The shape of the lesson
By the end of the lesson, learners can
- Watch the three states: Switch between solid, liquid and gas and watch how the particle arrangement and motion change.
- Arrangement, motion, behaviour: Each property of a state follows directly from how its particles are arranged and how they move.
- Solid: very close, regular, vibrate in place. Fixed shape and volume.
- Liquid: close, random, move past each other. Fixed volume, takes the shape of its container.
- Gas: far apart, fast and random. Fills the container, easily compressed.
One picture every idea returns to
In a solid, particles are packed closely in a regular pattern and only vibrate. In a liquid they are still close but can slide past one another. In a gas they are far apart and move quickly in all directions. The particles are the same; only their arrangement and motion change.
Forty-five minutes, phase by phase
| Time | Phase | What happens in the room | Grouping |
|---|---|---|---|
| 0 to 5 min | Hook: predict | Open with the question in the title, Same particles, different arrangement.. A block of ice, a puddle and a cloud of steam are all the same water molecules. | Whole class, then pairs |
| 5 to 17 min | Teach and check: Watch the three states | Switch between solid, liquid and gas and watch how the particle arrangement and motion change. Project tab 1 of the lab (States of matter) and let a student drive it while the class predicts. | Whole class, then pairs |
| 17 to 30 min | Teach and check: Arrangement, motion, behaviour | Each property of a state follows directly from how its particles are arranged and how they move. | Think-Pair-Share |
| 30 to 36 min | Check | The four Stage 1 questions from the student lesson, answered on mini whiteboards or by show of fingers. Re-teach the one most get wrong. | Individual, then whole class |
| 36 to 43 min | Plenary | The exam-style questions from Stage 2, one at a time: thirty seconds alone, then a random call. The feedback lines in the key give the examiner's wording. | Individual, random call |
| 43 to 45 min | Exit and homework | Set the worksheet below (6 questions, 14 marks). Learners self-assess against the objectives before they leave. | Individual |
Protect the parts that carry the learning
The sequence carries about fifty minutes of material, so the lab is driven by one student while the class predicts rather than explored freely. Times are a guide.
Protected: the check at 30 minutes. It is the only individual read on whether the key idea landed, and it is not cut.
Cut first if the build overruns: the last check in Arrangement, motion, behaviour, never the check or the plenary.
In a 60 minute block: run worksheet questions 1 to 3 in class as a Rally Coach set and model both the hardest worked example and its check live.
Think-Pair-Share
Pose the question, give thirty seconds of silent thinking, then a minute to compare with a partner before a few pairs share with the class. The silent minute is the part that cannot be cut.
The full structure, with its variations and the other twelve, is on the cooperative-learning page.
What to head off, and how
| Trap learners fall into | Teaching move that pre-empts it |
|---|---|
| The particles themselves do not change between states. | When ice melts or water boils, each molecule is identical before and after; what changes is how close together the particles are, how ordered they are, and how fast they move. |
States of matter (solid, liquid, gas): worksheet
6 questions, 14 marks. Written in the style of the papers; no past paper question is reproduced.
Describe the arrangement and motion of the particles in:
(a) a solid, [1] (b) a liquid, [1] (c) a gas. [1]State whether each property describes a solid, a liquid, or a gas:
(a) has a fixed shape and a fixed volume, [1] (b) has a fixed volume but takes the shape of its container, [1] (c) spreads out to fill any container it is put in. [1]Explain, in terms of particles, why a gas can be compressed into a much smaller volume but a solid cannot.
A solid keeps its own shape, but a liquid flows and takes the shape of its container. Explain this difference in terms of the particles.
When ice melts to water and then boils to steam, a student claims the water particles themselves change. Explain what actually changes and what stays the same.
A small amount of gas is released into a large empty sealed room. Explain, in terms of particle motion, why the gas spreads out to fill the whole room.
Answer key and marking notes
(a) Solid: particles in a fixed, regular, closely packed pattern, vibrating about fixed positions. ✓
(b) Liquid: particles close together but irregularly arranged, able to move past one another. ✓
(c) Gas: particles far apart, moving quickly and randomly in all directions. ✓
(a) Solid. ✓
(b) Liquid. ✓
(c) Gas. ✓
- In a gas the particles are far apart with large spaces between them, so they can be pushed closer together. ✓
- In a solid the particles are already touching with no spare space, so it cannot be compressed. ✓
- In a solid the particles are held in fixed positions by strong forces and can only vibrate, so the shape is fixed. ✓
- In a liquid the particles can move past one another, so the liquid can flow and take the shape of its container. ✓
- The particles themselves do not change, they are the same water particles throughout. ✓
- What changes is their arrangement, spacing, and how freely they move. ✓
- The gas particles move quickly in random directions. ✓
- They travel until they collide with the walls or each other, spreading out until they are evenly distributed throughout the whole room. ✓
2 multiple-choice questions on this lesson
From the topic question bank. Assign them in the app for a marked score in your gradebook, or run the topic as a class game.
Why can a gas be compressed easily but a liquid cannot?
- AThe particles in a gas are far apart with large spaces between them, while liquid particles are already close together.
- BGas particles are smaller than liquid particles.
- CGas particles attract each other more strongly.
- DGas particles move more slowly than liquid particles.
Which state of matter has a fixed volume but takes the shape of its container?
- Asolid
- Bliquid
- Cgas
- Dnone of these
Quiz key
A gas has large gaps between particles, so they can be pushed much closer; a liquid's particles already touch, leaving almost no space to compress. The size of the particles (B) does not change between states.
A liquid keeps a fixed volume but flows to take the shape of its container. A solid keeps both shape and volume; a gas fills the whole container, so its volume is not fixed.
What to project
The student lesson embeds these tabs. Open them full screen on the projector; every slider has a drag handle on the stage.
Slides for this lesson
A projectable deck for every pack is on the way. Until then, present the student lesson full screen: its sections, figure and lab tabs follow the same order as the plan above.