Question

What happens when the temperature of a solution increases?

Answer 1

In chemistry, a solution is said to be a homogeneous mixture of more than two substances in proportional quantities that may vary continuously till the components dissolve completely. While the word "solution" is most often associated with the liquids, solid and gaseous solutions are also available.

Complete answer:
The temperature of any solution means the surrounding temperature at which the solution is present. We must understand that when temperature is associated with a solution, different properties of the solution get involved too. Now the main properties that are affected by any change in temperature are the properties of solubility and kinetic energy present in solutions.
Let us take kinetic energy first;
Every solution consists of molecular particles, so as temperature becomes higher, these molecules tend to move rapidly with great speed. The energy of any moving particle can be considered as its kinetic energy so the molecules gain kinetic energy as there is increase in temperature. So the factor ‘kinetic energy’ increases with the increase in the solution’s temperature.
Next we consider solubility of solution;
In general any substance’s amount (solute) where it will completely dissolve within another substance (solvent) is called the solution’s solubility. We need to understand the change in solubility for solid/liquid solutions and gaseous solutions separately.
- While taking solid/liquid solutions, we see that kinetic energy increases if the temperature is made to go higher. This means that the molecules of the substance in which the solute is dissolved, tend to break the intermolecular attraction between solute particles; as result of which it disintegrates the molecules of the solute. This disintegration of solute particles within the solvent makes it more soluble. So when temperature is higher, higher will be the solubility of liquid/solid solutions.
- Then while taking gaseous solutions (gas in liquids), here again kinetic energy is higher when temperature goes higher, so this causes the intermolecular forces of gas particles (solute) to reduce but here the solute particles are gas particles and they tend to leave from the solvent rather than dissolving in it. The solute will go back to its gaseous form instead of dissolving in the solvent, hence decreasing the solubility of gaseous solutions when the temperature is increased.
Also keep in mind that solid/liquid solutions too can sometimes have less solubility with increase in temperature, this happens when the solid/liquid solutions produce exothermic heat.
Therefore;
Kinetic energy and solubility of liquid/solid solutions increases as temperature is increased, while solubility of gaseous solutions decrease when temperature is raised.

Note:
Just like temperature, another common dependent factor for a solution is pressure. The pressure dependency of solubility in solids and liquids is generally negligibly weak so it is omitted. However, the solubility of gases varies significantly depending on pressure. A gas's solubility usually increases with increasing pressure. Henry's law; can be used to explain this result.