NCERT Solutions for Class 8th Science Chapter 9 The Amazing World of Solutes, Solvents, and Solutions
Updated on 2026-09-19
About this chapter
A uniform mixture — one in which the components are spread evenly and cannot be picked out — is a solution . Salt or sugar in water is a solution; chalk powder, sand or sawdust in water is a non-uniform mixture . When a solid dissolves in a liquid, the solid is the solute and the liquid is the solvent . When two liquids mix, the one present in the smaller amount is the solute. A solution that can still dissolve more solute at that temperature is unsaturated ; once the solute stops dissolving and settles at the bottom, the solution is saturated at that temperature. The amount of solute in a fixed quantity of solution is its concentration (dilute or concentrated); the maximum that dissolves in a fixed quantity (100 mL) of solvent is its solubility . Raising the temperature generally increase
- Chapter opener
- .1 What Are Solute, Solvent, and Solution?
- .2 How Much Solute Can a Fixed Amount of Solvent Dissolve?
- Activity 9.1
- .2.1 How does temperature affect the solubility of a solute?
- Our scientific heritage
- .3 Solubility of Gases
- .5 What Is Density?
- .5.1 Determination of density
- Activity 9.5: Let us measure 50 mL of water
Quick revision
| Term | What it means | Example from the chapter | Value / unit |
|---|---|---|---|
| Solution | A uniform mixture whose components cannot be seen separately | Salt and sugar in water (ORS); air; sugar syrup of gulab jamun | — |
| Solute / Solvent | The dissolved substance / the substance that dissolves it; between two liquids, the smaller amount is the solute | Sugar (solute) in water (solvent) in chashni | — |
| Saturated solution | No more solute can dissolve in it at that temperature; extra solute settles at the bottom | Salt added spoon by spoon in Activity 9.1 | — |
| Unsaturated solution | More solute can still be dissolved at that temperature | The same salt solution after one or two spoons | — |
| Concentration | Amount of solute in a fixed quantity of solution — dilute or concentrated | 4 spoons in 50 mL is 4 times as concentrated as 2 spoons in 100 mL | spoons per 100 mL |
| Solubility | Maximum solute that dissolves in a fixed quantity (100 mL) of solvent at a stated temperature | Baking soda: more dissolves at 70 °C than at 50 °C or 20 °C | g per 100 mL |
| Mass | The quantity of matter in an object; measured on a balance | Stone weighed on a digital balance | 16.400 g |
| Weight | The force with which the Earth pulls an object — not the same as mass | Most balances really measure weight but are marked in mass units | newton (N) |
| Volume | The space an object occupies | Notebook 25 cm × 18 cm × 2 cm; stone by displacement | 900 cm³; 5 cm³ |
| Least count of a measuring cylinder | The smallest volume it can read | 100 mL cylinder: 10 mL between marks ÷ 10 divisions | 1 mL |
| Density | Mass present in unit volume, Mass / Volume | Aluminium block 27 g in 10 cm³; stone 16.400 g in 5 cm³ | 2.7 g/cm³; 3.28 g/cm³ |
| Relative density | Density of a substance ÷ density of water at that temperature | Aluminium with respect to water | 2.7 (no unit) |
Exercises
- Chapter opener — Probe and ponder Page 134
- .1 What Are Solute, Solvent, and Solution? — In-text Questions Page 1359
- .2 How Much Solute Can a Fixed Amount of Solvent Dissolve? — Activity 9.1: Let us investigate Page 1369
- Activity 9.1 — Some discussion points Page 136
- .2 How Much Solute Can a Fixed Amount of Solvent Dissolve? — In-text Questions Page 1369
- .2 How Much Solute Can a Fixed Amount of Solvent Dissolve? — In-text Questions Page 1379
- .2.1 How does temperature affect the solubility of a solute? — Activity 9.2: Let us experiment (Demonstration activity) Page 1379
- Our scientific heritage — Be a scientist Page 138
- .3 Solubility of Gases — In-text Questions Page 1399
- .4 Why Do Objects Float or Sink in Water? • 9.5 What Is Density? — In-text Questions Page 1409
- .5 What Is Density? — Think like a scientist Page 1419
- .5.1 Determination of density — In-text Questions Page 1439
- .5.1 Determination of density — Activity 9.4: Let us observe and calculate Page 1439
- .5.1 Determination of density — In-text Questions Page 1449
- Activity 9.5: Let us measure 50 mL of water — In-text Questions Page 145
- Determining volume of objects with irregular shapes — Activity 9.7: Let us measure Page 146
- Let us dig deeper! — In-text Questions Page 147
- .5.3 Effect of pressure on density — Ever heard of ... Page 1489
- .5.3 Effect of pressure on density — Think like a scientist Page 1489
- End-of-chapter question set (pages 149–151) — Keep the curiosity alive Page 149
- Science • Society • Interdisciplinary Projects — Discover, design, and debate Page 151