Final answer:
The addition of water to calcium oxide is a chemical change and an exothermic reaction, resulting in the formation of calcium hydroxide.
Step-by-step explanation:
The addition of water to calcium oxide, also known as quicklime, results in the formation of calcium hydroxide. This is a chemical change because the reaction between solid calcium oxide and liquid water produces solid calcium hydroxide as the only product, indicating the formation of new substances with different properties from the reactants.
Furthermore, this process is not a physical change, nor simply the formation of a mixture, and it's an exothermic reaction since it releases heat to the surroundings, contrary to an endothermic reaction where heat is absorbed.