Mixture – IGCSE Chemistry Definition
IGCSE Chemistry definition of mixture: two or more substances not chemically combined. Covers separation methods and comparison with compounds.
Published by IGCSEChemistry.com.my
Chemistry teaching team: K. S. Tan (15+ years teaching IGCSE Chemistry) and Ms Yash (10+ years teaching IGCSE Chemistry) and Ms Kartini (15+ years teaching IGCSE Chemistry).
Mapped to Cambridge IGCSE Chemistry 0620 (2026–2028). Last updated 2026-08-19.
A mixture is two or more substances not chemically bonded together. This definition appears directly on Paper 1 and Paper 2, and the ability to choose the correct separation method for a given mixture is one of the most frequently tested practical skills on Paper 6.
The 0620 definition
A mixture consists of two or more substances (elements or compounds) that are not chemically combined. Each substance in a mixture retains its own chemical properties and can be separated by physical methods.
Key properties of mixtures
| Property | Detail |
|---|---|
| Composition | Variable proportions |
| Properties | Each substance keeps its own properties |
| Separation | Physical methods only |
| Bonding | No chemical bonds between the different substances |
| Melting/boiling point | Melts/boils over a range of temperatures (not a sharp point) |
Separation methods
| Method | Used for | Example |
|---|---|---|
| Filtration | Insoluble solid from a liquid | Sand from water |
| Evaporation | Dissolved solid from a solution | Salt from salt water |
| Simple distillation | Solvent from a solution (collecting the liquid) | Pure water from salt water |
| Fractional distillation | Two or more miscible liquids with different boiling points | Ethanol from water |
| Chromatography | Dissolved substances (e.g. dyes, pigments) | Identifying dyes in food colouring |
| Separating funnel | Two immiscible liquids | Oil from water |
Compound vs mixture summary
| Feature | Compound | Mixture |
|---|---|---|
| Composition | Fixed ratio | Any proportion |
| Properties | Different from components | Same as individual components |
| Separation | Chemical methods only | Physical methods |
| Bonding | Chemical bonds present | No chemical bonds between substances |
| Example | Water (H₂O) | Salt water |
Worked exam question
A student has a mixture of salt and sand. Describe how you would obtain a pure, dry sample of salt from this mixture. (4)
Mark scheme
Add water and stir to dissolve the salt [1]; filter the mixture to remove the sand (sand stays on the filter paper as the residue) [1]; heat/evaporate the filtrate (salt solution) to evaporate the water [1]; until dry salt crystals remain / stop heating before completely dry and allow to crystallise [1]
Common exam mistakes
- Confusing a mixture with a compound. Air is a mixture of gases (N₂, O₂, CO₂, etc.) — they are not bonded together. Water is a compound — hydrogen and oxygen are chemically bonded.
- Choosing the wrong separation technique. Match the method to the type of mixture: filtration for insoluble solids in liquids, distillation for solutions when you want the liquid, chromatography for dissolved coloured substances.
- Saying that substances in a mixture “change their properties”. They do not — each keeps its own properties. This is a defining difference from compounds.
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