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Suspensions and Colloids

A suspension is a heterogeneous mixture with large particles that may settle, while a colloid has smaller dispersed particles that do not settle easily and appear fairly uniform.

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Student-friendly explanation

True solutions, colloids, and suspensions differ mainly in particle size and stability. Solution particles are very small and do not scatter light clearly. Colloidal particles are larger than solution particles and can scatter light. Suspension particles are large enough to be seen or settle on standing.

How to write this in exams

  1. 1

    Start with the exact idea

    A suspension is a heterogeneous mixture with large particles that may settle, while a colloid has smaller dispersed particles that do not settle easily and appear fairly uniform.

  2. 2

    Then show how to use it

    Check whether particles settle. Check whether particles can be filtered. Check whether light is scattered. Use these observations to classify the mixture.

  3. 3

    Add one concrete example

    Muddy water is a suspension, milk is a colloid, and salt water is a true solution.

  4. 4

    Avoid this incomplete answer

    Calling milk a suspension is wrong because its particles do not settle quickly like large suspension particles.

Definition

A suspension is a heterogeneous mixture with large particles that may settle, while a colloid has smaller dispersed particles that do not settle easily and appear fairly uniform.

Example

Muddy water is a suspension, milk is a colloid, and salt water is a true solution.

Rule to remember

Comparison rule: true solution has smallest particles, colloid has intermediate particles, suspension has largest particles.

Memory hook

Solution stays clear, colloid scatters, suspension settles.

Examples and method

Worked example

Classify salt water, milk, and chalk powder in water. Salt water is a true solution, milk is a colloid, and chalk powder in water is a suspension.

Method to apply

Check whether particles settle. Check whether particles can be filtered. Check whether light is scattered. Use these observations to classify the mixture.

Diagram support

A three-column comparison chart can show particle size, settling, filtration, and Tyndall effect.

How CBSE asks it

Students are often asked to compare solution, colloid, and suspension in tabular form.

Avoid common mistakes

Common confusion

Students often call colloids true solutions because they look uniform to the naked eye.

Common wrong answer

Calling milk a suspension is wrong because its particles do not settle quickly like large suspension particles.

Exam tip

Use particle size, settling behaviour, filtration, and light scattering for comparison questions.

Quick check

Why is muddy water called a suspension rather than a true solution?

Muddy water is called a suspension because soil particles are not dissolved uniformly, are large enough to settle, and can often be separated by filtration.

Answer writing and exam use

1-mark answer

A suspension is a heterogeneous mixture with large particles that may settle, while a colloid has smaller dispersed particles that do not settle easily and appear fairly uniform.

2-mark answer

A suspension is a heterogeneous mixture with large particles that may settle, while a colloid has smaller dispersed particles that do not settle easily and appear fairly uniform. Comparison rule: true solution has smallest particles, colloid has intermediate particles, suspension has largest particles. Muddy water is a suspension, milk is a colloid, and salt water is a true solution.

3-mark answer

True solutions, colloids, and suspensions differ mainly in particle size and stability. Solution particles are very small and do not scatter light clearly. Colloidal particles are larger than solution particles and can scatter light. Suspension particles are large enough to be seen or settle on standing. Comparison rule: true solution has smallest particles, colloid has intermediate particles, suspension has largest particles. Classify salt water, milk, and chalk powder in water. Salt water is a true solution, milk is a colloid, and chalk powder in water is a suspension. Students are often asked to compare solution, colloid, and suspension in tabular form. Calling milk a suspension is wrong because its particles do not settle quickly like large suspension particles.
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