Solutions and solubility
A solution is a homogeneous mixture at the particle scale. Its particles are evenly dispersed, although they continue moving. Understanding what dissolves, how much can dissolve, and how conditions change solubility lets us prepare and separate mixtures safely.
Learning goals
- Distinguish a solute, a solvent, and a solution.
- Explain dissolving with a particle model.
- Classify solutions as unsaturated, saturated, or supersaturated.
- Read a solubility curve and predict crystallization.
- Separate the rate of dissolving from the amount that can dissolve.
1. Solute, solvent, and solution
The solute is the substance being dissolved. The solvent is the medium that does the dissolving and usually determines the physical state of the solution. The solution contains both. In salt water, salt is the solute and water is the solvent. A solution can also be a gas mixture or a solid mixture; it need not be liquid.
Analogy: imagine many moving seats in a hall. Solvent particles provide the moving surroundings, while solute particles become distributed among them. The solute has not vanished; its particles are simply too small to see individually.