink the water in the last tube? Explain your reasons.
7Gb/3 The missing lunch mystery
The Mystery
Melissa's cheese sandwich has gone missing. Who took it?
Barrett Holmes, ace detective, is on the case.
Melissa left her bag in the classroom at break. After break, all the things in it were mixed up.
Judy saw Ben in the classroom at break.
Judy thinks that Ben took Melissa's sandwich.
Chris does not buy much for lunch - he says he isn't hungry.
Barrett thinks that whoever took the sandwich will eat it straight away.
Barrett thinks the thief will not be able to eat much at lunchtime.
The next morning there is a funny smell coming from behind the radiator in the classroom.
Chris does not come to school the next day. His mum phones to say he has a sore throat.
That afternoon, Ben hands his science homework in on time. The first time ever!
7Gb/4 Swift ideas
Gilbert White was born in a village in Hampshire in 1720. He was very interested in watching birds and animals. One of his favourite birds was the swift.
He never saw swifts in the winter. Nobody knew what happened to them. Some people thought that they migrated (flew south to warmer countries). Other people thought that they hibernated (went to sleep for the winter).
Gilbert White wanted to know which idea was true. He thought that if the swifts hibernated, he should be able to find them asleep in holes. He looked in lots of holes during the winter. He even hired some men to look in all the bushes near his village, to see if they could find any sleeping birds. No-one could find any swifts.
Today we know that swifts migrate to South Africa in the winter. People in South Africa see the swifts. In Gilbert White's time there were no telephones, so he could not phone someone in South Africa and ask them if they had seen the birds.
1 Read the passage carefully.
a Draw a circle around all the phrases that are observations.
b Draw a straight line under all the phrases that are theories.
c Draw a wriggly line (~~~~~~~~~~) under all the phrases that are predictions.
d Draw a box () around all the phrases that show Gilbert White testing his predictions.
2 Do swifts migrate or hibernate in the winter?
___________________________________________________________________________
3 Why couldn't Gilbert White ask people in other countries if they had seen the swifts?
7Gb/5 Proving nothing! 1
In Italy, 350 years ago, some scientists did experiments with air and water. They had a long tube like this.
When they opened the tap at the bottom, some of the water fell out, but most of it stayed in. There was a gap at the top. No air could get in, so they thought that this was a vacuum (a place with no air or anything else in it).
When they undid the lid, they could hear a hissing sound as air rushed in.
The scientists changed the tube and put a bell in the top. Sound needs a substance to travel through. They thought that if there was no air there, they would not be able to hear the bell. When they had made a gap at the top, they used a magnet to move the bell and make it ring. They heard it ring.
Torricelli thought that their experiment had not been a very good one. Sound can travel through solids, and the bell was hanging on a solid bar which was attached to the glass. They had not proved anything at all! He decided to do some experiments of his own.
1 The phrases in italics are observations, theories or predictions.
b Draw a straight line under the phrases that are theories.
c Draw a wriggly line (~~~~~~~~~~) under the phrases that are predictions.
2 Why did the scientists think they should not be able to hear the bell?
3 Why did Torricelli think that they had heard the bell?
4 Why did Torricelli decide to do his own experiments?
7Gb/6 Proving nothing! 2
A vacuum is an empty space with nothing in it. The ancient Greeks thought that a vacuum could not exist.
Galileo (1564-1642) was a famous scientist who lived in Italy. He thought that a vacuum could exist, but said that the big problem would be proving that you had made a vacuum.
Evangelista Torricelli (1608-1647) had worked with Galileo, and after Galileo died in 1642 he started to think about the problem of the vacuum. Some friends of Torricelli in Rome were doing some experiments with tubes of water. They thought that if they had a long enough tube, they could make a vacuum. They made a long lead tube with a strong glass flask at the top. The bottom of the tube was put into a barrel of water. It had a tap at the bottom.
