Question

Describe Evaporation in Detail !

Answer 1

Evaporation is a gradual transition from liquid to gaseous state. This phenomenon is therefore a progressive vaporization which has the effect of absorbing calories and therefore reducing the temperature of the environment.


When there is a free volume above a liquid, a fraction of the molecules composing the liquid is in gaseous form. At equilibrium, the amount of gaseous material defines the saturating vapor pressure in the case of a pure liquid (solvent), which depends on temperature. This pressure may be partial or total.

When the partial pressure of the vapor in the gas is lower than the saturating vapor pressure, some of the molecules pass from the liquid phase to the gas phase: evaporation, which requires the corresponding latent heat, Cools the liquid. This phenomenon is described by the Hertz relation.

The equilibrium is characterized by the simultaneous equality of the partial pressure and the saturating vapor pressure of the liquid on the one hand, and temperatures on the other hand (at equilibrium, The balances of the heat and material fluxes are zero, the masses and the temperatures are constant).

When the solvent is not pure, the solvent and solute bonds decrease the vapor pressure in equilibrium with the condensed or adsorbed phase, the equilibrium being always defined by a zero flux (heat and material): otherwise, The vapor pressure in equilibrium is no longer necessarily saturated in this case. This is called a decrease in solvent activity.

Answer 2

evaporation is a process of changing of water molecules to vapour at any tmperature is known as evaporation.it is very useful to us. by evaporation of water from seas we get rain.evaporation is also known as cooling process. when we feel hot we get sweat . the sweat evaporates so we feel cool......