Describe the arrangement, motion and attraction of particles in a solid, a liquid and a gas, and use them to explain why solids keep their shape and gases fill their containers.
Tip a sugar cube out of its box and it stays a cube. Tip out juice and it spreads across the table. Open perfume and soon the whole room smells. Same particles idea, three behaviours.
The particle model is not just a picture to label. In this lesson you use it to explain what solids, liquids and gases do.
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: a jar of gas
The box has no air in it. Decide before you look.
ExploreTry it on the board and compare what happens with your prediction.
Explore: remove the jar
Choose a state, then remove the jar. Do all three, and watch the particles each time.
Try it yourselfNothing is saved: start again as often as you like.
Remove the jar for the solid, the liquid and the gas.
Use the board. This ticks when you get there.
ExplainUse the particle model to explain what you saw.
Explain: arrangement, motion, attraction
Watch the board while you sort. Every description fits exactly one state.
In your book: explain why juice spreads across a table when a sugar cube keeps its shape. Use arrangement, motion and attraction, not just "because it's a liquid".
Which state does each description belong to?
Particles close together in a fixed pattern
Particles close together with no pattern
Particles far apart
Particles vibrate in place
Particles slide past each other
Particles move fast in all directions
Strong attraction between particles
Weaker attraction: particles stay close but can move
Very weak attraction
Keeps its shape
Spreads across the bottom of its container
Fills its whole container
PractiseA few on your own, to check you have it.
Mix it up
Elaborate TypicalUse the same idea in a new context.
Elaborate: six substances
Try it yourselfNothing is saved: start again as often as you like.
Using the spacing only, where does each substance belong?
Iron (real density 7.87 g/cm³)
Aluminium (2.70 g/cm³)
Water (1.00 g/cm³)
Cooking oil (0.92 g/cm³)
Carbon dioxide (0.0018 g/cm³)
Air (0.0012 g/cm³)
Elaborate WiderUse the same idea in a new context.
Elaborate: heating one substance
Drag the temperature slowly from −20 °C to 120 °C. Watch the motion and the spacing.
Try it yourselfNothing is saved: start again as often as you like.
Heat the water from ice, through liquid, to steam.
Use the board. This ticks when you get there.
Elaborate WiderUse the same idea in a new context.
Elaborate: comparing attraction
To boil, a substance's particles need enough energy to pull completely away from each other. The stronger the attraction, the hotter it has to get.
Put the substances in order of attraction between their particles, strongest first.
Pieces (click to add)
Your program
Elaborate WiderUse the same idea in a new context.
Elaborate: the odd one out, ice
Try it yourselfNothing is saved: start again as often as you like.
EvaluateLook back at your first ideas and what changed.
Evaluate: look back
Where did you think the gas would be? Write one sentence: "At first I thought… Now I think… because…"
Revision summary
Solid: close together, fixed pattern, vibrating in place, strong attraction. It keeps its shape.
Liquid: close together, no pattern, sliding past each other, weaker attraction. It flows and spreads across the bottom of its container.
Gas: far apart, moving fast in all directions, very weak attraction. It spreads to fill its whole container.
A gas spreads in every direction, including down. It is not floating up.
For teachers
Students describe arrangement, motion and attraction for each state and use them to explain why solids keep their shape and gases fill containers (AC9S7U05, node 2, a hinge node). About 25 minutes.
I can describe the arrangement, motion and attraction of particles in a solid, a liquid and a gas.
I can explain why a solid keeps its shape and a gas fills its container.
I can use a particle diagram as evidence in an explanation.
Before class
A concept tutorial for introducing or revising the idea; it does not replace practical work. Set the width with ?width=minimum, typical (default) or wider.
The hinge risk for this node is decorative diagrams: students who label but do not reason with diagrams cannot explain properties in node 3. Push every answer back to a diagram: "show me where that is in the particles".
Running the lesson
Engage: count how many predicted 'the top'. That is the 'gases are light' misconception the jar targets.
Explore: make sure students remove the jar for all three states, not just the gas.
Explain: the 12-item sort is the minimum description. Then the two questions turn description into explanation.
In your own words: collect the juice and sugar cube paragraph; it is the best evidence of the node's checkpoint.
The hard part (on purpose)
Explaining a property from what the particles do, not the state's name. When a student says gas rises because it is light, ask which way the particles moved on the board.
When students get stuck
A student says the gas floats up because it is light. Ask: Which way did the gas particles move on the board? Fix: They moved in every direction, including down. Fast motion and weak attraction spread a gas out.
A student says solid particles don't move. Ask: Look at the solid in the jar for a few seconds. What do the particles do? Fix: They vibrate in fixed positions. Attraction holds them in place; it does not stop them moving.
A student answers 'because it is a liquid' when asked why juice spreads. Ask: What are the liquid's particles doing that makes it spread? Fix: Use the three words: arrangement (close, no pattern), motion (sliding), attraction (weaker).
Stretch and support
Stretch: Air is a gas, yet a room of air doesn't collapse to the floor. Why don't air particles all settle at the bottom like the liquid did?
Support: Give a three-column table (arrangement, motion, attraction) to fill in while watching the board, before the sort.
Where it leads
Next: node 3 explains properties such as compressibility, density and viscosity with the same three features.
In class: a sealed syringe of air, and a perfume or deodorant spray released at the front of the room, timed to when students at the back smell it.
What each step is for
Engage: a jar of gas: Students who think gases rise because they are light will predict the top; the jar shows spreading in every direction.
Explore: remove the jar: Releasing each state from the same jar makes the three behaviours directly comparable.
Explain: arrangement, motion, attraction: Describing each state by all three features, then explaining behaviour from them, is what stops diagrams being decorative.
Mix it up: Bringing back the four key ideas of the particle model, which this lesson uses to explain solids, liquids and gases.
Elaborate: six substances: Ranking substances by spacing, then checking real densities, shows what the model predicts well (the big gaps) and what it needs added (particle mass).
Elaborate: heating one substance: The same particles at different temperatures connect motion and energy to spacing.
Elaborate: comparing attraction: Boiling points are evidence for attraction strength: particles need more energy to pull apart when they attract more strongly.
Elaborate: the odd one out, ice: An anomaly is a chance to evaluate the model: water needs an extra detail, not a new model.
Now you can
Describe the arrangement, motion and attraction of particles in a solid, a liquid and a gas.
Explain why a solid keeps its shape and a gas fills its container.
Use a particle diagram as evidence in an explanation.