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Primary Science · Year 4Chapter 6 · Solids, liquids and gases
Year 4 · Chapter 6

Solids, liquids and gases

By the end of this chapter you will be able to

  • Say what a solid, a liquid and a gas are like, and how each one behaves in a container
  • Sort everyday materials into solids, liquids and gases
  • Use a table to count how many materials are in each group
  • Explain that a liquid keeps its volume but changes its shape when it is poured
  • Plan and read a fair test that compares the shape of the same amount of water
  • Explain why the features of a material are used to group it

You should already know

  • Materials and their properties, such as hard, soft, rough and smooth (Year 1 and Year 2 Science)
  • Changing shape by squashing, bending and twisting solid objects (Year 2 Science, Chapter 10)

Where this leads

  • Changing state when heated or cooled, and the water cycle (Year 4 Science, Chapter 7)
  • The particle model of solids, liquids and gases (Year 6 Science)

National Curriculum for England, Key Stage 2 science, Year 4. Content: M1 compare and group materials together, according to whether they are solids, liquids or gases.

Exercise P  Do you remember?

1
FWhich kind of material can you pour: a solid or a liquid? Write the word.
2
FWhat unit is used to measure temperature? Write the words.
3
FName one material that is hard and keeps its shape. Write one material.
4
FWhat do we call water when it freezes? Write the word.
5
FIs air a solid? Write yes or no.
6.1

Solids

Year 4
M1: compare and group materials together, according to whether they are solids
Video lesson: SolidsComing soon
Story. Yusuf builds a tower of wooden blocks on the carpet. Priya puts a metal spoon on the blocks, and it stays where it is. “The blocks keep their shape, even when I touch them,” says Priya. Mr Patel says, “Those are solids.”

A solid keeps its own shape. It does not flow, and it is hard to squash. Wood, metal, rock, plastic and ice are all solids.

If you put a solid in a container, it stays the same shape. It does not spread out to fill the container.

Solidkeeps its own shapeLiquidtakes the shape of its containerGasspreads out to fill it
Three containers. The solid block of wood keeps its own shape.

Key ideas

  • A solid keeps its own shape.
  • A solid does not flow, and it is hard to squash.
  • Wood, metal, rock, plastic and ice are solids.
  • A solid stays the same shape in any container.
Worked example 6.1.1
Which of these is a solid: water, wood or milk? Write the word.

Method. Think about which one keeps its shape.

  1. Look at each one. Water and milk flow, so they are not solids. Wood keeps its own shape.
    keeps its shape
  2. Name the solid. So the solid is wood.
    wood
  3. Write the answer.
    wood

Check. Wood is hard and keeps its shape. ✓

Worked example 6.1.2
Is a metal spoon a solid? Write yes or no.

Method. Check the spoon.

  1. Check its shape. A metal spoon keeps its own shape and does not flow.
    keeps its shape
  2. Decide. So a metal spoon is a solid, and the answer is yes.
    yes
  3. Write the answer.
    yes

Check. Metal is hard and keeps its shape. ✓

Worked example 6.1.3
Is ice a solid, a liquid or a gas? Write the word.

Method. Think about ice.

  1. Think about its shape. A piece of ice keeps its own shape.
    own shape
  2. Name the state. So ice is a solid.
    solid
  3. Write the answer.
    solid

Check. Ice is frozen water, and it keeps its shape. ✓

Watch out

Watch out: a solid can be broken into small pieces, but each piece is still a solid. Solids do not become liquids just because they are cut up.

Try it at home or school (with a grown-up). Put a wooden block, a metal spoon and a plastic cup on a table, with a grown-up. Push each one gently with your finger. Say which one keeps its shape, and which one does not.

Exam tip

Grown-up tip. Ask: “Does it keep its shape when you put it down? Can you squash it?” Let your child use the words solid, hard and shape.

