Question

Define melting and vaporisation.

Answer 1

In order to answer this question, we will explain melting first and we will also explain the mechanism and the properties of melting. And then we'll talk about the vaporisation process and their phenomena.

Complete answer:
Melting, or fusion, is a physical process that results in the phase transition of a substance from a solid to a liquid. This occurs when the internal energy of the solid increases, typically by the application of heat or pressure, which increases the substance's temperature to the melting point.
Substances in the molten state generally have reduced viscosity as the temperature increases. An exception to this principle is the element sulphur, whose viscosity increases in the range of $160\;^\circ C{\text{ }}to{\text{ }}180\;^\circ C$ due to polymerization.
Vaporisation of an element or compound is a phase transition from the liquid phase to vapour. There are two types of vaporization: evaporation and boiling. Evaporation is a surface phenomenon, whereas boiling is a bulk phenomenon. A laboratory flask filled with pure bromine, a liquid that evaporates rapidly.
Evaporation is a phase transition from the liquid phase to vapour (a state of substance below critical temperature) that occurs at temperatures below the boiling temperature at a given pressure. Evaporation occurs on the surface. Evaporation only occurs when the partial pressure of vapour of a substance is less than the equilibrium vapour pressure. For example, due to constantly decreasing pressures, vapour pumped out of a solution will eventually leave behind a cryogenic liquid.

Note:
- Now one question arises here, how heat can affect the evaporation process? So, Heat must be supplied to a solid or liquid to effect vaporization. If the surroundings do not supply enough heat, it may come from the system itself as a reduction in temperature.