They filled the tube and the flask with water and sealed the top. Then someone at the bottom opened the tap. The level of the water fell until the column of water was about 10 metres high. There was a space at the top. No air could get in, and they thought they had made a vacuum. How could they prove it?
If they opened the flask at the top there was a hissing sound as air rushed in. That seemed to show that there had been nothing there before.
They tried another experiment with their tube. They hung a bell inside the flask at the top, filled the whole thing with water and opened the tap at the bottom. They got their space, just like before. Someone leaned out and used a magnet to move the bell and make it ring. They thought that if there was a vacuum, they should not be able to hear the bell because there was no air for the sound to travel through. But they heard it ring!
But sound can travel through solids, and the bell was hanging on a solid bar which was attached to the glass. Perhaps this had not been a very good way to show that the space in the tube was a vacuum.
Torricelli decided to do his own experiments. He thought that the water stayed up in the tube because of the weight of air pushing on the liquid in the tank. He predicted that if he did the same experiment with mercury, the weight of air could not hold up as much of it. His prediction was right, and when he set up his tube the mercury fell out until there was only about 76 cm of it. However this did not help to prove that the space at the top was a vacuum.
A French scientist called Blaise Pascal (1623-1662) heard about Torricelli's experiment. He decided to do some more experiments to prove that there was a vacuum above the mercury in Torricelli's tube.
He made some apparatus like this:
The mercury in the little tube would not stay up. Pascal said that this was because there was no air pushing down on the rest of the mercury. When he let air into the top of the large tube the mercury rose up in the little tube.
1 What did the ancient Greeks think about vacuums?
2 What did Galileo think would be the problem with a vacuum?
3 Write down the sentences in the text that describe
a theories b predictions c observations.
4 How did Torricelli's friends first try to show that they had made a vacuum?
5 They tried to prove they had made a vacuum using a bell.
a What did they predict would happen if they had made a vacuum?
b What actually happened?
6 If an experiment does not give the result you expect, it is because your idea was wrong, or there was something wrong with the experiment. Which of these is true for the bell experiment? Explain your answer.
7 In Pascal's experiment, why didn't the mercury stay up in the little tube when there was a vacuum at the top?
8 Why do you think Pascal did his experiments with mercury instead of water?
7Gb/7 A weighty matter
If you fill a test tube full of water, and put it upside down into a beaker, the water stays in the test tube. Why does this happen?
Galileo knew that air had weight. He had weighed a flask of air, and then pumped more air in and weighed it again. It was heavier when it had more air in it, so air must have had weight.
Torricelli had worked with Galileo, and he used the idea of air having weight to explain why water stayed up in tubes. He said it was the weight of air pressing down on the water in the tank at the bottom that held it up. The weight of the air was only enough to hold up about 10 metres of water in the tube. If your tube was longer than this, you would get a vacuum at the top. A tube full of liquid set up like this is called a barometer.
NOT TO SCALE:
The height of the water under the vacuum should be over 10m high!
Torricelli did the same experiment with mercury. Mercury is a very dense liquid, so the weight of the air would not be able to hold up as much of it. Torricelli predicted that the air could only hold up about 76 cm of mercury. When he tried his experiment he was right! He had used his ideas to make a prediction, and he had tested his prediction.
Many people did not believe this explanation. Some people thought that it was a pull from the vacuum at the top of the tube that held up the water or mercury.
Blaise Pascal did a lot of experiments with air and vacuums. He agreed with Torricelli's idea that it was the weight of air on the liquid at the bottom that held up the liquid in the barometer tube. He predicted that if he took his barometer up a mountain then the length of the liquid in the tube would get less, because there was less air above to push down.
Pascal was not well enough to climb a mountain, so his brother-in-law (Perier) did the experiment for him. Perier had two barometers. He set up one at the bottom of the mountain, and left someone with it who would measure the mercury while he was gone. He carried the other barometer up the mountain, and set it up at different places. Sure enough, at the top of the mountain the mercury was nearly 8 cm shorter than it had been at the bottom. When he got back down, the people who had stayed at the bottom told him that the mercury there had not changed all day.
