Longitudinal Waves. To see a animations of spherical longitudinal waves check out: In a longitudinal wave the particle displacement is parallel to the direction of wave propagation. The animation at right shows a one-dimensional longitudinal plane wave propagating down a tube.
The boiling point of a substance is the temperature at which the vapor pressure of the liquid equals the pressure surrounding the liquid and the liquid changes into a vapor.
As for vapor pressure being higher at higher temperatures, when the temperature of a liquid is raised, the added energy in the liquid gives the molecules more energy and they have greater ability to escape the liquid phase and go into the gaseous phase.n explanation of vapor pressure. Vapor pressure is constant when there is an equilibrium of water molecules moving between the liquid phase and the gaseous phase, in a closed container.