States of Matter Basics

Overview

In this first lesson of the unit, students introduce solids, liquids and gases and link their observable properties to a simple particle-model explanation. Students classify everyday materials through hands-on sorting and justify their choices using property-based observations.

Learning intentions

• WALT define solids, liquids and gases using observable properties.
• WALT explain observable properties of solids, liquids and gases by modelling the motion and arrangement of particles.
• WALT classify materials into the correct state using evidence from their observations.

Success criteria

Students can:

• I can describe how solids, liquids and gases behave (shape/volume and movement).
• I can sort materials correctly into solids, liquids and gases.
• I can give a reason for my classification using an observable property (e.g. “it keeps its shape”, “it spreads to fill the container”, “it compresses/doesn’t have a fixed shape”).

Curriculum links

• AC9S5U04: explain observable properties of solids, liquids and gases by modelling the motion and arrangement of particles.
• AC9S5I01 (as appropriate): pose investigable questions and make reasoned predictions (e.g. predicting which state fits a description).
• AC9S5I02 (as appropriate): plan and conduct repeatable investigations using fair-test thinking (e.g. consistent tests for sorting).
• AC9S5I04 (as appropriate): use representations such as a table to organise classification data.
• AC9S5I05 (as appropriate): compare results to class reasoning and identify possible sources of error (e.g. “we didn’t test it the same way”).

Lesson structure (80 minutes)

1. 0–8 min · Hook & discussion. Teacher shows three items (e.g. a block of modelling clay, a sealed water bottle, and an inflated balloon) and asks, “What do you notice that looks the same and what looks different?” Students think-pair-share and contribute 1–2 observations to a class list.

2. 8–18 min · Direct teach: define the states. Teacher introduces definitions using observable behaviours: solids keep shape, liquids flow and take the container’s shape, gases spread to fill the space and can be compressed. Students copy a simple organiser: Solid / Liquid / Gas with two key observable properties for each.

3. 18–30 min · Particle model mini-role-play. Teacher sets up a quick, physical model: “particles” as students in zones (tight, close together for solids; sliding past for liquids; far apart, moving freely for gases). Students act the movement and arrangement, then link it to observable behaviour using teacher prompts (“How does this explain shape?” “What would happen if you squeeze?”).

4. 30–45 min · Sorting investigation (station activity). Teacher explains students will classify mystery materials using consistent tests: observe shape, pour/flow behaviour, and compressibility indicators (e.g. syringe air vs. solid objects, or squeezing a balloon/pouch). In small groups, students test and sort items onto three cards: Solid / Liquid / Gas. They record a short justification for each item in a group table.

5. 45–60 min · Whole-class evidence check. Teacher selects 4–6 items for discussion. Students defend their placement using property evidence. Students vote, then revise if needed, and add a “why” sentence to their table (e.g. “It was a liquid because it spread to fill the cup”).

6. 60–70 min · Error spotting & clarification. Teacher guides a brief reflection: “Where could our sorting be wrong? What test did we not do, or do differently next time?” Students identify at least one possible source of error (e.g. steam vs. water, containers affected shape, not waiting for settling).

7. 70–80 min · Exit ticket & feedback loop. Teacher distributes a short exit ticket with three prompts: (1) “Name one property that helps identify a solid.” (2) “Circle the best reason a gas is a gas.” (A: keeps shape / B: spreads to fill space / C: can be poured like sand) (3) “Explain your particle-model idea in one sentence.” Students complete independently; teacher collects for quick assessment.

Resources

• 3 sorting cards (Solid/Liquid/Gas) and a class display chart
• Object set (per groups): solid items (e.g. eraser, paperclip), liquids (e.g. water in small cups, oil in a dropper bottle), gas indicators (e.g. balloon, sealed syringe with air, plastic bag inflated and tied)
• Mystery material cards with pictures/names (optional)
• Group recording sheet (table with columns: Material, Observed properties, State, Reason)
• Safety equipment: goggles (if syringes/balloons used), paper towels
• Teacher particle-model prompt cards (tight/slide/free)
• Exit ticket slips and pens
• Short educational video on states of matter: https://www.youtube.com/watch?v=ELchwUIlWa8

Assessment

• Formative during stations: teacher checks group records and asks “What did you observe?” and “How does that link to particles?”
• Formative during whole-class evidence check: listens for correct property-based justifications, not just guesses.
• Exit ticket (70–80 min): checks ability to define and classify, plus a simple particle-model explanation.

Differentiation

• EAL support: provide sentence starters (“I think it is a liquid because…”, “The particles are…”); include picture cards showing shape/flow/spread; allow responses orally or with drawing.
• Visual supports: show “before/after” images for pouring and balloon squeezing; use colour-coded sorting categories.
• Hands-on support: pre-assign roles in groups (tester, recorder, speaker) and ensure every student handles at least one material.
• Scaffold recording: offer a partially completed table template for students needing structure.
• Extension for advanced learners: challenge students to find an extra everyday example for each state (including tricky ones like foam, steam, and mist) and write one testable observation question they could investigate next lesson (e.g. “Does steam take the shape of its container?”).

Extension (optional)

• Students research and record one additional example of each state of matter (solid, liquid, gas) and bring back a short note describing the observable property that supports their classification.