Some Changes Cannot Be Undone
- Chemistry
- Ages 6–8 · Grades 1–2
- Hands-on experiment
What you’ll find out
- Some changes, like melting, can be undone by cooling.
- Some changes, like toasting or cooking an egg, cannot be undone.
- When a change cannot be undone, something new has been made.
No sign-up and no real names. In the lesson you check your understanding as you read, run the experiment yourself, and practise until it sticks.
Changes you can undo
Put chocolate on a warm pan and it melts into a runny puddle. Move it somewhere cold and it goes hard again. It is still chocolate, just a new shape. Melting can be undone. Ice works the same way: melt it, then freeze it again.
Changes you cannot undo
Now toast a slice of bread. It turns brown and crunchy. Let it cool down, and it is still toast, not bread. Cook an egg and the clear part turns white and firm. It can never be a raw egg again. The heat made something new, so this change cannot be undone.
Curriculum links: NGSS 2-PS1-4