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Primary Science · Year 3Chapter 7 · Rocks, fossils and soils
Year 3 · Chapter 7

Rocks, fossils and soils

By the end of this chapter you will be able to

  • Describe rocks by their colour, texture, layers, sparkly crystals and holes, and sort them into groups
  • Say whether a rock is hard or soft, and whether water can soak into it (permeable)
  • Name the four parts of soil: broken-down rock, organic matter, air and water
  • Read the results of a fair test on how water soaks through soils, and say what was changed and measured
  • Say what a fossil is, and tell remains from traces
  • Put the stages of fossil formation in order, and read the layers of rock in a diagram

You should already know

  • The parts of a flowering plant, including the roots (Year 3 Science, Chapter 2)
  • What plants need from the soil: water and nutrients (Year 3 Science, Chapter 3)

Where this leads

  • Light and shadows, and more fair tests (Year 3 Science, Chapter 8)
  • The properties of materials in more detail (Year 5 Science)

National Curriculum for England, Key Stage 2 science, Year 3. Content: R1 compare and group together different kinds of rocks on the basis of their appearance and simple physical properties, R2 describe in simple terms how fossils are formed when things that have lived are trapped within rock, R3 recognise that soils are made from rocks and organic matter.

Exercise P  Do you remember?

1
FWhich part of a plant takes in water from the soil? Write the part.
2
FWhat do plants take from the soil, apart from water? Write one word.
3
FWhat is the frame of bones inside the body called? Write the word.
4
FWhich cord joins a muscle to a bone? Write the word.
5
FWhich animal has a skeleton inside its body: a dog or a snail? Write the animal.
7.1

Different kinds of rock

Year 3
R1: compare and group together different kinds of rocks on the basis of their appearance
Video lesson: Different kinds of rockComing soon
Story. Zainab and Kofi have six rock samples, labelled A to F. Kofi says, “They all look the same to me.” Zainab looks closer. “No, some have stripes, and some have sparkles. Let’s sort them.”

A rock is a hard, natural material that is found in the ground. Rocks come in many different kinds. Scientists compare rocks by how they look:

Two rocks can be the same colour and still be very different. Look at the six samples in the picture.

ABCDEF
Six rock samples, A to F.

Key ideas

  • A rock is a hard, natural material found in the ground.
  • Rocks can be compared and grouped by their colour, texture, layers, sparkly crystals and holes.
  • Texture means how a rock looks and feels: smooth, rough, crumbly or gritty.
  • Two rocks can look alike in one way, and be different in another way.
Worked example 7.1.1
Look at the picture. Which sample has flat layers and is dark grey? Write the letter.
ABCDEF

Method. Find the samples that have layers, then find the dark grey one.

  1. Find the layers. Samples A and D have flat layers.
    A, D
  2. Find the colour. Sample A is dark grey. Sample D is light brown.
    A is dark grey
  3. Choose the one that matches both. Sample A has layers and is dark grey.
    A
  4. Write the answer.
    A

Check. Sample D has layers, but it is light brown, not dark grey. ✓

Watch out. Use both clues. Colour alone is not enough.

Worked example 7.1.2
Look at the picture. Which sample has sparkly crystals? Write the letter.
ABCDEF

Method. Look for the small white sparkles in the samples.

  1. Look at each sample. Sample C has small white sparkles and black dots.
    sparkles on C
  2. Check the others. None of the other samples has sparkles.
    only C
  3. Write the answer. So the sample with sparkly crystals is C.
    C
  4. Write the answer.
    C

Check. Sample E has holes, not sparkles. ✓

Worked example 7.1.3
Look at the picture. Which two samples look smooth? Write the two letters, in any order.
ABCDEF

Method. Find the samples whose texture is smooth.

  1. Read the textures. Samples A and F are smooth. The others are rough, gritty or crumbly.
    A and F
  2. Write the answer. So the two smooth samples are A and F.
    A, F
  3. Write the answer.
    A, F

Check. Sample F is smooth and shiny, with thin lines. ✓

Watch out. Smooth is about the texture. Layers and colour are different clues.

