Proof of a Chemical Reaction Example: Sugar + Heat The sugar is in tiny white particles in a pile. Heat is not seen but is implied by the heat source. The pile of sugar in the pot weighs 100 grams. There is a solid, light brown mass at the bottom of the pot. It weighs 100 grams. Yes, both the reactants and the products weigh the same. There was not a chemical reaction. Sugar did not change composition. It only melted. Melting point is a physical property, and this is a physical change. Steel Wool + Oxygen (Fire) Egg + Heat Water + Heat Zinc+ Hydrogen Chloride Sodium Hydroxide + Copper Sulfate