As the temperature of a liquid increases, the solubility
of gases in that liquid decrease. We can use the Second Law of Thermodynamics
to explain why. Heating a solution of a gas enables the particles of gas to
move more freely between the solution and the gas phase. The Second Law
predicts that they will shift to the more disordered, more highly dispersed,
and therefore, more probably gas state.
In a similar way, we can explain why the substances that are
solids at room temperature and pressure tend to become more soluble when the
temperature rises. Heating a solution of a solid makes it easier for the
particles of solid to move between the solution and the solid phase. The Second
Law predicts that they will shift to the more disordered, more highly
dispersed, and therefore, more probably solution state
The second law of thermodynamics: in all energy exchanges,
if no energy enters or leaves the system, the potential energy of the state
will always be less than that of the initial state.
In the case of an exothermic reaction, because energy is
entering the system, the potential energy of the state is more than that of the
initial state.
Because of this, the particles in the gas are more energised
in the warmer solution and thus spread out more, leading to a lesser solubility
of the gas in water.
Along with this, Charles’ law states: For a fixed quantity
of gas at a given temperature, the volume increases linearly with temperature.
Thus the solubility of a gas decreases as the temperature
increases because the volume of the gas increases as temperature increases.
The solubility of a solid in water increases as the temperature of the water increases.