Solutions
Section: 12. Experimental Techniques & Chemical Analysis | Syllabus: Cambridge IGCSE Chemistry (0620)
Solute, Solvent and Solution
- Solute: a substance that is dissolved in a solvent
- Solvent: a substance that dissolves a solute
- Solution: a mixture of one or more solutes dissolved in a solvent
For example, in salt solution: sodium chloride is the solute, water is the solvent, and the mixture formed is the solution.
Worked Example
- Question: sugar is stirred into a cup of water until it disappears. Identify the solute, the solvent and the solution.
- Answer: solute = sugar (the substance dissolved); solvent = water (the substance doing the dissolving); solution = sugar solution (the resulting mixture).
Saturated Solutions
A saturated solution is a solution containing the maximum concentration of a solute dissolved in the solvent at a specified temperature.
- In a saturated solution, no more solute will dissolve at that temperature - any extra solute added remains undissolved
- Because solubility usually increases with temperature, a solution that is saturated when hot may no longer be saturated once cooled, or excess solute may crystallise back out as the solution cools
Residue and Filtrate
These terms describe the two products of filtration (and similar separation processes):
- Residue: a substance that remains after evaporation, distillation, filtration, or a similar process
- Filtrate: a liquid or solution that has passed through a filter
For example, when a mixture of sand and water is filtered: the sand left on the filter paper is the residue, and the water that passes through is the filtrate.
Common Mistakes
- ❌ Mixing up "residue" and "filtrate"
- ✓ the residue stays behind (on the filter paper, or after evaporation); the filtrate is the liquid that gets through - "filtrate" and "filters through" share the same root to help you remember which is which
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