1 How did Galileo know that air had weight?
2 Why did Torricelli think that water stayed up in tubes?
3 What happens to a tube of water if it is longer than 10 metres?
4 Why is the height of mercury in a tube less than the height of water?
5 In science, people try to prove their ideas by making a prediction, and then doing an experiment to see if there prediction is correct.
a What is the idea that Torricelli and Pascal were testing?
b What prediction did Torricelli make?
c How did he test his prediction?
d What prediction did Pascal make?
e How did he test his prediction?
f Was his prediction correct?
6 Why do you think Perier left a barometer at the bottom of the mountain?
7Gc/1 The story of Robert Brown 1
Robert Brown was a Scottish scientist who studied botany - the science of plants.
One day in 1827, he was using his microscope to look at some pollen grains that were floating in water. To his surprise, he noticed that the pollen grains were moving in a strange, zigzag way. He checked his observations carefully and found that they were correct.
He knew that pollen came from living plants. He thought at first that the pollen itself might be alive, and capable of moving on its own. He tried the experiment again, but instead of pollen he used something that he knew definitely couldn't be alive. The zigzag motion was still there! This really baffled Brown, who reported his results, but could not explain why the pollen moved in this way. The experiment was then forgotten as no-one could come up with a convincing explanation.
Nearly eighty years later, in 1905, Albert Einstein came up with a theory to explain Brown's observations. He suggested that the pollen grains were being bombarded on all sides by water particles. The water particles were too small to be seen. The effect of lots of the water particles added together was just enough to push the pollen grains around.
In 1908, Jean-Baptiste Perrin used Einstein's theory to calculate the size of a water particles. This estimate suggested that water particles were less than 0.000 000 001 metres (10-9 m) in size.
1 Collect the set of pictures on Worksheet 7Gc/2 and cut them out. Put them in the correct order so that they tell the story and stick them in your book.
2 Which frame or frames in the story show scientists:
a making predictions
b planning experiments
c making observations
d drawing conclusions and thinking of theories?
3 Which scientist first made the observations of the moving pollen grains?
4 Who successfully explained the observations?
5 How many years were there between the observations and the conclusion?
6 What was Robert Brown's first explanation for the movement of the pollen grains?
7 Suggest something that was non-living and in very small grains that Brown might have used to check his ideas.
8 Scientists knew that bacteria could be found in water. How could you plan an experiment to show whether bacteria were responsible for moving the pollen grains around?
7Gc/2 The story of Robert Brown 2
A
B
C
D
E
F
G
H
7Gc/3 Summing up states 1
There are three states of matter: _______________ , _______________ , and _______________ .
Shape
Have a ____________
shape
Have no ____________
____________
Have no fixed
Volume
Density
Are usually ____________
dense than solids
Have a very low
Ability to flow
Do _____________ flow
____________ quite
easily
____________ very
Ability to be squashed
_____________ be
____________ to squash
Quite easy to
Closeness of particles
Particles are very
_____________ together.
They can hardly
_____________ at all
Particles are quite t
They can
_____________ past each
other
Particles are ____________
out and free to
____________ around
Use these spaces to
draw diagrams to show
how the particles are
arranged
Examples
7Gc/4 Summing up states 2
Complete each space in the table.
Property
Use these spaces to draw diagrams to show how the particles are arranged
7Gc/5 Using ideas about particles
Scientists can use their imagination to make models of the way they think that particles are arranged and the way that they move. These models can explain the observations that we make, and can sometimes be used to make further predictions.
1 Cut out all the boxes.
Think about which of the 'theory' boxes best matches each observation.
Then look at the 'particle model' boxes and find the correct diagram.
When you have matched up the six sets correctly, stick them into your book.
