A log gives off heat and light as it burns. A tree stores energy from the Sun in its fruit. A penny lost in the grass slowly changes color. A water pipe freezes and cracks on a cold night.
I gave my students this multiple choice question: Which of the following is an example of a physical change but not a chemical change?

Only one answer is correct among these 4 choices:
- A log gives off heat and light as it burns.
- A tree stores energy from the Sun in its fruit.
- A penny lost in the grass slowly changes color.
- A water pipe freezes and cracks on a cold night.

Could you tell me which one is correct?

A water pipe freezes and cracks on a cold night.