Change Detective: Sort the Chaos
Classify changes as physical or chemical.
Setting up the bench…
What this lesson covers
Why it matters
Tear paper and it's still paper. Burn it and you get ash and smoke — gone for good. One change is skin-deep; the other makes something new.
Predict first
What is the sure sign a change is chemical, not physical?
A physical change alters form or state (no new substance). A chemical change makes a new substance — often with heat, light, gas or a colour change.
- A new substance with new properties forms — correct
- The object changes shape
- It simply gets warmer
What you do
Sort each change: physical (same substance) or chemical (new substance)?
Check yourself
Which is a chemical change?
Rusting makes a new substance (iron oxide). Melting and crushing only change form.
Why is dissolving sugar a physical change?
No new substance forms — evaporate the water and the sugar returns.
- Rusting of iron — correct
- Melting wax
- Crushing a can
- The sugar can be recovered unchanged by evaporation — correct
- A new substance forms
- It gives off a gas