All matter is made of tiny particles with empty space between them, always moving and attracting each other. Match particle diagrams to solids, liquids and gases.
Water looks smooth and continuous. Zoom in about a billion times and the picture changes completely: that picture is the particle model, and the rest of chemistry is built on it.
Scientists explain how substances behave with a model: a simplified picture that is good at explaining and predicting. This lesson builds the particle model and its four key ideas.
Engage: Commit to a prediction before you test anything. A wrong guess is fine: it shows you what to look for.
Explore: Try it on the board and compare what happens with your prediction.
Explain: Use the particle model to explain what you saw.
Practise: A few on your own, to check you have it.
Elaborate: Use the same idea in a new context.
Evaluate: Look back at your first ideas and what changed.
WidthMore contexts, same idea.
Make your prediction first. Help opens once you've locked it in.
EngageCommit to a prediction before you test anything. A wrong guess is fine: it shows you what to look for.
Engage: zoom into a drop of water
Decide before you look. There is no penalty for being wrong: the point is to find out what you think now.
ExploreTry it on the board and compare what happens with your prediction.
Explore: the zoom lens
Look at each sample for a few seconds. Watch how the particles are spaced, and how they move.
Try it yourselfNothing is saved: start again as often as you like.
Look at all three samples: ice, liquid water and steam.
Use the board. This ticks when you get there.
ExplainUse the particle model to explain what you saw.
Explain: what the model says
Look at any sample. What fills the gaps?
Watch the ice sample closely.
Think about what changed between the three samples, and what did not.
Sort each statement.
Compare the three samples on the board.
Which statements are part of particle theory?
All matter is made of tiny particles.Key idea 1.
There is empty space between particles.Key idea 2.
Particles are always moving.Key idea 3. Even in solids they vibrate.
Particles attract each other.Key idea 4. Strongest in solids, weakest in gases.
Particles expand when they are heated.Particles never change size. They move faster and spread out.
There is air between the particles.Air is made of particles too.
Particles in a solid do not move.They vibrate in place.
Match each state to its particles: arrangement, motion and attraction.
Solid
Liquid
Gas
PractiseA few on your own, to check you have it.
Name that state
Each round shows a new substance through the zoom lens. Is it a solid, a liquid or a gas?
Try it yourselfNothing is saved: start again as often as you like.
Name the state of six substances correctly.
Use the board. This ticks when you get there.
Elaborate TypicalUse the same idea in a new context.
Elaborate: explain three things about ice
On paper: draw a particle diagram of ice and label it with these three explanations.
For each property of ice, choose the particle explanation.
Ice keeps its shape on a plate.Strong attraction holds each particle in place.
You can't squash an ice cube.There is almost no empty space to push the particles into.
An ice cube held in your hand starts to melt.Warming makes particles vibrate more until they slide past each other.
Elaborate WiderUse the same idea in a new context.
Elaborate: build a state
Choose how close the particles are and how they move. Try the combinations that don't make a real state too, and read what the board says.
Try it yourselfNothing is saved: start again as often as you like.
Build a solid, a liquid and a gas.
Use the board. This ticks when you get there.
Elaborate WiderUse the same idea in a new context.
Elaborate: how good is the model?
Does the particle model explain it?
Why a gas spreads to fill its containerGas particles move fast in all directions.
Why you can smell perfume from across a roomPerfume particles move and spread between the air particles.
Why copper is orange-brownColour depends on what the particles are made of.
Why solids keep their shapeStrong attraction holds particles in place.
What particles themselves are made ofThe model treats particles as tiny balls. Atoms come later.
Why some substances are poisonousThat depends on chemistry, not on arrangement or motion.
Elaborate WiderUse the same idea in a new context.
Elaborate: designing with materials
Match each design choice to the particle reason.
Bike tyres are filled with air, not water.Air particles have space to move closer when you hit a bump.
Car brakes use a liquid in the pipes to push the brake pads.A gas would just squash.
