📘 Chapter Overview
Metals and non-metals are important groups of substances that surround us. From the iron used in buildings to the copper used in electrical wires, metals are an essential part of modern life.
Non-metals are equally important. Oxygen is necessary for respiration, carbon is present in many living materials, and sulphur and other non-metals have several useful applications.
In this chapter, we explore the characteristic properties of metals and non-metals and understand how these substances are useful in everyday life.
📑 Table of Contents
1. What Are Metals?
Metals are a group of elements that generally possess properties such as lustre, hardness, malleability, ductility and good electrical and thermal conductivity.
🔩 Examples of Metals
Iron
Used in buildings, bridges, tools and machines.
Copper
Commonly used for electrical wires.
Aluminium
Used in utensils, aircraft and packaging.
Gold
Used mainly for jewellery and certain specialised applications.
2. What Are Non-metals?
Non-metals are elements that generally do not show the typical properties of metals. Many non-metals are poor conductors of heat and electricity.
🌱 Examples of Non-metals
- Oxygen
- Nitrogen
- Carbon
- Sulphur
- Phosphorus
- Chlorine
3. Physical Properties of Metals
✨ Lustrous
Many metals have a shiny surface when freshly cut or polished. This property is called lustre.
🔨 Hard
Many metals are hard and strong. However, the hardness of metals varies from one metal to another.
📏 Malleable
Metals can generally be beaten or hammered into thin sheets. This property is called malleability.
🧵 Ductile
Metals can generally be drawn into thin wires. This property is called ductility.
🔔 Sonorous
Many metals produce a ringing sound when struck. Such substances are described as sonorous.
4. Physical Properties of Non-metals
Non-metals generally show properties opposite to many common properties of metals.
- Many non-metals are dull in appearance.
- Solid non-metals are generally brittle.
- They are generally not malleable.
- They are generally not ductile.
- Most non-metals are poor conductors of heat and electricity.
5. Metals vs Non-metals
| Property | Metals | Non-metals |
|---|---|---|
| Appearance | Generally lustrous | Generally dull |
| Malleability | Generally malleable | Generally not malleable |
| Ductility | Generally ductile | Generally not ductile |
| Electrical conductivity | Generally good conductors | Generally poor conductors |
| Sound | Many are sonorous | Generally not sonorous |
| Examples | Iron, copper, aluminium | Oxygen, sulphur, carbon |
6. Malleability and Ductility
🔨 Malleability
The ability of a metal to be beaten into thin sheets is called malleability.
Aluminium sheets are commonly used for packaging because aluminium is malleable.
🧵 Ductility
The ability of a metal to be drawn into thin wires is called ductility.
Copper is widely used for making electrical wires because it is ductile as well as a good conductor of electricity.
Malleability → Make sheets
Ductility → Draw wires
7. Electrical and Thermal Conductivity
Metals generally allow heat and electric current to pass through them easily. This property is called conductivity.
⚡ Electrical Conductivity
Copper and aluminium are commonly used in electrical applications because they conduct electricity well.
🔥 Thermal Conductivity
Many metals also conduct heat efficiently. This is why metals are commonly used for cooking utensils and heat-transfer applications.
8. Chemical Behaviour of Metals and Non-metals
Metals and non-metals can undergo chemical reactions and form new substances.
🔥 Reaction with Oxygen
Many metals react with oxygen to form metal oxides.
Non-metals can also react with oxygen to form non-metal oxides.
💧 Reaction with Water
Some metals react with water, although the reactivity differs greatly from one metal to another.
🧪 Reaction with Acids
Some metals react with acids and may release hydrogen gas. However, not all metals react with acids in the same way.
9. Uses of Metals and Non-metals
🔩 Uses of Metals
- Iron: buildings, bridges, tools and machines.
- Copper: electrical wires and equipment.
- Aluminium: utensils, packaging and aircraft.
- Gold: jewellery and specialised applications.
🌍 Uses of Non-metals
- Oxygen: respiration and medical applications.
- Nitrogen: important for living organisms and agricultural processes.
- Carbon: present in fuels and many compounds.
- Chlorine: used in water treatment and several industrial processes.
- Sulphur: used in several industrial products.
10. Metals and Non-metals in Daily Life
We encounter metals and non-metals throughout our daily lives.
🏠 At Home
Metals are used in utensils, appliances, wires, tools and furniture.
🚗 Transportation
Metals are used in vehicles because many of them are strong and durable.
⚡ Electricity
Copper and aluminium are widely used as conducting materials.
🌱 Agriculture
Several non-metal elements and their compounds are important for plant growth and agricultural activities.
⚡ Quick Revision
📝 Important Questions
Metals are elements that generally have properties such as lustre, malleability, ductility and good electrical and thermal conductivity.
Non-metals are elements that generally do not show the typical physical properties of metals.
Malleability is the ability of a material, especially a metal, to be beaten into thin sheets.
Ductility is the ability of a material to be drawn into thin wires.
Iron, copper and aluminium are examples of metals.
Oxygen, sulphur and carbon are examples of non-metals.
Copper is a good conductor of electricity and is also ductile, allowing it to be drawn into wires.
Many metals conduct heat efficiently and can withstand relatively high temperatures, making them useful for utensils.
Lustre is the shiny appearance shown by many metals.
A sonorous material produces a ringing sound when struck. Many metals show this property.
Most non-metals are poor conductors, but graphite, a form of carbon, is an important exception.
Metals are strong, useful and have properties such as conductivity, malleability and ductility, making them suitable for many applications.
🎯 Exam Tips
- Learn the definitions of metals, non-metals, malleability and ductility.
- Remember at least three examples each of metals and non-metals.
- Learn the differences between metals and non-metals.
- Remember the common uses of iron, copper, aluminium and oxygen.
- Remember the important exception: graphite is a non-metal that conducts electricity.
- Do not treat general properties as absolute rules because science has exceptions.
❓ Frequently Asked Questions
What is Chapter 4 of Class 7 Science?
Chapter 4 is titled “The World of Metals and Non-metals”.
What are the main properties of metals?
Metals generally show lustre, malleability, ductility, sonority and good electrical and thermal conductivity.
What are the main properties of non-metals?
Non-metals generally lack the typical properties of metals. Many are brittle and poor conductors of heat and electricity.
What is malleability?
Malleability is the ability of a material to be beaten into thin sheets.
What is ductility?
Ductility is the ability of a material to be drawn into thin wires.
Is graphite a metal?
No. Graphite is a form of carbon and is a non-metal. It is an important exception because it conducts electricity.
Why is aluminium useful?
Aluminium is lightweight, useful for making sheets and has several applications including utensils, packaging and transportation.