2 Use the information in the boxes to make the following predictions. In each case, explain your reasoning. If you cannot make a prediction, try to explain why not.
a What happens to the size of a solid if you heat it?
b What happens to the size of a solid if you cool it down?
c Which evaporates the fastest, petrol or perfume?
d What will happen to the temperature of the ice while it is melting?
--------------------------------------------------------------------------------------------------------
A When water boils, it stays at the same temperature as long as there is some water left.
B Ice is a solid which floats on water. Snowflakes are always six-sided shapes.
C If you spill some petrol, it evaporates very quickly. Water takes longer to evaporate.
When the water boils, the heat gives the particles enough energy to escape from the liquid.
E When ice melts, it takes up less space.
F When you heat water, it expands (gets bigger).
DO not make a double sided photocopy of this worksheet
Theories
1 In ice there is a regular arrangement of particles. The particles build up in hexagon rings. This explains the shape of snowflakes. There are gaps in the middle of the rings, which means that ice is less dense than water.
2 Hot water takes up more space than the same amount of cold water. In any volume, there will be fewer particles of hot water than cold.
3 The bonds between particles of petrol are weaker than the bonds between particles of water. It is easier for the petrol particles to escape from the liquid and evaporate into the air.
4 When the water boils, the heat gives the particles enough energy to escape from the liquid.
5 As the water heats up, the particles gain energy and move faster. This movement means that the water takes up more space.
6 When the ice melts, the hexagon pattern is broken up. The particles do not have any particular arrangement, and there are fewer gaps between them.
Particle models
7Gd/1 Observing diffusion in liquids 1
In this experiment you will look at the way that colours spread through a liquid. You will need to choose something that gives a strong colour when it is put in water. You might be asked to do this experiment at home, in which case you might use:
- a spoonful of Marmite or Bovril
- a stock cube
- a teabag
- some food colouring with a small dropper.
1 Collect two glasses. Fill one with hot water from the tap, and the other with cold water.
2 Leave the water to stand for a minute or two so that it has stopped moving.
3 Carefully put your coloured substance at the bottom of the glass. Make sure you do not stir the water.
4 Leave the glasses of water absolutely still. Make a note of the time.
5 Draw a diagram of each glass to show what it was like just after you put the coloured substance in the glass.
6 Look at the glasses again after 10 minutes. How far has the colour spread through the water? Draw another set of diagrams to show what has happened.
7 Draw a third set of diagrams to show what has happened after 30 minutes.
Copy and complete these sentences.
The longer you leave the water, the more the colour _______________________.
The hotter the water, the _______________________ the colour spreads out.
This is because in hot water the particles are moving ______________________ than in cold water.
7Gd/2 Observing diffusion in liquids 2
In this experiment you will investigate the speed of diffusion through a liquid. You might be asked to do this experiment at home.
- Clock or watch
- Ruler
- Some glasses
If you are doing this experiment at home, check with your parents and be very careful if you plan to use boiling water from a kettle.
Many types of glass may crack if you put boiling water into them. If in doubt, do not use boiling water.
You will also need to choose something that gives a strong colour when it is put in water. If you are doing this experiment at home you might use:
Planning
1 You are going to compare the speed of diffusion at a number of different temperatures.
2 How many different temperatures will you try?
3 Can you measure the temperature, or will you just describe it (e.g. cold, warm, hot)?
Prediction
4 How do you think the temperature will affect the speed of diffusion?
5 Explain your ideas using particle theory if you can.
1 Collect your glasses. Fill them with water at the correct temperatures for your plan.
5 Look at the glasses again after 2 minutes. How far has the colour spread through the water? Measure the distance with a ruler.
6 Take measurements every 2 minutes. Stop when the colour has spread all the way through the water, or after about 20 minutes.
Considering your results/conclusion
6 Plot a graph of the distance travelled by the colour against the time. Use axes like these.
7 Show each different temperature with a different colour.
8 Use your graph or your table to work out at which temperature the colour diffused the fastest.
9 Describe how changing the temperature affects the speed of diffusion.
10 Did this result agree with your prediction?
11 Does this result agree with what you have learned about particle theory?
[ planning, observing, presenting, considering, numeracy ]
7Gd/3 Fizzy drinks go flat
When you take the top off a can of fizzy drink and leave it, it goes 'flat' because the gas comes out of the water. In this experiment, you will be investigating what happens to the mass of the drink when the drink goes flat.
