Question

When a chemical change takes place with the evolution of heat energy, the change is said to be_________.

Answer 1

Energy changes in chemical changes: In a chemical change, the molecules and atoms of the substances rearrange themselves to form new substances and involve in energy changes.

• When a change takes place with the evolution of heat energy, the change is said to be exothermic.
• $\mathrm{Reactants}\to \mathrm{Products}+\mathrm{Heat}\mathrm{energy}$
• Example: Combustion of gases is an example of an exothermic change.

Therefore When a chemical change takes place with the evolution of heat energy, the change is said to be Exothermic.