Watch out

Watch out: grey does not mean the same kind of rock. Look at the texture, the layers and the holes too, as well as the colour.

Try it at home or school (with a grown-up). Look at stones you already have at home, or in a garden you are allowed to use. Do not collect stones from walls, cliffs or protected places. Sort them into two groups: stones with stripes or layers, and stones without. Wash your hands afterwards.

Exam tip

Grown-up tip. Ask: “How does this stone feel? Is it smooth, rough or gritty? Does it have stripes?” Let your child use the words texture and layers.

Exercise 7A  Different kinds of rock

1
FLook at the picture. Which sample is white and crumbly? Write the letter.
ABCDEF
2
FLook at the picture. Which sample has holes? Write the letter.
ABCDEF
3
FLook at the picture. Which sample has sparkly crystals? Write the letter.
ABCDEF
4
FLook at the picture. Which samples have layers? Write the letters, in any order.
ABCDEF
5
FLook at the picture. Which sample is light brown with tiny grains? Write the letter.
ABCDEF
6
FLook at the picture. Write the letters of the two samples that look smooth, in any order.
ABCDEF
7
FFill in the gaps, using the picture of the six samples.
ABCDEF
(a)Sample ___ is red-brown and has holes.
(b)Sample ___ is smooth and shiny, with thin lines.
8
PSKofi says two grey rocks must be the same kind of rock, because they are both grey. Is Kofi right? Write no or yes.
9
PSWrite one way to tell two grey rocks apart, using only what you can see or feel. Write one answer.
10
PSSort the six samples into two groups: samples with layers, and samples without layers. Write the letters for each group.
ABCDEF
(a)Samples with layers
(b)Samples without layers
11
RKofi says a rock with holes must be soft. Is Kofi right? Write no or yes, and give one reason.
7.2

Hard, soft and permeable rocks

Year 3
R1: compare and group together rocks on simple physical properties, such as hardness and whether water soaks in
Video lesson: Hard, soft and permeable rocksComing soon
Story. Mo drips a drop of water onto two stones. On one stone the drop sits on top. On the other stone the drop soaks in and disappears. Mr Patel says, “The stone that lets water in is permeable.”

A material is permeable if water can soak into it or pass through it. A material is impermeable if water cannot soak into it or pass through it.

A rock is hard if it does not crumble when you press it gently. A rock is soft if it crumbles.

To make a fair test, scientists use the same amount of water for each sample, and the same time limit. In the class test, each sample had 5 ml of water dropped on it, and the time was 60 seconds. The table shows the results.

The water stays on top.Not permeable.The water soaks in.Permeable.
Left: the water stays on top, so the rock is not permeable. Right: the water soaks in, so the rock is permeable.
SampleColourHow it looks and feelsLayers?Hard or soft?Water soaks in?
Adark greysmoothyeshardno, not within 60 seconds
Bwhitecrumblynosoftyes, in 5 seconds
Cgrey, with black and white dotsroughnohardno, not within 60 seconds
Dlight browngritty, with tiny grainsyeshardyes, in 20 seconds
Ered-brownrough, with small holesnohardyes, in 10 seconds
Fwhitesmooth and shiny, with thin linesnohardno, not within 60 seconds

Key ideas

  • A material is permeable if water can soak into it or pass through it.
  • A material is impermeable if water cannot soak into it or pass through it.
  • A hard rock does not crumble when pressed gently. A soft rock crumbles.
  • A fair test uses the same amount of water and the same time limit for every sample.
Worked example 7.2.1
Look at the table in this section. Which sample is soft? Write the letter.

Method. Find the soft sample in the table.

  1. Read the column Hard or soft? Only one sample is soft.
    soft
  2. Name the sample. Sample B is soft.
    B
  3. Write the answer.
    B

Check. Sample B is also crumbly. ✓

Worked example 7.2.2
Look at the table in this section. Which sample let water soak in the fastest? Write the letter.

Method. Look for the smallest number of seconds in the column Water soaks in.

