Rocks
KS2SC-KS2-D004
Chemistry/Earth science domain covering classification of rocks, fossil formation and soil composition. Year 3 only. Provides foundation for later work on evolution and inheritance in Year 6.
National Curriculum context
The Rocks domain introduces pupils to the geological materials that make up the Earth's surface, providing a foundation for understanding Earth processes, the rock cycle and the fossil record. Pupils compare and group rocks on the basis of their appearance and physical properties, and learn to distinguish between sedimentary, igneous and metamorphic rocks. The statutory curriculum requires pupils to describe how fossils are formed and understand what they tell us about living things that existed millions of years ago, connecting palaeontology to the concept of evolution. Pupils also study soil, understanding its composition and the role of living organisms and weathering processes in soil formation.
3
Concepts
2
Clusters
3
Prerequisites
3
With difficulty levels
Lesson Clusters
Compare and classify rocks by their appearance and properties
introduction CuratedRock classification and soil composition are linked through the co_teach_hints (C019 and C021) and share the investigative approach of comparing physical properties; soil is formed from weathered rock particles.
Describe how fossils form and what they tell us about the past
practice CuratedFossil formation is a distinct conceptual topic that connects rocks to the history of life; it provides a bridge to KS2 evolution content and is best taught as a focused narrative unit.
Teaching Suggestions (1)
Study units and activities that deliver concepts in this domain.
Rocks and Fossils Classification
Science Enquiry Identifying and ClassifyingPedagogical rationale
Identifying and classifying is an essential science enquiry type that develops observational skills and evidence-based reasoning. Rocks provide a tangible, hands-on context where pupils can handle real specimens, test properties, and connect classroom science to the real landscape around them.
Prerequisites
Concepts from other domains that pupils should know before this domain.
Concepts (3)
Rock Classification
knowledge AI DirectSC-KS2-C019
Understanding that rocks can be grouped and compared based on appearance and physical properties such as grain size, crystal structure, hardness, porosity, and whether they contain fossils. Examples: igneous, sedimentary, metamorphic (informal introduction).
Teaching guidance
Provide a collection of rock samples for hands-on investigation. Test rocks for hardness (scratch test), permeability (water drop test), appearance (crystal/grain examination with hand lens), and reaction to acid (vinegar test for limestone). Use the tests to group rocks rather than simply memorising names. Introduce the three rock types informally: rocks formed from cooled magma (igneous, e.g., granite, basalt), rocks formed from compressed layers (sedimentary, e.g., sandstone, chalk, limestone), and rocks changed by heat and pressure (metamorphic, e.g., marble, slate). Link to local geology where possible.
Common misconceptions
Children often think all rocks are hard and heavy — pumice floats on water, chalk crumbles easily. Some pupils believe rocks are unchanging and permanent, not understanding that rocks are slowly broken down by weathering and reformed over geological time. Children may confuse rocks with minerals, or think that 'sedimentary' means the rock contains mud rather than understanding the process of layers being compressed.
Difficulty levels
Observing and describing the appearance of different rocks, noting visible features like colour, texture and grain size.
Example task
Look at these three rocks. Describe what each one looks like and feels like.
Model response: Rock A is grey and smooth with sparkly bits. Rock B is brown and crumbly with tiny holes. Rock C is dark and shiny with no visible grains.
Testing rocks for simple properties — hardness (scratch test), permeability (water absorption), and appearance — and grouping them based on results.
Example task
Test each rock for hardness (can you scratch it with a nail?), permeability (does it absorb water?) and grain size (can you see individual grains?). Record your results.
Model response: Granite: very hard (nail cannot scratch it), does not absorb much water, visible crystals of different colours. Sandstone: medium hardness (nail scratches it slightly), absorbs water, visible sand grains. Chalk: soft (nail scratches it easily), absorbs lots of water, no visible grains — smooth and powdery.
Grouping rocks based on properties and beginning to understand that the three rock types (igneous, sedimentary, metamorphic) form in different ways.
