Chemical reactions release or absorb heat or other energy or may produce a gas, odor, color change, or sound. If you don’t see any of these indications, a physical change likely occurred. Be aware a physical change may produce a dramatic change in the appearance of a substance. This doesn’t mean a chemical change occurred. Examples of a chemical change would be rusting iron, or burning wood, or even cooking. Examples of physical changes would be tearing paper, boiling water, or freezing popsicles.