  1. Read the column. Sample B soaked in after 5 seconds. D took 20 seconds, and E took 10 seconds.
    5 seconds
  2. Choose the smallest. The smallest time is 5 seconds, from sample B.
    B
  3. Write the answer.
    B

Check. Sample B is the fastest, at 5 seconds. ✓

Worked example 7.2.3
Look at the table in this section. Does sample A let water soak in? Write yes or no.

Method. Read the row for sample A.

  1. Read the column Water soaks in? The table says no, not within 60 seconds.
    no
  2. Write the answer. So sample A is not permeable.
    no
  3. Write the answer.
    no

Check. Sample A is one of the samples that water did not soak into. ✓

Watch out

Watch out: hard does not mean impermeable. Samples D and E are both hard, and water soaks into both of them.

Try it at home or school (with a grown-up). Find a flat stone, or use a stone from home. Drip one small drop of water on it, and count the seconds until it soaks in or stays on top. Wipe the stone dry afterwards. Do not use hot water, and wash your hands at the end.

Exam tip

Grown-up tip. Ask: “Did the water stay on top, or did it soak in? How many seconds did it take?” Let your child say the word permeable, and explain what it means.

Exercise 7B  Hard, soft and permeable rocks

1
FLook at the table in this section. Which sample is soft? Write the letter.
2
FLook at the table in this section. Which samples let water soak in? Write the letters, in any order.
3
FLook at the table in this section. Which sample let water soak in after 10 seconds? Write the letter.
4
FLook at the table in this section. Which samples did not let water soak in within 60 seconds? Write the letters, in any order.
5
FA material that water can soak into is called ___. Write the word.
6
FA material that water cannot soak into is called ___. Write the word.
7
FIs sample F permeable? Write yes or no.
8
FIs sample D hard? Write yes or no.
9
PSMo says hard rocks cannot be permeable. Is Mo right? Write no or yes, and give one example from the table.
10
PSA new sample is soft and crumbly. Predict whether water will soak into it. Write yes or no, and give one reason.
11
PSWorking scientifically. Plan a fair test to compare two samples. Write one thing that must stay the same for both samples.
12
RExplain how you could test whether a stone is soft, safely. Write one sentence.
7.3

What soil is made of

Year 3
R3: recognise that soils are made from rocks and organic matter
Video lesson: What soil is made ofComing soon
Story. Fatima digs in the garden and finds dark, damp soil. A worm wriggles away from her spade. “What is soil made of?” she asks. Mr Patel says, “Let’s find out.”

Soil is the layer on the top of the ground, where plants grow. Soil is made from broken-down rock and organic matter. It also has air and water in the gaps between the pieces.

Part of soilWhat it is
broken-down rockpieces of rock, from big grains of sand to tiny clay pieces
organic matterdead plants and animals, and their waste, which break down slowly
airthe gaps between the pieces
waterwater that fills some of the gaps

Organic matter is the dead plants and animals in soil, and their waste. It breaks down slowly. Many living things also live in soil, such as earthworms, woodlouse and beetles.

grey dots: broken-down rockbrown shapes: organic matterwhite circles: airblue circles: water
Soil drawn as shapes. The legend shows what each shape means.

Key ideas

  • Soil is made from broken-down rock and organic matter.
  • Organic matter is dead plants and animals, and their waste, which break down.
  • Air and water fill the gaps between the pieces of soil.
  • Living things, such as earthworms, live in soil.
Worked example 7.3.1
Which part of soil comes from rock being broken into small pieces? Write the words.

Method. Read the table of the parts of soil.

  1. Read the table. Broken-down rock is made of pieces of rock, from big grains of sand to tiny clay pieces.
    broken-down rock
  2. Write the answer. So the part is broken-down rock.
    broken-down rock
  3. Write the answer.
    broken-down rock

Check. Soil is made from rocks and organic matter. ✓

Worked example 7.3.2
What is the name for dead plants and animals in soil, which break down? Write the words.

Method. Read the table of the parts of soil.

  1. Read the table. The dead plants and animals, and their waste, are called organic matter.
    organic matter
  2. Write the answer. So the name is organic matter.
    organic matter
  3. Write the answer.
    organic matter

Check. Organic matter breaks down slowly. ✓

Worked example 7.3.3
Name one living thing that lives in soil. Write the name.

