Pencils down. Let's check the correct classifications together so you know how you went.
| Change | Answer | Why |
|---|---|---|
| Melting butter | Reversible | Same substance — cooling reverses it |
| Toasting bread | Irreversible | New substance — colour & smell change |
| Popping popcorn | Irreversible | Water bursts the kernel — can't undo |
| Ice melt/refreeze | Reversible | Still H₂O the whole time |
| Burning paper | Irreversible | New substances: ash, smoke, gas |