Exercise 6A  Solids

1
FWhich of these is a solid: water, wood or milk? Write the word.
2
FDo solids keep their own shape? Write yes or no.
3
FFill in the gap: a solid is hard to ___. Write the word.
4
FWhich of these is a solid: cooking oil or ice? Write the word.
5
FIs a metal spoon a solid? Write yes or no.
6
FName one solid from the list in section 6.4. Write one solid.
7
FA rock is hard and keeps its shape. Is it a solid or a liquid? Write the word.
8
FHow many of these are solids: wood, water and metal spoon? Write the number.
9
PSAli says a solid can always be poured. Is Ali right? Write yes or no.
10
PSDoes a solid change its shape when you put it on a table? Write yes or no.
11
PSWorking scientifically. Predict whether a block of wood will keep its shape if it is put in a bowl. Write yes or no.
12
RExplain why a metal spoon is a solid. Write one sentence.
6.2

Liquids

Year 4
M1: compare and group materials together, according to whether they are liquids
Video lesson: LiquidsComing soon
Story. At lunch, Aisha pours milk into a tall glass, and then into a small cup. “The milk has changed shape,” she says. Mr Patel says, “It takes the shape of the cup, because milk is a liquid.”

A liquid flows, and it can be poured. A liquid takes the shape of its container, so it is wider in a wide dish and taller in a tall glass. When a liquid is still, its top surface is flat.

Water, milk, cooking oil and orange juice are all liquids.

Key ideas

  • A liquid flows, and can be poured.
  • A liquid takes the shape of its container.
  • The top surface of a still liquid is flat.
  • Water, milk, cooking oil and orange juice are liquids.
Worked example 6.2.1
Is milk a solid or a liquid? Write the word.

Method. Think about whether milk flows.

  1. Think about pouring. Milk can be poured, so it flows.
    flows
  2. Name the state. A material that flows is a liquid.
    liquid
  3. Write the answer.
    liquid

Check. Milk takes the shape of the glass. ✓

Worked example 6.2.2
When water is still in a glass, what is the shape of its top surface? Write the word: flat or round.

Method. Look at the water in the glass.

  1. Look at the top. The top of still water is level, like a table.
    level
  2. Name the shape. The shape of the top surface is flat.
    flat
  3. Write the answer.
    flat

Check. A liquid has a flat top when it is still. ✓

Worked example 6.2.3
Is cooking oil a liquid? Write yes or no.

Method. Check whether cooking oil flows.

  1. Check the oil. Cooking oil pours out of a bottle, so it flows.
    pours
  2. Decide. So cooking oil is a liquid, and the answer is yes.
    yes
  3. Write the answer.
    yes

Check. Oil is a liquid, like water. ✓

Watch out

Watch out: a liquid does not keep its own shape. If you pour water into a jug, the water takes the shape of the jug, not the shape it had before.

Try it at home or school (with a grown-up). Pour a small cup of water into two different containers, such as a tall glass and a wide dish, with a grown-up. Look at the shape of the water in each one, and say what you notice.

Exam tip

Grown-up tip. Ask: “What shape is the water now? Is the top flat?” Let your child pour carefully over the sink or a tray.

Exercise 6B  Liquids

1
FWhich of these is a liquid: rock or milk? Write the word.
2
FDo liquids take the shape of their container? Write yes or no.
3
FWhat shape is the top surface of still water in a glass? Write the word: flat or round.
4
FFill in the gap: a liquid can be ___ from one container into another. Write the word.
5
FIs cooking oil a liquid? Write yes or no.
6
FIs orange juice a liquid? Write yes or no.
7
FWhich of these is a liquid: wood, water or ice? Write the word.
8
FHow many of these are liquids: water, milk, cooking oil and orange juice? Write the number.
9
PSMo pours 100 ml of water into a tall glass. He then pours the same water into a wide dish. How many ml of water is in the dish? Write the number.
10
PSRuby says a liquid keeps its shape when it is poured into a jug. Is Ruby right? Write yes or no.
11
PSWorking scientifically. Predict what shape the water will be in a wide, flat dish. Write one prediction.
12
RExplain why water changes shape when it is poured. Write one sentence.
6.3

Gases

Year 4
M1: compare and group materials together, according to whether they are gases
Video lesson: GasesComing soon
Story. Leo blows up a balloon. “What is inside it?” he asks. “Air,” says Mr Patel. “And the air spreads out to fill the whole balloon.” Later, Ruby opens a bottle of fizzy water, and bubbles rise. “Those are bubbles of a gas,” says Mr Patel.

A gas has no fixed shape. It spreads out to fill any container it is in. Gases are easy to squash, unlike solids.

Air is a gas. The bubbles in fizzy water are a gas called carbon dioxide.

