NCERT Solutions for Class 7th Science Chapter 4 The World of Metals and Non-metals
Updated on 2026-09-19
About this chapter
Metals are generally lustrous (they show metallic lustre), hard , malleable (can be beaten into thin sheets), ductile (can be drawn into wires) and sonorous (give a ringing sound). Copper, aluminium, iron, gold and silver are metals. There are exceptions to every rule — sodium and potassium are so soft they can be cut with a knife , and mercury is a liquid at room temperature. Metals are good conductors of heat and electricity . That is why cooking vessels are metal while their handles are wood, and why an electrician's screwdriver has a plastic grip and rubber gloves. Non-metals such as coal (carbon), sulfur and phosphorus are dull, soft, brittle, non-ductile, non-sonorous and poor conductors of heat and electricity. Metal oxides are basic — burning magnesium gives magnesium oxide, whose
- Yashwant and Anandi visit the ironsmith
- Malleability
- The impact of iron on the progress of civilisation of India
- Ductility and 4.1.3 Sonority
- Sonority
- Conduction of heat
- Conduction of electricity
- Effect of Air and Water on Metals: Iron
- Corrosion
- Effect of Air and Water on Other Metals
Quick revision
| Term | What it means | Where it comes in the chapter | Everyday example |
|---|---|---|---|
| Metallic lustre | The shine shown by the surface of a metal | Section 4.1.1, page 43 | A freshly cut piece of aluminium, a polished steel plate |
| Malleability | The property by which a material can be beaten into thin sheets | Section 4.1.1, page 43 | Silver foil (vark) on sweets, aluminium foil for wrapping rotis |
| Brittle | Breaks into pieces on hammering instead of flattening | Page 44 | A lump of coal, a piece of sulfur, a clay kulhad |
| Ductility | The property by which a material can be drawn into wires | Section 4.1.2, page 44 | Copper wire in a fan, the strings of a sitar or veena |
| Sonority | The property of metals of producing a ringing sound | Section 4.1.3, page 46 | The school bell, ghungroos, a steel plate falling down |
| Conduction | Transfer of heat from one point of a material to another | Section 4.1.4, page 47 | A steel spoon left in hot tea becomes hot at the top |
| Good conductor of electricity | A material that lets electricity pass through it easily | Section 4.1.5, page 48 | Copper wiring in the house, an iron nail in a tester |
| Poor conductor of electricity | A material that does not let electricity pass through it | Section 4.1.5, page 48 | Rubber gloves, the plastic handle of a screwdriver |
| Rust | The brown deposit formed on iron in the presence of both air and water | Section 4.2, page 50 | Brown flakes on an old gate left in the rain |
| Corrosion | Gradual deterioration of a metal surface by air, water or other substances | Page 50 | Green coating on a copper vessel, black coating on silver |
| Galvanisation | Coating iron with a protective layer of zinc metal | Page 50 | Galvanised iron buckets and roofing sheets |
| Element | A substance that cannot be broken down into simpler substances; 118 are known | Page 53 | Oxygen, carbon, iron, gold — but not plastic or glass |
Exercises
- Yashwant and Anandi visit the ironsmith — In-text Questions Page 41 & 42
- Activity 4.1: Let us explore — Malleability Page 42
- In-text Questions — Malleability Page 43
- The impact of iron on the progress of civilisation of India — Holistic Lens Page 44
- In-text Questions — Ductility and 4.1.3 Sonority Page 44 & 45
- Activity 4.2: Let us investigate — Sonority Page 45
- In-text Questions — Conduction of heat Page 46
- Activity 4.3: Let us investigate — Conduction of heat Page 46 & 47
- In-text Questions — Conduction of electricity Page 47
- Activity 4.4: Let us design and create — Conduction of electricity Page 47 & 48
- In-text Questions — Effect of Air and Water on Metals: Iron Page 48
- Activity 4.5: Let us experiment — Effect of Air and Water on Metals: Iron Page 49 & 50
- In-text Questions — Corrosion Page 50
- Activity 4.6: Let us investigate (demonstration activity) — Effect of Air and Water on Other Metals Page 51
- In-text Questions — Sodium Page 52
- Activity 4.7: Let us experiment (demonstration activity) — Substances that Behave Differently from Metals in Air and Water Page 52 & 53
- Activity 4.8: Let us explore — Substances that Behave Differently from Metals in Air and Water Page 53
- In-text Questions — Are Non-metals Essential in Everyday Life? Page 54
- End-of-chapter exercise — Let Us Enhance Our Learning Page 55 & 56
- Projects and further exploration — Exploratory Projects Page 56