Class 8 Science (Curiosity) Chapter 9: The Amazing World of Solutes, Solvents and Solutions

October 22, 2026

Class 8 Science (Curiosity) Chapter 9: The Amazing World of Solutes, Solvents and Solutions – real page from the NCERT Guide book

New NCERT Curiosity · Class 8 Science · Term II · Chapter 9: The Amazing World of Solutes, Solvents and Solutions

This chapter explains solutions as uniform mixtures of a solute dissolved in a solvent. It covers saturation, concentration and solubility of solids and gases, and then introduces density — how to measure mass and volume and why some things float while others sink.

From the Class 8 Science Short Notes, made as per the new NCERT book Curiosity · Pages 53–59 of the book.

Key points

A solution is a uniform mixture; the solute dissolves in the solvent.
When two liquids mix, the one in the smaller amount is the solute and the larger one is the solvent.
A fixed amount of water can dissolve only a limited amount of salt.
An unsaturated solution can dissolve more solute; a saturated solution cannot at that temperature.
Dilute and concentrated are relative terms that describe how much solute is present.
For most solids, solubility increases with temperature; for gases, it decreases.
The small amount of dissolved oxygen in water keeps aquatic life alive.
Density is mass per unit volume; it does not depend on shape or size but on temperature and pressure.
Oil (0.91 g/mL) is less dense than water, so it floats.
The volume of an irregular solid is found by the displacement method in a measuring cylinder.
Heating lowers density; that is why hot air rises. Water is densest at 4 °C, so ice floats.

Formulas

Density	Density = Mass ÷ Volume SI unit kg/m³; also g/mL and g/cm³.
Relative density	Relative density = density of substance ÷ density of water It has no unit.
Unit conversion	1 kg/m³ = 1 g/L
Volume units	1 L = 1 dm³; 1 mL = 1 cm³ = 1 cc
Volume of a cuboid	Volume = l × w × h Notebook: 25 cm × 18 cm × 2 cm = 900 cm³.
Volume by displacement	Volume of stone = B − A 55 mL − 50 mL = 5 cm³.
Least count of measuring cylinder	10 mL ÷ 10 divisions = 1 mL For a 100 mL cylinder.
Density of aluminium (example)	27 g ÷ 10 cm³ = 2.7 g/cm³

Key terms

Solution: A uniform mixture, e.g. salt or sugar in water.
Solute: The substance that dissolves (in a solid + liquid solution, the solid).
Solvent: The liquid in which the solute dissolves.
Saturated solution: A solution in which no more solute can dissolve at that temperature.
Concentration: The amount of solute in a fixed quantity of solution or solvent.
Solubility: The maximum amount of solute that can dissolve in a fixed quantity of solvent at a particular temperature.
Density: The mass present in a unit volume of a substance.
Meniscus: The curved surface of a liquid in a measuring cylinder.

Diagrams to learn

Unsaturated and saturated solutions (Fig 9.1)
Volume of a stone by displacement (Fig 9.2)
Table of effect of temperature on solubility of solids and gases
Table of smallest readings of measuring cylinders

Remember for the exam

In sugar syrup there is a lot of sugar in a little water, yet water is still the solvent.
It is not simply that 'light things float and heavy things sink' — density explains a lot, but it is not the only factor.
Mass and weight are not the same; most balances measure weight but show it in g or kg.
Read the bottom of the meniscus for a colourless liquid and keep your eye level with it.

A real page from the book

Class 8 Science Short Notes, The Amazing World of Solutes, Solvents and Solutions: page 58

Get the full chapter in the book

This page is a summary. The Class 8 Science Short Notes has the complete chapter in colour, with every diagram and worked example.

See the Science book Class 8 full set (3 books)

Frequently asked questions

What is the difference between a saturated and an unsaturated solution?

An unsaturated solution can still dissolve more solute at that temperature. A saturated solution cannot dissolve any more, and the extra solute settles at the bottom.