Key ideas

  • A gas spreads out to fill its container.
  • A gas has no fixed shape.
  • A gas can be squashed, but a solid is hard to squash.
  • Air and the bubbles in fizzy water are gases.
Worked example 6.3.1
Does a gas fill the whole container it is in? Write yes or no.

Method. Think about a balloon.

  1. Think about the balloon. The air in a balloon spreads out to fill the whole balloon.
    fills the whole balloon
  2. Decide. So a gas fills the whole container, and the answer is yes.
    yes
  3. Write the answer.
    yes

Check. Gases spread out to fill the space. ✓

Worked example 6.3.2
What gas is in the bubbles in fizzy water? Write the name.

Method. Read the chapter.

  1. Read the chapter. The bubbles in fizzy water are a gas called carbon dioxide.
    carbon dioxide
  2. Name the gas. So the gas in the bubbles is carbon dioxide.
    carbon dioxide
  3. Write the answer.
    carbon dioxide

Check. Bubbles rise because they are a gas. ✓

Worked example 6.3.3
Which is a gas: ice or air? Write the word.

Method. Think about which one spreads out.

  1. Look at each one. Ice keeps its shape, but air spreads out to fill a container.
    spreads out
  2. Name the gas. So air is the gas.
    air
  3. Write the answer.
    air

Check. Ice is a solid, and air is a gas. ✓

Watch out

Watch out: you cannot see air, but it is still a material. Air is a gas, and it has weight. A gas is not “nothing”.

Try it at home or school (with a grown-up). Blow up a balloon with a grown-up, and feel the air inside it. Let it go and see which way the air rushes. Do not put a balloon in your mouth, and keep balloons away from small children.

Exam tip

Grown-up tip. Ask: “Can you see the air? Where does the air go in the balloon?” Let your child use the words gas and spreads out.

Exercise 6C  Gases

1
FWhich is a gas: air or ice? Write the word.
2
FDo gases fill the whole container they are in? Write yes or no.
3
FWhat gas is in the bubbles in fizzy water? Write the name.
4
FAre gases easy to squash? Write yes or no.
5
FDo gases have a fixed shape? Write yes or no.
6
FFill in the gap: gases spread out to ___ the container they are in. Write the word.
7
FAre the bubbles in fizzy water a gas? Write yes or no.
8
PSAli blows up a balloon. What fills the balloon? Write the word.
9
PSRuby says a gas has a flat top surface, like water in a glass. Is Ruby right? Write yes or no.
10
PSWorking scientifically. Predict what happens to the bubbles when a bottle of fizzy water is opened. Write one prediction.
11
RExplain why a gas can be squashed, but a solid is hard to squash. Write one sentence.
6.4

Comparing and grouping materials

Year 4
M1: compare and group materials together, according to whether they are solids, liquids or gases
Video lesson: Comparing and grouping materialsComing soon
Story. Mr Patel gives the class a box of materials. “Sort them into three groups,” he says. “Use what you have learned about how each one behaves.” Priya says, “I will use the groups solids, liquids and gases.”

To group materials, compare the features of each one. The first question is: does it keep its own shape? The second question is: does it flow? The third question is: does it spread out to fill the container? The table sorts 11 materials into the three groups.

MaterialSolid, liquid or gas?
woodsolid
icesolid
metal spoonsolid
rocksolid
plastic bottlesolid
waterliquid
milkliquid
cooking oilliquid
orange juiceliquid
airgas
bubbles in fizzy watergas

The same materials, grouped into three columns.

SolidsLiquidsGases
woodwaterair
icemilkbubbles in fizzy water
metal spooncooking oil
rockorange juice
plastic bottle

Key ideas

  • Group materials by comparing their features.
  • A solid keeps its shape. A liquid flows and takes the shape of its container. A gas spreads out to fill it.
  • Each material belongs to one group only.
  • Count the materials in each group to compare the groups.
Worked example 6.4.1
How many solids are in the table? Write the number.

Method. Count the solids in the table.

  1. Read the table. The solids are wood, ice, metal spoon, rock and plastic bottle.
    five names
  2. Count them. There are five solids in the table.
    5
  3. Write the answer.
    5

Check. The table has 11 materials in all. ✓

Worked example 6.4.2
How many gases are in the table? Write the number.

Method. Count the gases in the table.

