# The World of Metals and Non-Metals

## Overview
This chapter introduces students to the properties and differences between metals and non-metals. Through everyday examples, activities, and investigations, students explore physical properties like malleability, ductility, conductivity, and sonority, as well as chemical reactions of elements with air and water. The chapter encourages observation, classification, and practical learning, supported by real-life applications.

## Key Topics Covered

### 1. Introduction: The Craft of Metalwork
- Yashwant and Anandi visit a local ironsmith to learn about metal crafting.
- Items made: tawas, buckets, tongs, spades, axes, trowels, rakes.
- Metals used: primarily iron; coal used for heating; wooden handles added.

### 2. Properties of Materials

#### 2.1 Malleability
- **Definition**: Property that allows metals to be beaten into thin sheets.
- **Examples**: Copper, iron, and aluminium flatten on hammering. Coal and sulfur break; wood neither flattens nor breaks.
- **Key Observations**:
- Metals: Lustrous, hard, and malleable.
- Non-metals (coal, sulfur): Brittle or soft, non-lustrous.
- **Real-life Uses**: Silver and aluminium foil, utensils, gold jewellery.

#### 2.2 Ductility
- **Definition**: Ability to be drawn into wires.
- **Examples**: Copper, aluminium (used in electrical wiring); gold (high ductility).
- **Uses**: Musical instruments, jewellery, cables.
- **Non-metals**: Not ductile (e.g., coal, sulfur).

#### 2.3 Sonority
- **Definition**: Ability to produce a ringing sound when struck.
- **Metals**: Sonorous (spoons, bells, coins).
- **Non-metals**: Dull sound (wood, coal).

#### 2.4 Conduction of Heat
- **Activity**: Metal vs. wooden spoon in hot water.
- **Observation**: Metal spoon gets hotter due to better heat conduction.
- **Conclusion**: Metals are good conductors of heat. Wood is a poor conductor.
- **Application**: Cooking vessels made of metal; handles made of wood/plastic.

#### 2.5 Conduction of Electricity
- **Activity**: Materials tested in a circuit to light a bulb.
- **Good Conductors (bulb glows)**: Aluminium, copper, iron.
- **Poor Conductors**: Sulfur, coal, dry wood, stone, rubber, nylon.
- **Real-life Safety**: Rubber gloves, plastic handles insulate electricians from shock.


### 3. Effect of Air and Water on Metals

#### 3.1 Rusting of Iron

* **Experiment**: Iron nails in three bottles – dry air, water only, and moist air.
* **Observation**:

* No rust in dry air or water alone.
* Rust forms in presence of both air and water.
* **Conclusion**: Moist air causes rusting.
* **Term**: Rust is the brown deposit formed on iron.
* **Prevention**: Painting, oiling, greasing, galvanisation (coating with zinc).
* **Related Term**: Corrosion – gradual surface damage of metals by air/water.

#### 3.2 Historical Example: Iron Pillar of Delhi

* Over 1600 years old, made in Chandragupta II’s time, barely rusted – shows India’s ancient metallurgy expertise.

### 4. Reaction of Metals with Air and Water

#### 4.1 Magnesium

* Burns with white flame forming white ash – magnesium oxide.
* When dissolved in water, turns red litmus blue → Basic nature.

#### 4.2 Sodium

* Reacts vigorously with air and water.
* Stored in kerosene to prevent reaction.
* Its oxide is also basic.

### 5. Reaction of Non-metals with Air and Water

#### 5.1 Sulfur

* Burns in air forming sulfur dioxide gas.
* Dissolves in water forming sulfurous acid – turns blue litmus red → Acidic.
* No reaction when sulfur is mixed with water alone.

#### 5.2 Other Non-metals

* Phosphorus catches fire in air – stored in water.
* Non-metals are soft, dull, brittle, non-sonorous, and poor conductors.
* Oxides of non-metals are acidic.

#### 5.3 What Are Elements?

* Metals and non-metals are elements – substances that can’t be broken down further.
* 118 known elements; basic building blocks of all matter.

### 6. Uses of Non-metals in Everyday Life

* **Oxygen**: Non-metal essential for respiration.
* **Carbon**: Basis of all living things; part of food (proteins, carbs, fats).
* **Nitrogen**: Used in fertilisers; essential for plant growth.
* **Chlorine**: Used to purify water.
* **Iodine**: Antiseptic applied on wounds.

### 7. Summary Points

* Metals are lustrous, hard, malleable, ductile, sonorous, and good conductors.
* Non-metals are dull, brittle, non-sonorous, and poor conductors.
* Metal oxides are basic; non-metal oxides are acidic.
* Rusting of iron occurs in moist air; prevented by coatings.
* Elements are basic units of matter—metals and non-metals are types of elements.

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## New Terms and Definitions (Simple English)

| Term | Definition |
| ------------- | -------------------------------------------------------------------------------- |
| Malleability | Ability of a material to be beaten into thin sheets. |
| Ductility | Ability of a material to be drawn into wires. |
| Sonority | Ability of a material to make a ringing sound when struck. |
| Conductor | A material that allows heat or electricity to pass through easily. |
| Corrosion | Slow damage of a metal’s surface due to air, water, or other substances. |
| Rust | Brown deposit that forms on iron when it reacts with air and water. |
| Galvanisation | Coating iron with zinc to protect it from rusting. |
| Non-metal | An element that is usually soft, dull, and a poor conductor of heat/electricity. |
| Acidic | A substance that turns blue litmus red. |
| Basic | A substance that turns red litmus blue. |

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## Practice Questions

### Easy (3)

1. **Name one metal used to make wires.**
**Answer**: Copper.
**Explanation**: Copper is ductile and conducts electricity well.

2. **What is rusting?**
**Answer**: Formation of a brown substance on iron when exposed to air and water.
**Explanation**: Rusting happens due to moisture and air.

3. **Which metal is used to make cooking utensils and is very malleable?**
**Answer**: Aluminium.
**Explanation**: Aluminium is cheap, light, and easy to shape.

### Medium (2)

4. **Why are handles of cooking pots made of wood or plastic?**
**Answer**: Because they are poor conductors of heat.
**Explanation**: Wood/plastic protect hands from heat during cooking.

5. **What happens when sulfur is burnt in air?**
**Answer**: It forms sulfur dioxide gas which becomes acidic in water.
**Explanation**: Sulfur dioxide dissolves in water to make sulfurous acid.

### Difficult (3)

6. **Why is sodium stored in kerosene?**
**Answer**: To prevent it from reacting with moisture in air.
**Explanation**: Sodium is very reactive and can catch fire.

7. **How can we prove that metals conduct electricity but non-metals don’t?**
**Answer**: By using a tester circuit.
**Explanation**: Metals make the bulb glow; non-metals don’t.

8. **Explain how corrosion affects the economy.**
**Answer**: Corroded metal structures need frequent repair or replacement.
**Explanation**: This increases maintenance costs for bridges, buildings, etc.

### Very Difficult (2)

9. **Can sulfur be used to coat iron to prevent rusting? Why or why not?**
**Answer**: No, because sulfur does not stick and does not form a protective layer.
**Explanation**: It doesn’t prevent air and water from reaching iron.

10. **Compare the chemical reactions of magnesium and sulfur with oxygen.**
**Answer**: Magnesium forms basic magnesium oxide; sulfur forms acidic sulfur dioxide.
**Explanation**: Metal oxides are basic; non-metal oxides are acidic.

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