What does evaporation achieve in separation processes?

Evaporation is a crucial process in separation techniques, particularly in scenarios where a solute is dissolved in a solvent, creating a solution. By allowing the solvent (the liquid) to evaporate, this process effectively removes the liquid from the solution, leaving behind the solute in solid form. This is particularly useful when the goal is to isolate solid substances from their liquid mixtures.

In more detail, during evaporation, the liquid molecules at the surface gain enough energy to overcome intermolecular forces and transition into the gaseous state. This transition reduces the volume of the liquid phase, leading to a concentration of solute until it crystallizes out or forms a residue. This method is commonly applied in processes such as obtaining salt from seawater or concentrating solutions in chemical laboratories.

The understanding of why evaporation isolates solids from liquids is fundamental in various applications, such as crystallization techniques, where achieving purity is essential.