Worksheets › Class 9 › Exploring Mixtures and their Separation › Cheat sheet
Class 9 Exploring Mixtures and their Separation: cheat sheet
CBSE Science. Mixtures and pure substances, solutions, suspensions and colloids, concentration, and how to separate the parts of a mixture.
Key ideas
- A pure substance has one kind of particle; a mixture has two or more, in any proportion, and keeps their properties.
- A solution is a uniform mixture with tiny particles that do not settle or scatter light.
- A suspension has large particles that settle; a colloid has middle-sized particles that scatter a beam of light (Tyndall effect).
- Solubility is the most solute that dissolves in 100 g of water at a given temperature; it usually rises with temperature for solids.
- Compounds have fixed proportions and new properties; their parts can be separated only by chemical means.
Remember
| Mass by mass concentration | mass of solute ÷ mass of solution × 100 |
| Solution | solute + solvent |
| Separation methods | evaporation, centrifugation, separating funnel, sublimation, chromatography, distillation, crystallisation |
| Examples | camphor or ammonium chloride: sublimation; ink dyes: chromatography; cream from milk: centrifugation |
Watch out
- Dividing by the mass of the solvent instead of the solution.
- Calling a colloid a solution because it looks clear.
- Choosing evaporation to get pure crystals (crystallisation gives purer ones).
Worked example
Solution P has 20 g of sugar in 125 g of water; solution Q has 50 g of sugar in 175 g of water. (a) Find the concentration of each (mass by mass). (b) Which is more concentrated? (c) If they are mixed, what is the concentration of the mixture?
Working: mixture: (20 + 50) ÷ (145 + 225) × 100
Answer: (a) P: 13.79%, Q: 22.22%. (b) Q. (c) 18.92%
Practise Exploring Mixtures and their Separation
Revise with this page, then practise: every Exploring Mixtures and their Separation sheet in the app is new, with an answer key and working.
Coming soon for Android and iPhone.