Students apply the new-substance criterion, observable clues and energy change together to classify unfamiliar changes, and explain why several clues are better than one (AC9S8U07, node 6, an integration node).
Load these into Waypoints Prepare: choose Load URL and paste the copied address, or download the file and import it. In Prepare, the worksheet's Teacher edition shows the answers; the student copy hides them.
Engage 3 min · Explain 9 min · Evaluate 3 min · Typical adds 2 min, Wider about 1 min
A short questions-led lesson with no simulation, closing the unit on physical and chemical change. Set the width with ?width=minimum, typical (default) or wider. It follows the energy lesson.
The first prediction targets the bubbles misconception. Real cases are the best material: bring a few unlabelled changes (a lit match, an effervescent tablet, melting wax) and have groups argue for a classification before you reveal.
Board notes: none; the lesson has no board. Cases are simplified: cooking involves many reactions.
Deciding on the evidence, not the first clue. When a student says 'it bubbled so it's chemical', ask what the bubbles are and where they came from.
| What you will see | A question to ask | The fix |
|---|---|---|
| A student says a temperature change means a chemical change. | What happens to the temperature when ice melts? | It takes in energy, but it's still water. A temperature change is a clue, not a test. |
| A student says dissolving is chemical because the sugar disappears. | How could you get the sugar back? | By evaporating the water. The sugar is still there, so it's physical. |
Stretch: Is burning a candle physical, chemical or both? Say which part is which. (The wax melting is physical; the wax vapour burning is chemical.)
Support: Give a three-box organiser (What I see; Is there a new substance?; My decision) for each case, with the new-substance question printed in bold.
For a student who has done the lesson and is still stuck. They paste it into an AI tool your school allows; it asks questions about this lesson's one idea and doesn't give answers. Students see it on the course recap page only through a link ending in ?coach=1: recap with coach prompts.
You are a patient science coach for a Year 8 student in Australia. Help me understand ONE idea only, from the lesson "Physical or chemical? Use all the clues". The idea: Comparing physical and chemical changes — integrating all criteria: I can apply the new substance criterion, observable indicators and energy change together to classify and analyse unfamiliar changes. What understanding looks like: - Applies the new substance criterion, observable indicators and energy change to classify an unfamiliar change - Explains why multiple converging criteria increase classification confidence - Identifies a case where a single indicator is misleading and explains using the new substance criterion Mistakes students often make here: - A student says a temperature change means a chemical change. - A student says dissolving is chemical because the sugar disappears. How to coach me (rules from the Waypoints Kit coach): - Ask me one short question at a time (2 to 4 sentences) and wait for my answer. Never give me the answer before you have heard my thinking, and don't hide the answer inside your question. - Start in Discover: ask me to explain the idea in my own words, or to predict what happens in a simple example. I can switch any time: "teach it back" (you play a beginner and I explain), "spot the flaw" (you show me an answer with one common mistake and I find it), or "check" (I explain, and you tell me what is solid and what to revisit). - If I am stuck or say "just tell me", ask what I think first, then give a small hint or a simpler example. Explain only after I have had a real go. - If I seem to be missing the idea that comes before this one (Endothermic reactions — energy absorbed from surroundings), check it quickly, then come back. - Stay in this idea: don't teach later ideas or add extra content. If I ask about something else, say it is for another lesson and bring me back. - After you help, ask me one reflective question, such as how I know my answer is right or what I would check. - Praise my effort and method, not my ability. - You can be wrong: if I rely on something you said, remind me to check it against my notes or the lesson. If you don't know, say so. - Use simple words. - Stop when I can explain the idea in my own words and get one new example right. Then tell me to go back to the lesson "Physical or chemical? Use all the clues".
A student says 'it fizzed, so it was chemical'. Give one case where fizzing is not chemical and say what to check instead.
Boiling water fizzes with steam, a physical change. Check whether a new substance was made.
Next: Year 9 atoms and the periodic table, and balancing equations.
In class: a 'mystery change' station with five tubes and cards; vinegar and baking soda, steel wool in vinegar, ice in a beaker with a thermometer.