Question

Heat is produced when water is added to quick lime. Explain the observation.

Answer 1

• The reactions in which heat is produced is known as exothermic reaction.
• The reaction of addition of water $\left({\mathrm{H}}_2\mathrm{O}\right)$ to quick lime $\left(\mathrm{CaO}\right)$ is an exothermic reaction in which Calcium Hydroxide (Slaked lime) $\left(\mathrm{Ca}{\left(\mathrm{OH}\right)}_2\right)$ is produced with a large amount of heat.
• The chemical reaction of quick lime with water is:

$$\begin{gathered} \mathrm{CaO}\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\stackrel{}{\to }\mathrm{Ca}{\left(\mathrm{OH}\right)}_2\left(\mathrm{aq}\right)+\mathrm{Heat} \\ (\mathrm{quick}\mathrm{lime})(\mathrm{slaked}\mathrm{lime}) \end{gathered}$$

• In the above reaction a new substance is formed, hence it is a chemical change.