Example task
Group these rocks by how they were formed: granite (cooled from melted rock underground), sandstone (layers of sand pressed together), marble (limestone changed by heat and pressure). What are the three rock types called?
Model response: Granite is igneous — formed when melted rock (magma) cooled slowly underground, which is why it has large crystals you can see. Sandstone is sedimentary — formed when layers of sand were squashed and cemented together over millions of years, which is why you can see the grains and sometimes find fossils in it. Marble is metamorphic — formed when limestone was changed by intense heat and pressure, creating a hard, crystalline rock. The three types are igneous (from heat), sedimentary (from layers) and metamorphic (from change).
Explaining how rock properties relate to formation processes, and using properties to identify an unknown rock's likely type.
Example task
I give you an unknown rock. It has visible layers, contains small shell fossils, and absorbs water when you drip on it. What type of rock is it likely to be? How do you know?
Model response: It is almost certainly sedimentary. The visible layers show it formed from material deposited in layers over time. The fossils prove it was once soft enough for organisms to be trapped in it — only sedimentary rocks typically contain fossils because igneous rocks form from hot molten material that would destroy organisms, and metamorphic rocks are changed by such intense heat and pressure that fossils are usually destroyed. Absorbing water means it is porous — sedimentary rocks often have gaps between their grains. Using multiple properties (layers, fossils, porosity) together gives a much more reliable identification than any single test alone.
Delivery rationale
Science knowledge concept — factual content deliverable with visual representations and adaptive quizzing.
Fossil Formation
knowledge AI DirectSC-KS2-C020
Understanding in simple terms how fossils are formed when the remains or traces of living things are trapped within sedimentary rock over millions of years. Fossils provide evidence of past life on Earth.
Teaching guidance
Use a layered modelling activity to demonstrate fossil formation: press plastic animals or shells into soft clay or plaster of Paris, then layer 'sediment' on top. Discuss the timescale — millions of years — and why only hard parts (bones, shells, teeth) typically fossilise. Examine real or replica fossils and ask pupils to identify which living things they came from. Discuss Mary Anning's contributions to palaeontology as a historical case study. Link fossil evidence to the concept that Earth has changed over time and that organisms that lived long ago may differ from those alive today.
Common misconceptions
Children often think fossils are the actual bones of the animal rather than mineralised replacements or impressions in rock. Some pupils believe dinosaur bones are found complete and assembled, rather than as scattered fragments requiring reconstruction. Children may not grasp the immense timescales involved — they tend to underestimate geological time by orders of magnitude.
Difficulty levels
Knowing that fossils are the remains of animals or plants from long ago that are found in rocks.
Example task
What is a fossil? Where might you find one?
Model response: A fossil is the remains of an animal or plant that lived a very long time ago. You find fossils inside rocks.
Describing in simple terms how a fossil forms: an organism dies, is buried by sediment, and its remains are slowly replaced by minerals over millions of years.
Example task
Describe how a dinosaur fossil might have formed. Use the words: died, buried, sediment, minerals, millions of years.
Model response: A dinosaur died and fell to the ground near a river. Its body was quickly covered by layers of sediment like sand and mud. Over millions of years, more layers built up on top. Very slowly, minerals from water seeped into the bones and replaced them, turning them to stone. The surrounding sediment also hardened into rock. That is how we find dinosaur bones inside rock today.
Explaining the fossilisation process, why only some organisms fossilise (hard parts, rapid burial), and why fossils are found only in sedimentary rock.
Example task
Why are most fossils of bones, shells and teeth rather than soft body parts? Why do we not find fossils in volcanic rock?
Model response: Hard parts like bones, shells and teeth fossilise best because soft parts (skin, muscles, organs) decay quickly before they can be preserved. The organism must be buried rapidly — by sediment from a flood or river — before scavengers and decomposers destroy the remains. Fossils are found in sedimentary rock because this forms from layers of sediment that can trap and preserve remains. Volcanic (igneous) rock forms from hot molten magma, which would destroy any organisms. That is why palaeontologists look in sedimentary rock formations to find fossils.
