When ammonium chloride dissolves in water, the solution becomes colder. (b) Why does the solution form?

Key Concepts

Dissolution Process

The dissolution process involves the breaking apart of solute particles and their interaction with solvent molecules. In the case of ammonium chloride (NH4Cl), when it dissolves in water, the ionic bonds between the ammonium and chloride ions are broken, allowing them to disperse throughout the water. This process requires energy, which is absorbed from the surroundings, leading to a decrease in temperature.

Endothermic Reactions

An endothermic reaction is a chemical process that absorbs heat from its surroundings. The dissolution of ammonium chloride in water is an example of this type of reaction, as it requires energy to break the ionic bonds and separate the ions. As a result, the surrounding water loses heat, causing the temperature of the solution to drop.

Thermodynamics of Solutions

Thermodynamics in the context of solutions refers to the energy changes that occur during the mixing of solutes and solvents. The overall energy change during dissolution is determined by the balance between the energy required to break solute-solute and solvent-solvent interactions and the energy released from solute-solvent interactions. In the case of ammonium chloride, the energy absorbed during dissolution exceeds the energy released, resulting in a colder solution.