Evaporation

Evaporation is the process in which a liquid is converted into a vapor. When the substance is in the form of a liquid it is held together by intermolecular forces. As the temperature increases, the molecules pass more forcefully, and augmenting in high proportion has enough sufficient energy to escape from their neighbors. Evaporation as a result is slow at low temperatures yet quick at higher temperatures. In an open vessel, the molecules escape from the vicinity of the liquid and there is net migration from the liquid to the atmosphere.

Liquid to vapor and equilibrium

On the other hand, in a closed vessel net evaporation persists until the number of molecules in the vapor has climbed to the stage at which the rate of return from the vapor to the liquid is the same to the rate of evaporation. At this phase there is a vibrant equilibrium between the liquid and its vapor, with evaporation and its reverse, condensation, happening at the same rate. The pressure of the vapor in the closed vessels is known as the vapor pressure of the substance and its value relies on the temperature. Boiling takes place in an open vessel while the vapor pressure is same to the ambient pressure.

Endothermic process

Evaporation is an endothermic process since molecules must be supplied with energy to overcome the intermolecular forces. The enthalpy of vaporization is the heat needed at regular pressure per mole of substance for vaporization. The entropy of vaporization at the boiling point is equal. According to Trouton’s rule, for many liquids the entropy of vaporization is close to 85J/K. This value reflects the similar alteration in disorder that happens when a liquid is converted into a gas. Nevertheless, certain liquids are more structured than others, and have bigger entropy of vaporization than Trouton’s rule recommends.

Changing into gaseous state

Volatile liquids evaporate more rapidly than others at the same temperature. Such liquids have relatively weak intermolecular forces. In general, the rate of evaporation relies on the strengths of the intermolecular forces and the rate at which heat is supplied to the liquid.

But in simple terms, evaporation can be mean change of a liquid into gaseous state. The process in liquid water comes into the atmosphere as water vapor from such factors like sea, vegetation and replenishes of the humidity of the air. Evaporation is further an essential part of the exchange of the energy in the earth –atmosphere system that produces motion and weather.

Questions:

• What is evaporation?
• State the advantage of evaporation.