Physical and Chemical Changes — AC9S8U07

• Distinguish physical change from chemical change using evidence.
• Recognise gas, precipitate, persistent colour and temperature changes as possible reaction indicators.
• Interpret exothermic and endothermic temperature trends.
• Use before-and-after evidence rather than relying on a single clue.

Recall states of matter, particles, temperature and the distinction between elements, compounds and mixtures from AC9S8U06. Students should know that observations are evidence and conclusions are interpretations of evidence.

A physical change changes state, shape or arrangement without producing a new substance. A chemical change forms new substances with different properties. Use evidence chains rather than “one clue proves it”.

Possible reaction indicators include formation of a new gas, a new solid precipitate, a persistent colour or property change, and a temperature change. Bubbles alone do not prove reaction because boiling is physical; colour alone can change because of mixing or indicators.

In an exothermic reaction, energy is transferred from the reacting system to the surroundings and measured temperature often rises. In an endothermic reaction, the system absorbs energy from surroundings and measured temperature often falls. Applied testing kits—such as soil, water or diagnostic colour tests—use chemical indicators, but every test has limits and needs interpretation.

1. Classify melting ice, rusting iron, burning paper and dissolving salt using evidence.
2. Identify two indicators in a gas-forming, cooling reaction.
3. Interpret a temperature trend that rises from 20°C to 31°C.
4. Explain what extra evidence would strengthen a colour-change conclusion.

1. Explain why rusting is chemical.
2. Explain why melting is physical.
3. Two solutions form a solid. Name the indicator and what it suggests.
4. A reaction mixture becomes colder. Classify the energy change and explain the direction of energy transfer.
5. Explain why a gas bubble from boiling water is not enough evidence for a chemical reaction.
6. Describe one use and one limitation of a soil, water or medical chemical testing kit.

A colourless liquid turns pink after a reagent is added but there is no gas, precipitate or measured temperature change. Explain why “pink means a chemical reaction definitely occurred” is too strong, and identify additional observations or controls that would improve the conclusion.

1. What defines a physical change? No new substance forms; state, shape or arrangement changes.
2. What defines a chemical change? New substances with different properties form.
3. What does an exothermic temperature rise mean? Energy is transferred from the reacting system to surroundings.
4. Why use multiple indicators? Individual observations can have non-chemical explanations, so converging evidence makes the conclusion stronger.

1. A reaction bubbles and cools from 23°C to 16°C. Explain two pieces of evidence and classify the energy change.
   Separate gas evidence from the endothermic temperature trend.
2. Explain why boiling water and acid–carbonate bubbling should not be classified from “bubbles” alone.
   Ask whether a new substance is formed.
3. Evaluate a colour-change testing strip as evidence for water quality.
   Explain what it measures and one factor that limits the conclusion.

• I distinguish physical and chemical change.
• I interpret reaction indicators cautiously.
• I classify exothermic/endothermic trends.
• I build evidence chains.

Exit ticket: Why is “gas + temperature change” usually stronger evidence than “bubbles happened”?

Australian Curriculum v9.0 — AC9S8U07: compare physical and chemical changes and identify indicators of energy change in chemical reactions.

Victorian Curriculum F–10 Version 2.0 — Levels 7–8, VC2S8U08: Exact — distinguishes physical and chemical changes and identifies gas, precipitate, colour and temperature evidence.

NSW Science 7–10 Syllabus (2023) — Stage 4, SC4-CHG-01: Partial — chemical change and energy are related within the Stage 4 Change focus, but the outcome is broader.

• AC9S8U06 — elements, compounds and mixtures
• AC9S8U05 — energy transfers and transformations

• Australian Curriculum v9.0
• Victorian Curriculum F–10 Version 2.0 Science
• NSW Science 7–10 Syllabus (2023)

Curriculum equivalents for Physical and chemical changes and identify indicators of energy change...

Mapped skill: compare physical and chemical changes and identify indicators of energy change in chemical reactions

These references identify matching or closely related learning. Curriculum sequence, terminology and depth vary, so teachers should use the mapped skill and lesson difficulty to confirm suitability.

Australian Curriculum v9.0 is the canonical source for this SkillrHub lesson. Victoria and NSW entries name the closest published state codes or outcomes; international entries are planning references rather than claims of identical curricula.