- Can of fizzy drink
- Balance
- Stop clock
Read the three predictions below. Do you agree with one of them? Which one?
Perhaps you've got another theory of your own?
1 Explain which prediction and explanation you think is correct. You may also be able to refer to other text books, or the work you have already done in this unit, to help you with your prediction.
2 Explain your prediction by drawing particle diagrams if you can.
3 Write a method for your investigation. You will need to record the results for about 5 minutes. How often do you think you will be able to take readings?
How accurate do you think the balance will need to be to get the results you need?
4 Design a table to show how the mass of the drink changes with time. Carry out your investigation.
Considering your results
5 Draw a graph to show how the mass varies with time. Join up the points with a line of best fit. (Is this a straight line or a curve?)
6 Was your prediction correct? If not, which theory do you now think is correct?
7 Use the graph to estimate the mass of the can of drink once it has gone completely flat.
[ planning, observing, presenting, considering ]
7Gd/4 Speeds of diffusion
In this experiment you will investigate what happens when two different gases diffuse through the air.
Hydrogen chloride and ammonia will react together to give a white solid.
When the two gases meet, this appears as white smoke in the air.
Particles of hydrogen chloride are about twice as heavy as particles of ammonia.
1 Copy the diagram.
2 How do you think the particles will move? Discuss your ideas with a partner.
3 Where in the tube do you think the two gases will meet? Put a cross on the diagram to show your prediction.
4 Explain your prediction in terms of the movement of particles.
5 When your teacher puts the cotton wool in the tube, start timing. Look carefully to see when the white smoke ring appears. As soon as you see the smoke, stop timing. Measure how far each gas has travelled.
6 Which gas moved faster? Did this agree with your prediction?
7 Do you think your original explanation was correct, or have you changed your ideas?
8 Use the formula to calculate the speed of each gas:
Speed =
Evaluation
9 Do you think that your results would support this conclusion?
10 Have you got enough results to be sure?
11 If this pattern worked, what result would you expect if you did an experiment where one gas was three times as heavy as the other?
[ observing, considering, evaluating, numeracy ]
7Gd/5 Diffusion
1 Jenna put a purple crystal into a beaker of water at 10 o'clock. She came back to look at the beaker at 12 o'clock, and again at 4 o'clock.
Colour in the beakers to show how far the purple colour would have spread at each time. The first one has been done for you.
10 o'clock 12 o'clock 4 o'clock
2 Fill in the gaps in these sentences, using words from the box. You may need to use some words more than once.
The colour in Jenna's beaker spread out by _______________________ . The water
_______________________ are moving around all the time. They bump into
_______________________ from the purple crystal, and _______________________ them
around. The purple gradually _______________________ out through the
_______________________ .
diffusion move particles spreads water
3 Mr Collins has got some new aftershave. Danny can smell it as soon as Mr Collins comes into the lab. Ramesh does not smell it until two minutes later.
a Who is sitting nearest to the lab door? ________________________________________
b Explain your answer _____________________________________________________
______________________________________________________________________
4 Diffusion happens faster in gases than in liquids. Why does this happen? Tick the correct explanation.
The particles in gases are smaller than the particles in liquids.
The particles in gases are bigger than the particles in liquids.
The particles in gases are moving faster than the particles in liquids.
The particles in gases are moving more slowly than the particles in liquids.
7Gd/6 Random motion
In this activity, you will look at a simple model of random motion.
- Worksheet 7Gd/7
- Dice
- Coloured pen or pencil
1 Start at the black dot in the middle of sheet 7Gd/7.
2 You will be moving one line at a time each time you throw the dice.
The direction of each move should be according to this key.