Bridge beams are made of solid steel.Strong attraction keeps the steel particles in place.
EvaluateLook back at your first ideas and what changed.
Evaluate: look back
Go back to your prediction in Engage. Was matter smooth, drops, particles in water, or particles with empty space? Write one sentence: "At first I thought… Now I think… because…"
Revision summary
All matter is made of tiny particles; there is empty space between them; they are always moving; they attract each other.
Solid: close together in a fixed pattern, vibrating in place.
Liquid: close together with no pattern, sliding past each other.
Gas: far apart, moving fast in all directions.
There is nothing between particles: not air, not water.
For teachers
Students build the particle model's four key ideas (particles, space, motion, attraction) and match particle diagrams to solids, liquids and gases (AC9S7U05, node 1, a hinge node). About 25 minutes.
I can state the four key ideas of particle theory.
I can match a particle diagram to a solid, a liquid or a gas.
I can describe how arrangement and motion differ between the three states.
Before class
This is a concept tutorial for introducing the model or revising it, not a replacement for the practical. Run it before hands-on work with states (melting ice, a sealed syringe of air). Set the width in the link you share: ?width=minimum, ?width=typical (the default) or ?width=wider. Students can widen but not narrow.
The node's response mode is consolidation, so the Practise step (six correct identifications, with feedback naming the particle feature each time) is part of the minimum path.
Running the lesson
Engage: students lock in a prediction before the zoom lens opens. Ask who chose 'particles floating in water' and why; it is the most common answer.
Explore: insist they watch the ice for a few seconds. 'Frozen still' is the misconception the second Explain question targets.
Explain: the four key ideas are the hinge. Have students say them aloud in order: particles, space, motion, attraction.
Practise: six correct, not six in a row. Listen for students naming a feature, not just a state.
Evaluate: the 'At first I thought… Now I think…' sentence is worth collecting as an exit card.
The hard part (on purpose)
Accepting empty space between particles, with nothing in it. When a student puts air between the particles, ask what air is made of.
When students get stuck
A student says there is air between the particles. Ask: What is air made of? Fix: Air is particles too. Between any particles there is nothing at all: empty space.
A student labels a liquid diagram as a solid because the particles touch. Ask: Is there a pattern? Do the particles stay in place? Fix: Solids and liquids are both close together. The difference is the fixed pattern and the motion.
A student says particles get bigger when heated. Ask: In the zoom lens, did any particle change size between ice and steam? Fix: Particles never change size; the spaces between them do.
Stretch and support
Stretch: Why can't particles that are far apart stay still? Use the Build a state board to argue it.
Support: Give students the four key ideas on a card for the Practise step, and ask them to point to the feature they used each time.
Where it leads
Next: node 2 uses the diagrams to reason (why gases fill containers, why solids keep their shape). Node 3 explains properties such as compressibility and density.
In class: follow with real samples (an ice cube, water, a sealed syringe of air) and ask students to draw the particle view of each.
What each step is for
Engage: zoom into a drop of water: Committing to a picture of matter first exposes the idea that matter is continuous, or that particles float in something.
Explore: the zoom lens: Seeing ice, water and steam as the same particles in different arrangements sets up the whole model.
Explain: what the model says: The four key ideas (particles, space, motion, attraction) are what students must be able to reproduce before they can use diagrams to reason.
name that state: Reliable matching of diagrams to states needs practice with feedback that names the particle feature every time.
Elaborate: explain three things about ice: Explaining properties in particle language is the move from describing the model to using it.
Elaborate: build a state: Spacing and motion go together: building the states from the two features shows why some combinations never happen.
Elaborate: how good is the model?: Every model has limits; Brownian motion is the classic evidence that particles exist and move.
Elaborate: designing with materials: Designers in Design and Technologies choose solids, liquids and gases for exactly these particle reasons.
Now you can
State the four key ideas of particle theory.
Match a particle diagram to a solid, a liquid or a gas.
Describe how arrangement and motion differ between the three states.