Explaining how fossils provide evidence about past environments and the history of life on Earth, linking to the concept of extinction.
Example task
Fossils of tropical plants have been found in Antarctica. What does this tell us about Earth's history?
Model response: Finding tropical plant fossils in Antarctica tells us that Antarctica was once much warmer than it is today — warm enough for tropical plants to grow. This could be because Earth's climate was warmer globally, or because the continent was in a different position closer to the equator (continental drift). This is powerful evidence because fossils preserve a record of what lived in a place millions of years ago. It shows that Earth's environments have changed dramatically over geological time. Fossils are like windows into the past — they tell us about ancient climates, extinct species, and how the planet has changed. Without fossils, we would have no way of knowing that Antarctica was once tropical.
Delivery rationale
Science knowledge concept — factual content deliverable with visual representations and adaptive quizzing.
Soil Composition
knowledge AI DirectSC-KS2-C021
Understanding that soils are made from rock particles (formed by weathering) and organic matter (decayed living material). Different soils have different properties depending on their rock and organic matter composition.
Teaching guidance
Collect soil samples from different locations around the school grounds and compare them. Shake soil in water to separate layers — gravel sinks first, then sand, then silt, with organic material floating. Use hand lenses to examine soil closely and identify fragments of rock, decayed leaves, roots and small organisms. Discuss how soil forms from the breakdown of rocks (physical and chemical weathering) combined with decomposed plant and animal material. Connect to the rock cycle and the role of living organisms (earthworms, fungi, bacteria) in soil formation.
Common misconceptions
Children often think soil is just 'dirt' with no particular composition or structure. Some pupils believe soil has always existed and do not connect it to the breakdown of rocks. Children may not realise that soil contains living organisms — bacteria, fungi, worms — that are essential for its formation and fertility. Some pupils think all soils are the same, not recognising that different soils have different properties.
Difficulty levels
Knowing that soil is found on the ground and that plants grow in it.
Example task
What is soil? Why do gardeners need it?
Model response: Soil is the brown, crumbly stuff on the ground. Plants grow in soil because their roots go into it to get water.
Describing soil as a mixture of tiny rock pieces and decayed plant and animal material (organic matter).
Example task
What is soil made from? Name two things you would find in a handful of soil.
Model response: Soil is made from tiny pieces of rock that have broken down over time, mixed with decayed leaves and other organic matter. You might also find small roots, worms and other tiny living things.
Explaining that soil forms from weathered rock mixed with organic matter, and that different soils have different properties depending on their composition.
Example task
We shook three different soils in jars of water and left them overnight. The layers settled differently. What does this tell us?
Model response: The layers show the different components of each soil. The bottom layer is heavy sand and gravel (rock particles), the middle layer is finer silt, and floating material on top is organic matter (decayed plants). Sandy soil had a thick bottom layer — it drains quickly but does not hold nutrients well. Clay soil had a thick middle layer — it holds water but can become waterlogged. Garden soil had a good mix of all layers plus lots of organic matter — this is why it is good for growing plants.
Explaining the rock cycle connection to soil formation and the role of living organisms in creating and maintaining healthy soil.
Example task
How do rocks become soil? What role do worms and other organisms play?
Model response: Rocks break down into soil through weathering — water gets into cracks and freezes, expanding and splitting the rock. Rain dissolves some minerals. Plant roots grow into cracks and push them apart. Over thousands of years, rocks crumble into smaller and smaller pieces. But rock particles alone are not good soil — living organisms are essential. Worms mix organic matter through the soil, create air channels, and their waste is rich in nutrients. Bacteria and fungi decompose dead leaves and animal remains into humus, which holds water and nutrients. A teaspoon of healthy soil contains billions of micro-organisms. Without these living things, soil would just be crushed rock — it would not support plant growth.
Delivery rationale
Science knowledge concept — factual content deliverable with visual representations and adaptive quizzing.