In this chapter, we learn about metals and non-metals and their important properties. We study malleability, ductility, sonority, conduction of heat and conduction of electricity. We also learn how metals react with air and water, how iron rusts, how corrosion takes place, and how non-metals behave differently.

The chapter also explains the importance of metals and non-metals in our everyday life.

Materials can have different properties. Metals such as iron, copper and aluminium have some common properties that make them useful for many purposes.

Iron can be heated and beaten with a hammer to change its shape. Copper, aluminium and iron can become flat when hammered.

Gold and silver are among the most malleable metals.

Aluminium foil and silver foil are examples of thin metal sheets made using this property.

Wood neither becomes a thin sheet nor breaks into pieces in the same way. Therefore, wood is neither malleable nor brittle.

The Harappans knew how to use metals such as copper and gold. Iron became important later. Because iron is strong, iron agricultural tools such as ploughs were much more useful and stronger than many earlier tools.

Copper and aluminium are commonly used to make electrical wires. Metal wires are also used in ornaments and stringed musical instruments such as the veena, sitar, violin and guitar.

Gold is highly ductile. One gram of gold can be drawn into a very long wire.

Metal spoons and coins produce a ringing sound when dropped or struck. Coal and wood generally produce dull sounds.

School bells and ghungroos produce ringing sounds because of the sonority of metals.

Metals are generally good conductors of heat. Wood is a poor conductor of heat.

This is why cooking vessels are mostly made of metals. Their handles may be made of wood or other materials that conduct heat poorly.

Metals such as aluminium, iron and copper allow electricity to pass through them easily. They are good conductors of electricity.

Materials such as sulfur, coal, wood, stone, rubber and nylon do not allow electricity to pass through easily. They are poor conductors of electricity.

Iron objects often develop a brown deposit when they are exposed to moist air. This brown deposit is called rust.

• Painting
• Oiling
• Greasing
• Applying a protective zinc coating on iron, called galvanisation

The Iron Pillar of Delhi was made more than 1600 years ago. It is famous for its remarkable resistance to corrosion.

The pillar shows the advanced skills of ancient Indian metalworkers.

Magnesium ribbon burns with a dazzling white flame in air and forms a white powder called magnesium oxide.

Magnesium oxide forms a basic solution when mixed with water. It changes red litmus paper to blue.

Sodium reacts very vigorously with oxygen and water and produces a lot of heat. Therefore, sodium is stored in kerosene to prevent contact with air and moisture.

Sulfur is a non-metal. When sulfur burns in air, sulfur dioxide gas is formed. When sulfur dioxide dissolves in water, sulfurous acid is formed. Therefore, the resulting solution is acidic.

Metals and non-metals are sub-categories of elements. There are presently 118 known elements. They are the basic building blocks of all matter.

Non-metals are very important in everyday life.

• Oxygen: Needed for respiration and survival.
• Carbon: A building block of life and present in proteins, fats and carbohydrates.
• Nitrogen: Used in fertilisers and important for plant growth.
• Chlorine: Used in water purification.
• Iodine: Used as an antiseptic on wounds.

Metals and alloys are important for utensils, tools, modern technology and industries. Special metals are also used in areas such as atomic energy and aerospace.

Recycling metals such as iron and aluminium helps minimise waste and supports sustainability.

• Metals and non-metals are differentiated based on their properties.
• Generally, metals are lustrous, whereas most non-metals are non-lustrous.
• Metals are generally malleable and ductile, while non-metals do not have these properties.
• Metals are good conductors of heat and electricity, but non-metals are generally poor conductors.
• Metals react with oxygen to produce metal oxides which are basic in nature.
• Non-metals react with oxygen to produce oxides which are acidic in nature.
• Generally, non-metals do not react with water.
• Metal objects get damaged when exposed to moist air, and the process is known as corrosion.
• Metals and non-metals have wide applications in everyday life.

Metallic lustre: The shiny appearance shown by metals.

Malleability: Ability to be beaten into thin sheets.

Ductility: Ability to be drawn into wires.

Sonority: Ability to produce a ringing sound.

Conduction: Transfer of heat from one point to another.

Good conductor: A material that allows heat or electricity to pass through easily.

Poor conductor: A material that does not allow heat or electricity to pass through easily.

Rust: Brown deposit formed on iron in the presence of air and water.

Rusting: Formation of rust on iron.

Corrosion: Gradual deterioration of a metal surface due to air, water or other substances.

Galvanisation: Protecting iron by applying a coating of zinc.

Element: A substance that cannot be broken down into simpler substances.

• Metals are generally shiny, hard, malleable and ductile.
• Metals generally produce a ringing sound.
• Metals are generally good conductors of heat and electricity.
• Malleability means ability to form thin sheets.
• Ductility means ability to form wires.
• Sonority means production of a ringing sound.
• Iron rusts when both air and water are present.
• Rust is a brown deposit on iron.
• Painting, oiling, greasing and galvanisation can help prevent rusting.
• Magnesium oxide is basic.
• Sulfur dioxide forms an acidic solution with water.
• Non-metals are also essential in everyday life.
• Oxygen is needed for respiration.
• Nitrogen is important for plant growth and fertilisers.
• Chlorine is used in water purification.
• Iodine can be used as an antiseptic.