Question

question 21
which of the following is an example of a physical change?
grinding coffee beans
baking a cake
converting water to hydrogen and oxygen
burning coal

Explanation:

A physical change alters the form or appearance of a substance without changing its chemical composition. Grinding coffee beans only changes their physical form from whole beans to powder. Baking a cake involves chemical reactions between ingredients. Converting water to hydrogen and oxygen is a chemical decomposition reaction. Burning coal is a combustion reaction, a chemical change.

Answer:

grinding coffee beans