Method. Think about the animals that live in the ground.

  1. Think about soil. Many living things live in soil.
    living things
  2. Name one. An earthworm is a living thing that lives in soil.
    earthworm
  3. Write the answer.
    Accept any one of: earthworm, woodlouse, beetle.

Check. Living things help to break down organic matter. ✓

Watch out. A living thing is not the same as organic matter. The living thing is alive; organic matter is dead.

Watch out

Watch out: soil is not only sand or mud. It also has organic matter, air and water in it.

Try it at home or school (with a grown-up). With a grown-up, scoop a spoonful of soil from a garden or a plant pot. Wash your hands afterwards. Use a magnifying glass to look for pieces of rock, bits of leaf and tiny gaps. Do not touch wild animals, and never put soil in your mouth.

Exam tip

Grown-up tip. Ask: “What can you see in the soil? Is any of it from a plant or an animal?” Let your child use the words broken-down rock and organic matter.

Exercise 7C  What soil is made of

1
FWhat is the name for dead plants and animals in soil that break down? Write the name.
2
FWhich part of soil comes from rock being broken into pieces? Write the name.
3
FName one living thing that lives in soil. Write the name.
4
FWhich two things fill the gaps in soil? Write both.
5
FTrue or false: soil is made only from sand. Write true or false.
6
FTrue or false: soil can have living things in it. Write true or false.
7
FFill in the gaps.
(a)Soil is made from broken-down ___.
(b)Soil also contains organic ___.
8
FLook at the picture of soil. Which shape means air? Write the shape.
grey dots: broken-down rockbrown shapes: organic matterwhite circles: airblue circles: water
9
PSSam says soil has nothing alive in it. Is Sam right? Write no or yes, and give one reason.
10
PSLook at the picture of soil. Which shape means water? Write the shape.
grey dots: broken-down rockbrown shapes: organic matterwhite circles: airblue circles: water
11
PSWorking scientifically. Predict what will happen to a dead leaf left on soil for a long time. Write one prediction.
12
RExplain why plants need soil. Write one sentence.
7.4

Water through soils: a fair test

Year 3
R3: soils are made from rocks and organic matter; the soil types differ in how water soaks through them
Video lesson: Water through soils: a fair testComing soon
Story. Kofi and Zainab test three soils. Kofi says, “I think the sandy soil will let the water through fastest.” Zainab says, “Let’s measure it, so we can check.”

The children put the same amount of each soil in a funnel. They pour 100 ml of water into each funnel. After 1 minute, they measure how much water has come through into the cup. They do three trials for each soil, and find the mean (the average) of the three trials.

The one thing they changed was the type of soil. The thing they measured was the water collected. Everything else was kept the same, so the test is fair.

Sandy soil has big pieces, with big gaps between them, so water runs through quickly. Clay soil has tiny pieces that fit closely, so the gaps are small and the water moves slowly. Garden soil is a mixture, so it lets water through at a speed in between.

050100mlsandy soilgarden soilclay soil
Three funnels of soil over cups. The cups show the mean of three trials for each soil.
SoilTrial 1 (ml)Trial 2 (ml)Trial 3 (ml)Mean (ml)
sandy soil88929090
garden soil42384040
clay soil1281010
050100ml collected (mean)90sandy soil40garden soil10clay soil
A bar chart of the mean water collected in 1 minute, for each soil.

Key ideas

  • A fair test changes only one thing. Here the thing changed is the type of soil.
  • The thing that is measured is the water collected in the cup after 1 minute.
  • Do three trials and find the mean, so that one odd result does not mislead you.
  • Sandy soil let the most water through. Clay soil let the least.
Worked example 7.4.1
Look at the table in this section. Which soil let the most water through? Write the soil.

Method. Find the highest mean in the Mean (ml) column.

