A liquid begins to boil when?

A liquid begins to boil when its vapor pressure equals the atmospheric pressure. Boiling is the process by which a liquid changes its state to gas or vapor by heating it. When a liquid is heated, its temperature increases and its molecules gain kinetic energy, resulting in the increased movement of its particles. As a result, the vapor pressure of the liquid also increases. When the vapor pressure of the liquid equals the atmospheric pressure, the liquid starts boiling, and its molecules start escaping from its surface in the form of gas or vapor. This is a physical change in the state of matter from a liquid to a gas.