Particle Models

Overview

This lesson builds on Lesson 1’s introduction to everyday properties of solids, liquids and gases. Students now use a particle model to explain why particles form different arrangements and how this helps us predict observable properties.

Learning intentions

WALT:

• Explain that all matter is made of particles.
• Describe how particles are arranged and how they move in solids, liquids and gases.
• Model solids, liquids and gases using simple particle diagrams.
• Use scientific language to compare particle arrangements.

Success criteria

Students can:

• Draw and label accurate particle diagrams for a solid, liquid and gas.
• Explain (in one or two sentences) how particle spacing and motion differ between the three states.
• Use correct terms such as particle, arrangement, solid, liquid, gas, and move (or motion).

Curriculum links

• AC9S5U04: Explain observable properties of solids, liquids and gases by modelling the motion and arrangement of particles.
• AC9S5I01: Pose investigable questions and make reasoned predictions about relationships between particle arrangement and observable behaviour (used in guided discussion).
• AC9S5I02: Plan and conduct a repeatable investigation (mini demonstration and modelling are repeatable; students record observations consistently).
• AC9S5I06: Communicate ideas and findings using appropriate language and diagrams.
• AC9S5I04: Construct and use representations (tables/visual models) to organise information about particle patterns.

Lesson structure (80 minutes)

1. 0–8 min · Retrieval and hook. Teacher displays three prompt pictures (ice block, water in cup, air in balloon) and asks: “What do you think particles are doing in each?” Students turn-and-talk, then share one idea for each state.

2. 8–18 min · Direct teach: particle model rules. Teacher introduces three “model rules” on the board: particles are too small to see; models are representations; in solids particles are tightly packed, in liquids particles are close but can slide, in gases particles are spread out. Students copy a short “model key” (particle = dot/small circle; spacing shows packing; arrows show motion).

3. 18–32 min · Teacher role-play model (arrangement + motion). Teacher assigns students into three groups and uses their movement to represent particles:

• Solid group: stand close together and stay still (or very slight movement).
• Liquid group: cluster together but shuffle/slide past each other.
• Gas group: spread out across space and move independently. Students observe and record quick notes: “solid: close + mostly still”, “liquid: close + can move past”, “gas: far apart + moving freely”.

4. 32–55 min · Guided drawing: particle diagrams. Students receive a printable template with three boxes (solid, liquid, gas) and a blank space for a short explanation sentence. Teacher circulates using a checklist: correct particle spacing, clear labels, arrows for motion, and the sentence links arrangement/motion to behaviour (e.g., “In a solid, particles are packed closely and mostly stay in place.”). Students refine diagrams after peer feedback from a “diagram partner”.

5. 55–62 min · Quick investigation touchpoint (repeatable observation). Teacher demonstrates: place a drop of food colouring into water (liquid spreads) and show a closed balloon being squeezed slightly (gas compresses). Students discuss which particle model idea best matches what they observed and record one reason on their page. Note: Emphasise observation only; the diagrams must be used to explain, not just describe.

6. 62–75 min · Independent application: “Choose the model” sorting. Students are given 6 mixed particle-diagram cards (some intentionally flawed). In pairs, they sort into “solid model / liquid model / gas model” and justify using one scientific sentence per card set. Teacher checks misconceptions: “gas particles are touching” and “liquid particles are perfectly still”.

7. 75–80 min · Exit ticket. Students complete a one-box exit ticket: draw one particle diagram (chosen by teacher prompts) and add two labels/markers showing arrangement and motion.

Resources

• Particle diagram template (solid, liquid, gas) for each student
• “Particle model rules” mini poster or board key
• Dot/circle particle stickers or printed small circles (optional)
• Role-play space in classroom; clear boundaries for groups
• 6 mixed particle-diagram cards (laminated if possible)
• Checklist for teacher circulation (spacing, labels, motion arrows, link sentence)
• Simple demonstration materials: cup of water, food colouring, balloon, pump or method to squeeze carefully
• Exit ticket slips

Assessment

• Formative checks during role-play notes: students correctly identify arrangement and motion for each state.
• Diagram checklist during guided drawing: teacher monitors spacing, labels and arrows.
• Exit ticket: accuracy of particle diagram plus two-part explanation (arrangement + motion).

Differentiation

• Support:
• Provide sentence starters for the explanation box: “In a ___, particles are ___ and move ___.”
• Offer a partially completed diagram for students needing additional scaffolding (one state fully drawn, others blank).
• Use guided group work: teacher works with a small group to practise placing particles and adding arrows.
• Extension:
• Challenge students to add “what would happen if heat increased?” using arrows or additional labels on the same state diagrams (keep it qualitative).
• Ask advanced students to justify their card sorting using stronger vocabulary (packed, spread, slide, independent).
• EAL / additional needs:
• Pre-teach key words with visuals (particle, arrangement, solid, liquid, gas, move).
• Allow oral explanations to be drafted first, then translated onto the diagram.
• Keep instructions in short steps and display them on the board.