Here's a problem to solve: Which is a chemical change?

Among the 4 following options, which is the correct answer?

- A: Element 1 is polished to form a smooth surface.
 
- B: Element 2 is heated and evaporates.
 
- C: Element 3 develops a white, powdery surface after standing in air.
 
- D: Element 4 is separated from a mixture by filtration.
 