NCERT Solutions for Class 9th Science Chapter 5 .1 How Can We Classify Mixtures? — In-text Questions
Book page 735 Updated on2026-09-08
Q1.
Is the mixture of oil and water homogeneous or heterogeneous?
Answer
Heterogeneous. Oil and water are immiscible — they refuse to mix, and however hard you stir they settle back into two separate layers with a visible boundary between them.
Why it happens: A homogeneous mixture must have the same composition in every part. Draw a drop from the top of an oil–water mixture and you get oil; draw one from the bottom and you get water. The composition is not the same everywhere, so the mixture is heterogeneous. At the particle level, water molecules attract one another strongly and oil molecules do not join in, so the two sets of molecules stay apart instead of spreading through each other.
Q2.
Can you think of some other heterogeneous mixtures?
Answer
Yes — any mixture in which you can point to more than one part is heterogeneous.
Solid in liquid: sand in water, chalk powder in water, muddy water, tea leaves in water.
Liquid in liquid: mustard oil and water, kerosene and water.
Solid in solid: iron filings and sulfur, sand and common salt, a handful of mixed dal.
Solid or liquid in gas: smoke (solid particles in air), fog and clouds (water droplets in air), dust in air.
Tip: Alloys such as brass and bronze look like solid–solid mixtures but are homogeneous — the metals were melted together, so they are mixed right down to the level of individual atoms.