When quicklime (calcium oxide- \(\mathrm{CaO}\) ) is added to water, it reacts vigorously with water to produce slaked lime (calcium hydroxide) and releases a large amount of heat.
The reaction that takes place is:
$$
\mathrm{CaO}+\mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{Ca}(\mathrm{OH})_{2}
$$
Quick lime Slaked lime
The above reaction is an example of combination reaction in which calcium oxide and water combined together to form a single product, calcium hydroxide.
