medium difficulty7 min

Classifying Mixtures

A mixture is a physical combination of two or more substances in which the components keep their own properties and can usually be separated by physical methods.

In one line: Homo means same; hetero means different.

Practice This Concept

Understand it

Mixtures are classified mainly as homogeneous and heterogeneous. A homogeneous mixture has uniform composition throughout, so its different parts cannot be easily seen. A heterogeneous mixture has non-uniform composition, so different parts may be visible or unevenly distributed.

Example

Salt completely dissolved in water is homogeneous, while sand mixed with iron filings is heterogeneous.

Rule to remember

Rule: uniform composition throughout means homogeneous; non-uniform composition means heterogeneous.

See it worked out

Follow the example line by line, then use the same method on new questions.

Worked example

Classify air, muddy water, and sugar solution.

1Air is homogeneous because gases are uniformly mixed.
2Muddy water is heterogeneous because soil particles are uneven and may settle.
3Sugar solution is homogeneous when sugar dissolves completely.

Method you can reuse

1Observe whether the composition is uniform.
2Check if particles or layers are visible.
3Decide homogeneous or heterogeneous.
4Add one example-based reason.

Visual tip

A simple two-beaker sketch can show clear salt solution as uniform and sand-water mixture with settled particles as non-uniform.

Check yourself

Answer the question in your head before opening the answer.

Try it yourself

Why is salt water called a homogeneous mixture even though it has two substances?

Think first, then show answer

Salt water is called a homogeneous mixture because the dissolved salt is spread uniformly throughout the water, so any small sample has the same composition.

Common wrong answer

Calling milk a true solution.

Why it loses marks: Milk is a colloid; it appears uniform but has dispersed particles.

Don't mix this up

Many students call every clear liquid a pure substance. A clear salt solution is still a mixture because it has salt and water.

Exam tip

When classifying, write both the type and the reason: uniform composition for homogeneous, non-uniform composition for heterogeneous.

Write it in the exam

Each point is worth about one mark. Write point 1 for a 1-mark question and keep adding points as the marks go up.

How CBSE asks it

Questions often ask students to classify common mixtures and justify the answer in one reason-based sentence.

1
Enough for 1 mark
A mixture is a physical combination of two or more substances in which the components keep their own properties and can usually be separated by physical methods.
2
Add for 2 marks
Example: Salt completely dissolved in water is homogeneous, while sand mixed with iron filings is heterogeneous.
3
Add for 3 marks
Mixtures are classified mainly as homogeneous and heterogeneous.

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