Element 1 is polished to form a smooth surface. Element 2 is heated and evaporates. Element 3 develops a white, powdery surface after standing in air. Element 4 is separated from a mixture by filtration.
I gave my students this multiple choice question: Which is a chemical change?

Only one answer is correct among these 4 choices:
- Element 1 is polished to form a smooth surface.
- Element 2 is heated and evaporates.
- Element 3 develops a white, powdery surface after standing in air.
- Element 4 is separated from a mixture by filtration.

Could you tell me which one is correct?

Element 3 develops a white, powdery surface after standing in air.