  1. Read the table. The gases are air and the bubbles in fizzy water.
    two names
  2. Count them. There are two gases in the table.
    2
  3. Write the answer.
    2

Check. Two gases is the smallest group. ✓

Worked example 6.4.3
Which group has the most materials in the table? Write the word: solids, liquids or gases.

Method. Compare the three counts.

  1. Compare the counts. Solids 5, liquids 4 and gases 2.
    5, 4, 2
  2. Choose the biggest. The biggest count is 5, for solids.
    solids
  3. Write the answer.
    solids

Check. Five is more than four, and more than two. ✓

Watch out

Watch out: a bubble in fizzy water is a gas, even though the water around it is a liquid. Each material is grouped by the state of the material itself.

Try it at home or school (with a grown-up). Look at five things in your kitchen, with a grown-up. Sort them into solids, liquids and gases, and write one feature you used for each group. Do not taste any of them.

Exam tip

Grown-up tip. Ask: “Does it keep its shape? Does it pour? Does it spread out?” Let your child use the three questions to sort each thing.

Exercise 6D  Comparing and grouping materials

1
FLook at the table in section 6.4. Which material is a solid: plastic bottle or milk? Write the name.
2
FLook at the table in section 6.4. How many solids are there? Write the number.
3
FLook at the table in section 6.4. How many liquids are there? Write the number.
4
FLook at the table in section 6.4. How many gases are there? Write the number.
5
FLook at the table in section 6.4. How many materials are there altogether? Write the number.
6
FWhich group has the fewest materials in the table? Write the word: solids, liquids or gases.
7
FIs ice in the solid group? Write yes or no.
8
FWrite the group for orange juice: solid, liquid or gas.
9
PSAre wood and metal in the same group? Write yes or no.
10
PSWorking scientifically. Plan how you would sort the materials in your kitchen into solids, liquids and gases. Write one feature you would check first.
11
RExplain why materials are grouped by their features. Write one sentence.
6.5

A fair test on shape and amount

Year 4
M1: compare materials according to their state, using a fair test on the same amount of liquid
Video lesson: A fair test on shape and amountComing soon
Story. Sam pours 100 ml of water into a tall glass and then into a wide dish. “The dish holds more water, because it is wider,” he says. Ms Chen says, “Let us check. Keep the amount the same, and change only the container.”

A liquid keeps the same amount when it is poured into a different container. Only its shape changes. The amount is measured in millilitres (ml), and it stays the same.

The table shows the same 100 ml of water poured into two containers. The picture shows the two containers.

ContainerWater poured in (ml)Shape of the water
a tall, thin glass100takes the shape of the container
a wide, flat dish100takes the shape of the container
tall, thin glasswide, flat dish100 ml of water100 ml of water
The same 100 ml of water in a tall thin glass and in a wide flat dish. The water takes the shape of each container.

Key ideas

  • A liquid takes the shape of its container, but its amount stays the same.
  • Measure the amount in millilitres (ml).
  • In a fair test, change only the container, and keep the amount the same.
  • A wide container does not hold more liquid than a tall one, if the amount is the same.
Worked example 6.5.1
How much water was poured into the wide, flat dish? Write the number of millilitres.

Method. Read the table.

  1. Read the row. The wide, flat dish row says 100 ml of water was poured in.
    100 ml
  2. Write the number. So the dish had 100 ml of water.
    100
  3. Write the answer.
    100

Check. The same amount was poured into each container. ✓

Worked example 6.5.2
Sam says the dish holds more water, because it is wider. Is Sam right? Write yes or no.

Method. Compare the amounts in the table.

  1. Compare them. Both containers had 100 ml of water poured in.
    both 100 ml
  2. Decide. The amount is the same, so Sam is not right.
    no
  3. Write the answer.
    no

Check. Only the shape of the water changed. ✓

Worked example 6.5.3
In this fair test, what is the one thing that is changed? Write the word: shape or amount.

Method. Think about the test.

  1. Think about the containers. The container changes, so the shape of the water changes.
    shape
  2. Check the amount. The amount of water is kept the same, so the amount is not changed.
    kept the same
  3. Write the answer.
    shape

Check. In a fair test, only one thing is changed. ✓

Watch out

Watch out: a wide container does not hold more liquid than a tall one, if both have the same amount inside. Wide means the water is spread out, not that there is more of it.

Try it at home or school (with a grown-up). Pour one cup of water into a tall glass, and then into a wide bowl, with a grown-up. Look at the water in each one. Keep the amount the same. Say what changed, and what stayed the same.

