Key Terms
- Solution: a homogeneous (uniform) mixture of a solute and a solvent.
- Solvent: the majority component of a solution, which dissolves the other.
- Solute: the minority component, which is dissolved.
- Aqueous solution: a solution whose solvent is water.
- Saturated solution: a solution that cannot dissolve any more solute at a given temperature.
Experiment: Preparing a Saturated Solution
Requirements: test tube, spatula, common salt, glass rod, beaker, water.
Procedure: Transfer 100cm³ of water from a beaker into a test tube. Add 0.5g of common salt at a time, stirring with the glass rod after each addition, and continue until the salt stops dissolving and settles at the bottom.
Observation: after a certain amount has been added, no more salt will dissolve. Conclusion: there is a limit to how much solute a given amount of solvent can dissolve.
Types of Solution
- Dilute: a small amount of solute in a large amount of solvent.
- Concentrated: a large amount of solute in the same amount of solvent.
- Unsaturated: can still dissolve more solute at the same temperature.
- Supersaturated: contains more dissolved solute than it would normally hold at that temperature.
Crystallisation
Crystallisation is the process of cooling a saturated solution so that it forms crystals — solids with a regular shape and size. It’s used to purify a solute. There are four types of crystal: ionic, covalent, molecular and metallic.