  1. Read the means. The means are 90 ml for sandy soil, 40 ml for garden soil and 10 ml for clay soil.
    90 ml
  2. Choose the highest. The highest mean is 90 ml, for sandy soil.
    sandy soil
  3. Write the answer.
    sandy soil

Check. Sandy soil lets water through fastest. ✓

Worked example 7.4.2
Look at the table in this section. What is the mean of the three trials for garden soil? Write the number.

Method. Add the three trials for garden soil, then divide by 3.

  1. Add the trials. The trials are 42 ml, 38 ml and 40 ml. 42 + 38 + 40 = 120.
    120
  2. Divide by 3. The mean is 120 divided by 3, which is 40.
    40
  3. Write the answer.
    40

Check. The mean is 40 ml, which matches the table. ✓

Worked example 7.4.3
Using the means in the table, how many ml more came through the sandy soil than the clay soil? Write the number.

Method. Subtract the mean for clay soil from the mean for sandy soil.

  1. Read the means. The mean for sandy soil is 90 ml. The mean for clay soil is 10 ml.
    90 and 10
  2. Subtract. The difference is 90 minus 10, which is 80.
    80
  3. Write the answer.
    80

Check. Check: 10 + 80 = 90. ✓

Watch out. Use the means, not the single trials, so the answer is fair.

Watch out

Watch out: the water left in the soil was not measured. Only the water that came through into the cup counts.

Try it at home or school (with a grown-up). With a grown-up, cut the top off a clean plastic bottle to make a funnel. Put a little cotton wool in the neck. Put the same amount of sand in one funnel and the same amount of garden soil in another. Pour the same amount of water into each, and count for one minute. Which soil lets the water through fastest? Wash your hands afterwards.

Exam tip

Grown-up tip. Ask: “What did you change? What did you keep the same? Which funnel was fastest?” Let your child use the words fair test and mean.

Exercise 7D  Water through soils: a fair test

1
FLook at the picture of the funnels. Which soil let the most water through? Write the soil.
050100mlsandy soilgarden soilclay soil
2
FLook at the picture of the funnels. Which soil let the least water through? Write the soil.
050100mlsandy soilgarden soilclay soil
3
FLook at the table in this section. What is the mean for clay soil? Write the number.
4
FHow much water was poured into each funnel, in ml? Write the number.
5
FWhat was changed in the test? Write the words.
6
FWhat was measured in the test? Write the words.
7
FLook at the bar chart in this section. Which bar is the shortest? Write the soil.
050100ml collected (mean)90sandy soil40garden soil10clay soil
8
PSUsing the means, how many ml more came through garden soil than clay soil? Write the number.
9
PSPut the three soils in order, from the most water through to the least. Write the three soils.
10
PSWhy were three trials done for each soil? Write one reason.
11
PSRuby says the test shows that sandy soil has more nutrients. Is Ruby right? Write no or yes, and give one reason.
12
RExplain why clay soil lets less water through than sandy soil. Write one sentence.
13
PSWorking scientifically. Plan one change that would make this test fairer. Write one sentence.
7.5

What a fossil is

Year 3
R2: describe in simple terms how fossils are formed when things that have lived are trapped within rock
Video lesson: What a fossil isComing soon
Story. Priya finds a grey stone on the beach. It has a pattern that looks like a shell. Mr Patel says, “That could be a fossil, or it could just be a stone.” Priya asks, “How can we tell?”

A fossil is the remains, or a trace, of something that lived a very long time ago. Fossils are kept in rock.

Most fossils are found in rock. A stone that only looks like a shell is not a fossil, because a fossil must have come from something that once lived.

a shell kept in rocka footprint kept in rock
Left: a shell kept in rock, which is a fossil remains. Right: a footprint kept in rock, which is a fossil trace.

Key ideas

  • A fossil is the remains, or a trace, of something that lived a very long time ago.
  • A body fossil is a part of the living thing, such as a bone, a tooth, a shell or a leaf.
  • A trace fossil is a sign that a living thing was there, such as a footprint.
  • Fossils are kept in rock. A stone that only looks like a shell is not a fossil.
Worked example 7.5.1
Look at the picture. Is a shell kept in rock a fossil? Write yes or no.
a shell kept in rocka footprint kept in rock

Method. Think about what a fossil is.