Exam tip

Grown-up tip. Ask: “Did the amount change? What changed?” Let your child measure with a measuring jug, and pour carefully over a tray.

Exercise 6E  A fair test on shape and amount

1
FLook at the table in section 6.5. How much water was poured into the tall, thin glass? Write the number of millilitres.
2
FLook at the table in section 6.5. How much water was poured into the wide, flat dish? Write the number of millilitres.
3
FDid the amount of water change between the glass and the dish? Write yes or no.
4
FIn the fair test, which feature of the water changed? Write the word: shape or amount.
5
FFill in the gap: a liquid keeps the same amount, but changes its ___. Write the word.
6
FWhat unit is the amount of water measured in? Write the unit: ml or cm.
7
PSSam says the dish holds more water, because it is wider. Is Sam right? Write yes or no.
8
PSWorking scientifically. Plan a safe test to find out whether a material is a solid. Write one test you would do.
9
PSWhich material fills a balloon completely: air or wood? Write the word.
10
RExplain why the same water looks different in the glass and the dish, but has the same amount. Write one sentence.

Chapter summary

SkillMethod
SolidKeeps its own shape. Hard to squash. Does not flow. Examples: wood, metal, rock, plastic, ice.
LiquidFlows and can be poured. Takes the shape of its container, but keeps the same amount. Examples: water, milk, oil, juice.
GasSpreads out to fill its container. Can be squashed. Examples: air, the bubbles in fizzy water.
GroupingCompare the features of each material. Each material belongs to one group.
Fair testKeep the amount the same, and change only the container. Measure the amount in ml.

Can you…?

  • I can say what a solid, a liquid and a gas are like
  • I can sort everyday materials into solids, liquids and gases
  • I can count the materials in each group, using a table
  • I can explain that a liquid keeps the same amount but changes its shape
  • I can plan and read a fair test on the shape of a liquid
  • I can explain why materials are grouped by their features

Key terms

solid
a material that keeps its own shape and does not flow
liquid
a material that flows, can be poured, and takes the shape of its container
gas
a material that has no fixed shape and spreads out to fill its container
material
what something is made of, such as wood, water or air
state
whether a material is a solid, a liquid or a gas
carbon dioxide
the gas in the bubbles in fizzy water
volume
how much space something takes up, or how much liquid there is
millilitre
a unit for measuring an amount of liquid, written ml

Exercise 6Z  Check-up

1
Which is a solid: milk, wood or air? Write the word.
2
Do liquids keep their own shape? Write yes or no.
3
What gas is in the bubbles in fizzy water? Write the name.
4
Look at the table in section 6.4. How many materials are there altogether? Write the number.
5
Name one material that is a liquid, from the table in section 6.4. Write one material.
6
Is a rock a solid? Write yes or no.
7
A tall glass and a wide dish each have 100 ml of water in them. Which has more water? Write the word: glass, dish or same.
8
Which state is it when a material spreads out to fill its container: solid, liquid or gas? Write the word.
9
Ruby says a solid can be poured like a liquid. Is Ruby right? Write no, and give one reason.
10
Explain how a gas differs from a solid, in one sentence.

Total 16 marks. Allow about 16 minutes.

Exercise 6X  Practice test questions

1
FWhich of these is a solid: milk, wood or air? Write the word.[1 mark]
2
FDo liquids keep their own shape? Write yes or no.[1 mark]
3
FWhat gas is in the bubbles in fizzy water? Write the name.[1 mark]
4
FWrite the state of this material: it spreads out to fill any container it is in. Write the word: solid, liquid or gas.[1 mark]
5
FWrite the state of each material, in this order: wood, water, air. Write the three words, separated by semicolons.[2 marks]
6
FWrite the names of two solids.[2 marks]
7
RExplain why a gas can be squashed, but a solid is hard to squash. Write one sentence.[2 marks]
8
FSort these into the three groups: air, ice and cooking oil. Write the answer as: gas: ...; solid: ...; liquid: ...[3 marks]
9
PSA tall glass and a wide dish each have 100 ml of water. Write the number of millilitres in the wide dish.[1 mark]
10
RExplain why the water in a wide dish is not more water than the water in a tall glass, if both have 100 ml. Write one sentence.[2 marks]
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