P Physical change
- The material is <b>rearranged</b>, not replaced.
- Melting · dissolving · tearing · bending · evaporating
- <b>Reversible</b>, because nothing was used up.
- A shattered glass is still glass.
"It is still the same stuff."
C Chemical change
- The old material is <b>used up</b>; new ones appear.
- Burning · rusting · cooking · rotting
- <b>Irreversible</b>, because there is nothing to put back.
- Cooling ash does not make paper.
"Something new exists now."
4 Four signs of a new material
- A colour change that will not wash off
- A gas — bubbles, fizzing, smoke
- Heat or light given off
- A solid appearing in a clear liquid
"What is my evidence?"
↩ Getting it back
- Salt from water — <b>evaporation</b>
- Sand from water — <b>filtering</b> or <b>decantation</b>
- Iron from sawdust — <b>a magnet</b>
- Stones from rice — <b>picking</b>
- Husks from grain — <b>winnowing</b>
"Which method, and what do I lose?"