Class 9 Science Chapter 5 Exploring Mixtures and their Separation – Revision Notes

Pure substances and mixtures split further into solutions, suspensions, and colloids depending on how they behave, and Chapter 5 explains the techniques, such as crystallisation and distillation, used to pull them apart.

Last Updated: September 23, 2026

Pure Substances vs Mixtures

• Pure substance: fixed composition.
• Mixture: variable proportions of 2+ substances.

Types of Mixtures

• Homogeneous: uniform, e.g. salt water.
• Heterogeneous: visibly distinct parts, e.g. sand + water.

Solution vs Suspension vs Colloid

• Solution: fully dissolved, no settling, no light scattering.
• Suspension: visible particles, settle over time.
• Colloid: intermediate size, doesn’t settle, shows Tyndall effect (scatters light).

Separation Techniques

• Crystallisation — pure solid crystals from solution.
• Distillation — separates liquids by boiling point.
• Paper chromatography — separates by differing solubility/movement.
• Sublimation — separates sublimable solids (camphor, NH4Cl).
• Centrifugation — separates by density using high-speed spin.
• Coagulation — clumps and settles colloidal particles.

Quick visual: a worked diagram from the full Solutions page, for reference.

One-Line Summary

Mixtures range from homogeneous solutions to heterogeneous suspensions, with colloids in between, and specific techniques — crystallisation, distillation, chromatography, sublimation, centrifugation, and coagulation — are chosen based on the properties of the components to be separated.

Frequently Asked Questions

What is the difference between a mixture and a pure substance?
A pure substance has a fixed composition and definite properties, such as a single element or compound, while a mixture contains two or more substances combined in variable proportions without any fixed chemical composition.

What is the difference between homogeneous and heterogeneous mixtures?
A homogeneous mixture has a uniform composition throughout, such as salt dissolved in water, while a heterogeneous mixture has visibly different components or phases, such as sand mixed with water.

Written by Satish

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