4. Two important observations of the reaction are:
   • The mixture produces heat and generates steam, indicating an exothermic reaction.
   • The quicklime dissolves in water to form calcium hydroxide (slaked lime), accompanied by the release of heat and the formation of a milky white suspension.

The type of reaction taking place is a chemical reaction, specifically an exothermic reaction, in which quicklime (calcium oxide) reacts with water to form calcium hydroxide (slaked lime) and release heat.

Double bond or double covalent bond: A double bond, also known as a double covalent bond, is a type of chemical bond formed when two atoms share two pairs of electrons. This sharing of electrons results in the formation of a strong bond between the atoms. Examples of molecules containing double bonds include ethene (C2H4) and oxygen (O2).

Triple bond or triple covalent bond: A triple bond, also known as a triple covalent bond, is a type of chemical bond formed when two atoms share three pairs of electrons. This sharing of electrons results in the formation of a very strong bond between the atoms. Examples of molecules containing triple bonds include nitrogen gas (N2) and acetylene (C2H2).

Some elements exist in molecular form because their atoms prefer to share electrons to achieve a stable electron configuration through covalent bonding. Other elements exist in atomic form because they tend to form metallic bonds or ionic bonds, or because they are noble gases with stable electron configurations.