  1. Read the definition. A fossil is the remains, or a trace, of something that lived long ago, kept in rock.
    remains in rock
  2. Check the shell. The shell lived long ago, and it is kept in rock.
    yes
  3. Write the answer.
    yes

Check. The shell is a fossil remains. ✓

Worked example 7.5.2
Look at the picture. Is the footprint kept in rock a body fossil or a trace fossil? Write the words.
a shell kept in rocka footprint kept in rock

Method. Think about what a footprint is.

  1. Read the definitions. A body fossil is part of the living thing. A trace fossil is a sign that it was there.
    trace fossil
  2. Choose the words. A footprint is a sign that an animal was there, so it is a trace fossil.
    trace fossil
  3. Write the answer.
    trace fossil

Check. A footprint is a trace fossil, not a part of the animal. ✓

Worked example 7.5.3
Which is a fossil: a bone kept in rock, or a stone that looks like a bone? Write the answer.

Method. Think about where the bone came from.

  1. Think about each one. A bone kept in rock came from a living thing. A stone that looks like a bone did not.
    living thing
  2. Write the answer. So a fossil is a bone kept in rock.
    a bone kept in rock
  3. Write the answer.
    a bone kept in rock

Check. A fossil must have come from something that once lived. ✓

Watch out

Watch out: a stone shaped like a shell is not a fossil. A fossil must come from something that once lived.

Try it at home or school (with a grown-up). With a grown-up, press a shell or a leaf into a lump of modelling clay. Lift it away carefully, and look at the print it leaves. The print is a bit like a trace. Wash your hands afterwards. Do not dig into cliffs, and do not break rocks to look for fossils.

Exam tip

Grown-up tip. Ask: “Is the print a part of the shell, or a sign that the shell was there?” Let your child choose the words body fossil or trace fossil.

Exercise 7E  What a fossil is

1
FWhat is a fossil? Write one short phrase.
2
FIs a tooth kept in rock a body fossil or a trace fossil? Write the words.
3
FIs a footprint kept in rock a body fossil or a trace fossil? Write the words.
4
FFill in the gap: most fossils are found in ___. Write the word.
5
FTrue or false: a fossil is made from something that has lived. Write true or false.
6
FTrue or false: a stone shaped like a shell is always a fossil. Write true or false.
7
FLook at the picture. Is the shell kept in the rock on the left a fossil? Write yes or no.
a shell kept in rocka footprint kept in rock
8
FLook at the picture. Is the footprint on the right a body fossil or a trace fossil? Write the words.
a shell kept in rocka footprint kept in rock
9
PSLily finds a print of a leaf in a rock. Is it a fossil? Write yes or no, and give one reason.
10
PSMo says a fossil is a living animal kept in a museum. Is Mo right? Write no or yes.
11
PSWorking scientifically. Write one safe way to learn about fossils.
12
RExplain why a fossil has to be kept in rock. Write one sentence.
7.6

How fossils form in layers

Year 3
R2: fossils form when remains are trapped in layers of rock; the layers build up over a very long time
Video lesson: How fossils form in layersComing soon
Story. Kofi looks at a picture of a shell lying on the bottom of the sea. “Will that shell ever turn into rock?” he asks. Mr Patel says, “Let’s put the stages in order.”

Most fossils form in layers. Here are the four stages of how a fossil forms. The pictures are not in order.

StageWhat happens
AA living thing dies and sinks to the bottom of a lake or the sea.
BSand and mud cover it, and it is buried.
CMore layers build up over a very long time. The lower layers are squashed and stuck together into rock.
DWind and rain wear the rock away, and the fossil is found.

Sand and mud that settle in layers are called sediment. New layers build up on top of older layers. A layer is one flat band of rock. In layers that have not been turned over, the bottom layer is the oldest, and the top layer is the newest.

BDAC
Four pictures of fossil formation, labelled A to D. They are not in order.
1Layer 1: top, newest2Layer 23Layer 34Layer 45Layer 5: bottom, oldestnewerolder
A cross-section of five layers of rock. Layer 1 is the newest, and layer 5 is the oldest.

