Students list observable signs of chemical change and explain that each is a clue to a new substance, not proof, distinguishing misleading signs in physical changes (AC9S8U07, node 3).
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 and Explore 7 min · Explain 9 min · Evaluate 3 min · Typical adds 3 min, Wider about 2 min
A concept tutorial for introducing or revising the idea; it is best paired with a circus of quick reactions (vinegar and bicarb, lead-free precipitates, steel wool burning). Set the width with ?width=minimum, typical (default) or wider. It follows Is it a new substance? (node 2) and comes before Hotter or colder? (nodes 4 and 5).
Not a hinge node. Students tend to treat any one sign as proof; the prediction and the "clue or trap" sort target it.
Board notes: the board can't show colour, smell or a precipitate; it shows new particles and the temperature change. The dissolve board shows a case with no sign at all.
Holding 'clue' and 'test' apart. When a student says 'it bubbled, so it reacted', ask what is inside the bubbles before agreeing.
| What you will see | A question to ask | The fix |
|---|---|---|
| A student says boiling is a chemical change because of the bubbles. | What are the bubbles made of? | Steam: water particles. No new substance, so physical. |
| A student says any colour change means a reaction. | What happens when you mix blue and yellow paint? | It looks green, but both paints are still there. A colour change is a clue, not proof. |
One possible solution for each task. Other correct programs are fine.
Open task: any program that does what the step asks.
Open task: any program that does what the step asks.
Stretch: Why is 'it can't be reversed' a poor test for a chemical change? (Some physical changes are hard to reverse, like shattering a glass; some reactions can be reversed, like charging a battery.)
Support: Give the signs as picture cards (bubbles, colour, cloudy solid, flame, thermometer, nose) to sort into 'sign' and 'proof needed'.
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 "How can you tell a reaction happened?". The idea: Observable indicators of chemical change: I can identify and explain four observable indicators of chemical change and explain why each suggests a new substance has formed. What understanding looks like: - Names four observable indicators of chemical change - Explains why each indicator suggests a new substance has formed - Distinguishes indicators (observable evidence) from the definition (new substance) Mistakes students often make here: - A student says boiling is a chemical change because of the bubbles. - A student says any colour change means a reaction. 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 (Chemical change — new substance formation at the particle level), 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 "How can you tell a reaction happened?".
Bicarb and vinegar fizz and the mixture gets colder. Name two signs of a chemical change, and say what would prove it.
Gas given off (fizzing) and a temperature change. A new substance would prove it (carbon dioxide, which turns limewater cloudy).
Next: Hotter or colder? (exothermic and endothermic, nodes 4 and 5). Comparing physical and chemical changes with all the criteria (node 6) is a class task.
In class: a reaction circus with an observation table (what you saw, which sign, new substance?).