3 Predict how many throws you will take to get to the edge of the chart.
4 Now try it out. Throw the dice and draw a dot on the chart in the direction shown by the key.
5 Join up the dots to make a line.
6 Throw again and repeat the process.
7 Keep going until you get to the edge of the chart, or your diagram starts getting too complicated to see.
To think about …
On average, you have an equal chance of getting any of the six numbers on the dice. Would you expect the particle to stay in the middle of the sheet? Is that what happened in your activity?
7Gd/7 Grid sheet for random motion activity
7Ge/1 Gas pressure 1
bump decrease
force increase
less more
particles pressure
1 Fill in the gaps in these sentences using words from the box. You may use each word once, more than once or not at all.
The ___________________ in a gas are moving around all the time. The particles
___________________ into the sides of their container. The ___________________ of the
particles hitting the sides causes ___________________ . If you put more particles into a
container, there will be ___________________ particles to collide with the walls, and the
pressure will ___________________
2 Particles in the air bump into everything around us. There is air inside this empty bottle. Air particles are hitting the inside and the outside, and there is the same pressure inside and outside.
The air is being sucked out of the bottle.
a What will happen to the air pressure inside the bottle?
b What will happen to the bottle?
Explain your answer. ____________________________________________________
7Ge/2 Gas pressure 2
1 There is pressure on the inside and the outside of this plastic bottle.
a What is causing the force? Explain as fully as you can.
b What can you say about the size of the pressure inside and outside the bottle?
The air is being sucked out of this bottle.
c What will happen to the bottle as more and more air is taken out?
d Why will this happen? Explain as fully as you can.
If you try this at home, do it over a sink!
2 You can use a piece of card to make a lid for a glass full of water. The lid will keep the water in even if the glass is upside down!
a What makes the card stay up when the glass is upside down?
b This trick does not work if the glass is not completely full of water. Try to explain why. (Hint: think about what is in the part of the glass that is not full of water.)
3 Liquids are useful in car braking systems. When the brake pedal is pressed, some brake fluid is pushed along the brake pipe. The brake pads are pushed onto part of the wheel, making the car slow down. This would not work if the liquid could be squashed.
a Why is a liquid useful for making brakes work?
b Why could you not use a gas in the brake pipes. Explain as fully as you can, using ideas about particles.
7Ge/3 Revision puzzle
a
b
c
d
e
f
g
h
1 Write your answers to the clues in the grid above.
a Solids, liquids and gases all have different _______________________ .
b Everything is made of tiny pieces called _______________________ .
c Particles in a liquid or a gas can _______________________ around.
d A _______________________ has particles that are a long way apart.
e Smells spread through the air by _______________________ .
f If you pump all the air out of a space, you have a _______________________ .
g Particles in a solid cannot move around, they can only _______________________ .
h Solids and liquids both have fixed _______________________ .
2 Write down the word in the shaded boxes.
Now write your own clue for this word.
[ knowledge, literacy, revision ]
7Ge/4 Using expansion and contraction
This picture shows some telephone wires in summer.
1 When will the temperature be warmest: summer or winter?
2 When will the wires be longest: summer or winter? Explain your answer.
3 What would happen if the wires were put up so they were tight in the summer?
This picture shows an old house. The walls are not very strong, and the house has to be held together by a big metal bar through the middle. The bar was heated when it was put in, and the ends were fastened on before it cooled down.
4 Would the bar be longer when it is hot or cold?
5 What would happen to the bar as it cooled down?
6 Why do you think the bar was heated when it was put into the house?
This picture shows a bimetallic strip. It is a strip of two different metals joined together. It bends when it gets hot because one metal expands more than the other. It straightens out again when it gets cold.
7 Does the picture show the strip when it is hot or cold?
8 What will happen if the temperature goes down?
The strip is part of a switch. When the strip touches the contact, electricity can flow and switch the central heating on. This is called a thermostat.
