Vaporization and solidification of liquids

1.
Vaporization of liquids

There are two ways to vaporize liquid: evaporation and boiling
.

The vaporization of a liquid is only carried out on the surface of the liquid, which is called evaporation; the vaporization of a liquid is carried out on the surface and inside of the liquid at the same time, which is called boiling.

Sometimes, when the liquid is heated to the boiling temperature, the liquid does not boil.
This phenomenon is called overheating
.

Overheating often causes the temperature to be too high and the liquid bumps, which is very dangerous

2.
Saturated vapor pressure

1) Saturated vapor pressure of pure solvent

In a closed container, when the condensation rate of pure solvent molecules is equal to the evaporation rate, the system reaches dynamic equilibrium and the vapor pressure does not change.
At this time, the vapor is saturated vapor, and the pressure generated is called the saturated vapor pressure at that temperature.
, Represented by the symbol p*
.

The saturated vapor pressure is related to the temperature, and the saturated vapor pressure increases as the temperature rises
.

For example, the saturated vapor pressure of water at 20°C is 2338Pa, the saturated vapor pressure of water at 25°C is 3167Pa, and the saturated vapor pressure of water at 30°C is 4242Pa

2) The saturated vapor pressure of the solution

The vapor pressure when the number of molecules condensed on the surface of the solution is equal to the number of vaporized molecules per unit time is called the saturated vapor pressure of the solution
.

When the non-volatile solute is dissolved in the solvent to form a solution, part of the surface of the solution is occupied by the solute
.

Therefore, the number of solvent molecules evaporated on the surface of the solution per unit time is less than the number of molecules evaporated by a pure solvent, and the density and pressure of the vapor at equilibrium are both lower than that of a pure solvent

Figure 1-1 Saturated vapor pressure-temperature diagram
l ₁ -the saturated vapor pressure of pure solvent;
l ₂ -the saturated vapor pressure of solution

3) Raoult's law

According to a large number of experimental results, Raoult concluded that at a certain temperature, the saturated vapor pressure p of a dilute solution is equal to the product of the saturated vapor pressure p* of the pure solvent and the mole fraction of the solvent in the solution x _agent .

3.

Solidification of liquids

Solidification of the liquid crystals during the solidification temperature is constant, this temperature is called the freezing point, with T _F expressed
.

At this temperature the saturated vapor pressures of the liquid and solid are equal

Related link: Concentration of solution