NCERT Solutions for Class 8th Science Chapter 8 Nature of Matter: Elements, Compounds, and Mixtures
Updated on 2026-09-19
About this chapter
A mixture is two or more substances mixed together in which each substance keeps its own properties and no chemical reaction takes place. The substances that make it up are its components . A mixture is uniform when its components are evenly spread and cannot be told apart even under a microscope (air, sugar in water, alloys), and non-uniform when they can be seen separately (sprout salad, sand and water). A pure substance contains only one kind of particle and cannot be separated into other kinds of matter by any physical process. Every pure substance is either an element or a compound. Elements cannot be broken down into simpler substances. Each is made of identical atoms ; two or more atoms usually join into a molecule . 118 elements are known — mostly solids, eleven gases, and only mer
- Chapter opener
- .1 What Are Mixtures?
- .1.1 Is air a mixture?
- .1.2 Types of mixtures
- .2 What Are Pure Substances?
- .3 What Are the Types of Pure Substances?
- .3.1 Elements
- .3.2 Compounds
- End-of-chapter questions
- Science • Society • Interdisciplinary Projects
Quick revision
| Term | What it means | How you can tell | Example from the chapter |
|---|---|---|---|
| Mixture | Two or more substances mixed; each keeps its own properties, no chemical reaction | Components can be separated by a physical method; composition can vary | Poha, sprout salad, air, seawater |
| Component | An individual substance that makes up a mixture | It is still itself inside the mixture | Green gram, chickpeas, onion, tomato in a sprout salad |
| Uniform mixture | Components evenly spread; cannot be distinguished even with a microscope | Looks the same throughout | Sugar in water, air, brass, bronze, stainless steel |
| Non-uniform mixture | Components visible to the naked eye or with a magnifying device | You can point to the separate bits | Sprout salad, sand and water, muddy water |
| Alloy | A uniform mixture of metals (and sometimes a little carbon) | Looks like one metal, but is a mixture | Brass (copper + zinc), bronze (copper + tin), stainless steel |
| Pure substance | Matter made of only one kind of particle | Cannot be separated into other kinds of matter by any physical process | Oxygen, iron, water, sodium chloride, sugar |
| Element | A substance that cannot be broken down into simpler substances | Made of identical atoms; it is a building block of matter | Hydrogen, oxygen, gold, silver, sulfur, carbon |
| Atom | The identical particle an element is made of | Different from the particle of every other element | An atom of hydrogen; an atom of oxygen |
| Molecule | A stable particle formed when two or more atoms combine | Two hydrogen atoms give one hydrogen molecule (Fig. 8.10) | Molecule of hydrogen; molecule of oxygen |
| Compound | Different elements combined chemically in a fixed ratio | New properties; elements cannot be separated physically | Water (hydrogen : oxygen = 2 : 1), sodium chloride (1 : 1), iron sulfide, sugar |
| Metals / non-metals / metalloids | The two main classes of elements, and the in-between class | Gold, iron are metals; carbon, sulfur are non-metals; silicon, boron are metalloids | Silicon and boron have properties between the two |
| Mineral | A natural solid of the Earth with a fixed chemical composition | Mostly a compound; a native mineral is a pure element | Quartz, calcite, mica, pyroxene, olivine, talc; gold and sulfur are native minerals |
Exercises
- Chapter opener — Probe and ponder Page 116
- .1 What Are Mixtures? — In-text Questions Page 1178
- .1 What Are Mixtures? — A step further Page 1188
- .1.1 Is air a mixture? — In-text Questions Page 1188
- .1.1 Is air a mixture? — Activity 8.1: Let us experiment Page 1188
- .1.1 Is air a mixture? — In-text Questions Page 1198
- .1.1 Is air a mixture? — Activity 8.2: Let us explore Page 1198
- .1.2 Types of mixtures — In-text Questions Page 1208
- .2 What Are Pure Substances? — A step further Page 1218
- .3 What Are the Types of Pure Substances? — Activity 8.3: Let us experiment (Demonstration activity) Page 1218
- .3.1 Elements — Ever heard of ... Page 1238
- .3.2 Compounds — In-text Questions Page 1248
- .3.2 Compounds — Activity 8.4: Let us experiment Page 1248
- .3.2 Compounds — In-text Questions Page 1258
- .3.2 Compounds — Activity 8.5: Let us experiment (Demonstration activity) Page 1258
- .3.2 Compounds — Some discussion points Page 1288
- .3.2 Compounds — In-text Questions Page 1288
- End-of-chapter questions — Keep the curiosity alive Page 131
- Science • Society • Interdisciplinary Projects — Discover, design, and debate Page 133