9 How does the thermostat help to keep a house at a constant temperature?
10 Draw a switch (similar to the one above) that would switch on air conditioning if the temperature got too hot.
7G Summary Sheets
Solids, liquids and gases
SOLID
- Solids are made up of particles that are very close together and are held tightly together by strong bonds.
- Solids cannot be squashed, do not flow, have a fixed shape and volume, and have a high density.
LIQUID
- Liquids are made up of particles that are fairly close together; the bonds between the particles are weaker than the bonds in solids.
- Liquids cannot be squashed, flow quite easily, and have a fixed volume but no fixed shape.
- Although they are dense, liquids usually have a lower density than solids.
GAS
- Gases are made up of particles that are well spread out, with no bonds between them.
- Gases are quite easy to squash, flow easily, have no fixed volume and no fixed shape.
- Gases have a lower density than liquids.
Diffusion
The natural mixing of substances is called diffusion. Diffusion occurs because particles in a substance are always moving around. Diffusion is fastest in gases, and slower in liquids. Diffusion in solids is extremely slow.
Pressure in gases
Pressure is caused by particles hitting the walls of the container they are in. If the pressure becomes too great for a fixed container to hold, it will burst.
The pressure may increase because:
- the container has been squashed, making the volume smaller; this means that the particles will be hitting the walls more often.
- the number of particles has been increased, which means there are more particles moving around to hit the walls.
- the temperature of the particles has increased, so they will move around faster and hit the walls harder and more often.
If the particles are in a container which is flexible, like a balloon or a syringe, an increase in pressure will make the volume increase.
The idea of particles is a theory that scientists use to explain observations. Scientists use theories to make predictions, and test the predictions to find out if they are correct. If the predictions are not correct, then the theory may have to be changed to help to explain the new evidence.
7G Target Sheet
Topic
Targets
Before the unit
I have learned this
I have revised this
7Ga
Know that solids, liquids and gases have different properties.
Know the properties of solids.
Know the properties of liquids.
Know the properties of gases.
7Gb
Know how scientists develop theories.
Know what a theory is.
Know how scientists test theories.
Know some of the things that a theory about solids, liquids and gases would have to explain.
7Gc
Know that solids, liquids and gases are made up of particles.
Know how the particles are arranged in a solid.
Know how the particles are arranged in a liquid.
Know how the particles are arranged in a gas.
7Gd
Know how smells and colours can move from one place to another.
Know the word that describes this effect.
Know how quickly things spread out in gases and liquids.
Know how to explain this effect in terms of particle theory.
7Ge
Know what causes gas pressure.
Know how the pressure of a gas can be changed.
Be able to explain a change in gas pressure in terms of particles.
Be able to explain some effects of air pressure.
7G Word Sheets
Word sheets that include new words from the 'Focus on:' pages are available on the Exploring Science website.
7Ga - States matter
Word
Pronunciation
Meaning
Something which is heavy for its volume.
Move.
gas
Something that does not have a fixed shape or volume, and is easy to squash.
liquid
lick-wid
Something with a fixed volume but no fixed shape.
property
A description of how a material behaves and what it is like. Hardness is a property of some solids.
solid
Something with a fixed shape and volume.
states of matter
There are three different forms which a substance can be in; solid, liquid or gas. These are the three states of matter.
7Gb - In theory
data
Results of an experiment.
observation
What you see happening in an experiment.
prediction
What you think will happen in an experiment.
theory
thear-ree
An idea about why things work the way they do. Scientists use their imaginations to come up with a theory.
7Gc - Bits and pieces
bonds
Forces holding particles together.
particles
part-ick-als
The tiny pieces that everything is made out of.
vibrate
Move backwards and forwards.
7Gd - Aroma roamer
diffusion
When particles mix with each other without anything moving them.
7Ge - What a gas!/Summing up/Focus on: Changing size
pressure
presh-ur
The force caused by particles hitting a certain area.
vacuum
vack-yoom
A completely empty space.