Key ideas

  • Fossils form when remains are buried in sediment, such as sand or mud.
  • Layers build up over a very long time, and the lower layers are squashed into rock.
  • In layers that have not been turned over, the lowest layer is the oldest.
  • A fossil can be found when the rock above it is worn away.
Worked example 7.6.1
Look at the diagram of layers. Which layer is the oldest? Write the number.
1Layer 1: top, newest2Layer 23Layer 34Layer 45Layer 5: bottom, oldestnewerolder

Method. Find the lowest layer.

  1. Look at the layers. Layer 1 is at the top, and layer 5 is at the bottom.
    bottom
  2. Choose the oldest. The bottom layer is the oldest, so it is layer 5.
    5
  3. Write the answer.
    5

Check. Layer 1 is the newest. ✓

Watch out. Oldest means it formed first. The bottom layer was laid down first.

Worked example 7.6.2
Look at the diagram of layers. Which layer is the newest? Write the number.
1Layer 1: top, newest2Layer 23Layer 34Layer 45Layer 5: bottom, oldestnewerolder

Method. Find the top layer.

  1. Look at the layers. The top layer is the newest layer.
    top
  2. Write the number. The top layer is layer 1.
    1
  3. Write the answer.
    1

Check. Layer 5 is the oldest. ✓

Worked example 7.6.3
Look at the four stages in the table. Which stage comes first? Write the letter.

Method. Read the stages in the table.

  1. Read stage A. A living thing dies and sinks to the bottom, so this is the first stage.
    A
  2. Write the answer. So the first stage is A.
    A
  3. Write the answer.
    A

Check. Stage B is the next stage: sand and mud cover the remains. ✓

Watch out

Watch out: the top layer is the newest, not the oldest. The oldest layers are at the bottom, if the layers have not been turned over.

Try it at home or school (with a grown-up). With a grown-up, put layers of different coloured sand, or dry rice, in a clear cup. Add one layer at a time, and press it gently before you add the next. Put a small plastic shell in one layer, and cover it with more layers. Talk about which layer would be the oldest. Wash your hands afterwards.

Exam tip

Grown-up tip. Ask: “Which layer did we add first? Which layer is the oldest?” Let your child explain how the layers build up, step by step.

Exercise 7F  How fossils form in layers

1
FLook at the diagram of layers. Which layer is the oldest? Write the number.
1Layer 1: top, newest2Layer 23Layer 34Layer 45Layer 5: bottom, oldestnewerolder
2
FLook at the diagram of layers. Which layer is the newest? Write the number.
1Layer 1: top, newest2Layer 23Layer 34Layer 45Layer 5: bottom, oldestnewerolder
3
FLook at the diagram of layers. Which layer has the fossil in it? Write the number.
1Layer 1: top, newest2Layer 23Layer 34Layer 45Layer 5: bottom, oldestnewerolder
4
FLook at the diagram of layers. Is layer 4 older or newer than layer 2? Write older or newer.
1Layer 1: top, newest2Layer 23Layer 34Layer 45Layer 5: bottom, oldestnewerolder
5
FFill in the gap. Write the word for the sand and mud that settle in layers and bury remains.
6
PSWrite the letters of the four stages in order, from first to last. Use the four pictures.
BDAC
7
FWhich stage has the rock being worn away, so that the fossil is found? Write the letter.
BDAC
8
FWhich stage has a living thing sinking to the bottom? Write the letter.
BDAC
9
PSRuby says the top layer must be the oldest. Is Ruby right? Write no or yes.
10
PSWorking scientifically. Predict what will happen to the lower layers if sand and mud keep settling on top for a very long time. Write one prediction.
11
PSWorking scientifically. Plan how to make a model of layers in a clear cup. Write one step.
12
RExplain why a fossil is more likely to form if an animal is buried quickly in sand or mud. Write one sentence.

