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NCERT Solutions Curiosity Chapter 9 .1 What Are Solute, Solvent, and Solution? — In-text Questions

Book page 1359 Updated on2026-09-05

Q1.
Can you predict whether this mixture is uniform or not (Fig. 9.1)?
Answer

It is a uniform mixture. The sugar and salt have dissolved completely in the water, so the liquid is clear and you cannot see the sugar or the salt separately anywhere in the glass.

Why it happens: Water particles pull the sugar and salt particles off their crystals and spread them evenly through the whole liquid. Every drop of the mixture therefore has the same composition — which is why every sip of homemade ORS tastes the same and never salty in one sip and sweet in the next. A uniform mixture like this is called a solution.
Q2.
What happens when chalk powder is mixed with water—does it form a uniform mixture?
Answer

No. Chalk powder does not dissolve. It stays as tiny solid grains that make the water look milky, and if the glass is left standing, the grains slowly settle at the bottom. This is a non-uniform mixture, like sand in water or sawdust in water (Fig. 9.2).

Why it happens: Water particles cannot pull the chalk particles apart from one another — the attraction inside the chalk is much stronger than anything water can offer. So the chalk stays in clumps of many particles, large enough to see and heavy enough to settle. In a solution the solute is broken down to single particles that are far too small to see or to settle.
Check it yourself: Hold the glass up to the light. A solution of sugar in water is clear right through; chalk in water is cloudy. That difference in appearance is the easiest test for uniform against non-uniform.
Q3.
We know air is a mixture. Would a mixture of gases also be considered a solution?
Answer

Yes. Air is a uniform mixture of nitrogen, oxygen, carbon dioxide, water vapour and other gases, and a uniform mixture is a solution. The gases are spread evenly, no component can be seen or picked out separately, and a sample of air taken from anywhere in this room has the same composition.

Following the chapter's own rule for two substances in the same state — the one present in the larger amount is the solvent — nitrogen (about four-fifths of air) is the solvent and oxygen and the rest are the solutes.

Why it happens: Gas particles are very far apart and move about at high speed in every direction. Different gases mixed in one container therefore intermingle completely on their own and stay mixed; they never settle into layers the way sand settles in water.
Tip: A solution does not have to be a liquid. Air is a gas–gas solution, sea water is a solid–liquid solution, and an alloy such as brass is a solid–solid solution.
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