Critical Point – the point in temperature and pressure on a phase diagram where the liquid and gaseous phases of a substance merge together into a single phase. Beyond the temperature of the critical point, the merged single phase is known as a supercritical fluid.

Vaporization (or condensation) curve

resulting in a solid with a lower density than the liquid

The Pvap reaches a value that is equal to the atmospheric pressure (Patm). When these two pressures are equal the vapor bubbles quickly rise to the surface because they are less dense than the liquid itself and the liquid is said to be boiling.

vapor pressure of a liquid