Chapter summary

SkillMethod
Kinds of rockCompare rocks by colour, texture, layers, sparkly crystals and holes.
Hard and softA hard rock does not crumble when pressed gently; a soft rock crumbles.
PermeableA material is permeable if water can soak into or pass through it; impermeable if it cannot.
Parts of soilSoil is made from broken-down rock and organic matter, with air and water in the gaps.
Fair test on soilChange only the type of soil, keep the water the same, measure the water collected, and find the mean.
FossilsA fossil is the remains or a trace of something that lived long ago, kept in rock.
How fossils formRemains are buried in sand or mud, layers build up, and the layers are squashed into rock.
Reading layersIn layers that have not been turned over, the bottom layer is the oldest and the top layer is the newest.

Can you…?

  • I can compare rocks by colour, texture, layers, sparkly crystals and holes
  • I can say whether a rock is hard or soft, and whether water can soak into it (permeable)
  • I can name the four parts of soil: broken-down rock, organic matter, air and water
  • I can read the results of a fair test on soil, and say what was changed and measured
  • I can say what a fossil is, and tell remains from traces
  • I can put the stages of fossil formation in order, and read the layers in a diagram

Key terms

rock
a hard, natural material found in the ground
texture
how a rock or soil looks and feels, for example smooth, rough, crumbly or gritty
layer
one flat band of rock or soil, lying on top of or below others
permeable
a material that water can soak into or pass through
impermeable
a material that water cannot soak into or pass through
soil
the layer on top of the ground where plants grow, made from rocks and organic matter
organic matter
dead plants and animals, and their waste, which break down in soil
sediment
sand and mud that settle in layers, often in water
fossil
the remains or a trace of something that lived long ago, kept in rock
body fossil
a part of a living thing kept in rock, such as a bone, a tooth, a shell or a leaf
trace fossil
a sign that a living thing was there, such as a footprint kept in rock
fair test
a test where only one thing is changed, and everything else is kept the same
mean
the average of several results, found by adding them and dividing by how many there are

Exercise 7Z  Check-up

1
Look at the picture. Which sample is soft and white? Write the letter.
ABCDEF
2
Look at the picture. Which sample has sparkly crystals? Write the letter.
ABCDEF
3
Look at the picture. Which sample has holes and lets water soak in? Write the letter.
ABCDEF
4
Write the word for a material that water can soak into or pass through.
5
Name two of the four parts of soil. Write two parts.
6
What is the name for dead plants and animals in soil that break down? Write the words.
7
Look at the table in section 7.4. What is the mean for clay soil? Write the number.
8
Write the word for the remains or traces of something that lived long ago, kept in rock.
9
In layers that have not been turned over, which layer is the newest: the top or the bottom? Write the word.
10
Explain in one sentence how a fossil forms. Write one sentence.

Total 18 marks. Allow about 18 minutes.

Exercise 7X  Practice test questions

1
FLook at the picture of six rock samples. Which sample has holes? Write the letter.
ABCDEF
[1 mark]
2
FWrite the word for water that can soak into a material.[1 mark]
3
FLook at the picture of soil. Write the two things, from the legend, that fill the gaps in soil.
grey dots: broken-down rockbrown shapes: organic matterwhite circles: airblue circles: water
[2 marks]
4
PSA stone soaks up a drop of water in 5 seconds. Is the stone permeable? Write yes or no, and give one reason.[2 marks]
5
RLook at the picture of the three funnels. Which soil let the most water through into its cup? Write the soil, and one reason from the picture.
050100mlsandy soilgarden soilclay soil
[2 marks]
6
FLook at the picture of the five layers. Which layer is the oldest? Write the number.
1Layer 1: top, newest2Layer 23Layer 34Layer 45Layer 5: bottom, oldestnewerolder
[1 mark]
7
FWrite one sentence that says what a fossil is.[2 marks]
8
PSLook at the four pictures of fossil formation, labelled A to D. Write the letters in order, from first to last.
BDAC
[2 marks]
9
RAli says a fossil footprint must have been made by an animal walking today. Is Ali right? Write no, and give two reasons.[3 marks]
10
PSExplain two reasons why plants need soil. Write two reasons.[2 marks]
← Chapter 6: Skeletons and musclesChapter 8: Light and shadows →

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