S3.6.4 For the adult
Physical and chemical changes
Ice melting and wood burning are both changes. Are they the same kind of change?
What this chapter teaches
In a physical change no new substance is made, and it can often be reversed. Melting, boiling and dissolving are examples. In a chemical change atoms join in new ways, a new substance is made, and it is hard to reverse. Gas, heat or light, colour change and a new solid are clues, but only a new substance is proof.
Three questions to ask
There is no one right wording. Listen for the idea.
- Is melting ice a physical or a chemical change? How do you know?
- Why is a colour change not enough to prove a chemical change?
- What happens to the atoms when hydrogen burns to make water?
After the chapter, the learner can
- Sort changes into physical and chemical
- List signs of a chemical change, such as gas, heat or colour
What they copy into their notebook
A physical change makes no new substance. A chemical change makes a new substance. Gas, heat or light, colour or a new solid are clues, not proof.