PW Class 7 Science Notes Chapter 4: The World of Metals and Non-Metals

Metals and non-metals are found in many objects and materials we use every day, but their properties and behaviour are quite different. Understanding why metals are shiny and good conductors, why some metals rust, and why non-metals generally have different characteristics can make the chapter difficult to revise. Remembering their uses and reactions with air and water also requires attention to important details.

PW Class 7 Science Chapter 4 Notes simplify these concepts by covering the properties, uses, corrosion, rusting, and reactions of metals and non-metals. You can use these notes to revise key definitions, examples, comparisons, and applications before solving textbook questions and preparing for school assessments.

What Is an Element?

An element is a pure substance made up of only one kind of atom.

Examples of elements:

• Iron

• Oxygen

• Carbon

• Copper

• Neon

Elements are mainly classified into:

• Metals

• Non-metals

• Metalloids (introduced in higher classes)

What Are the Properties of Metals?

Most metals share several common physical properties.

Examples: Iron, copper, aluminium, silver, and gold.

What Are the Exceptions?

Some metals behave differently from most metals.

• Sodium and potassium are soft metals that can be cut with a knife.

• Mercury is the only common metal that remains liquid at room temperature.

Where Are Metals Used in Everyday Life?

The useful properties of metals make them suitable for many applications.

• Silver foil is used on sweets.

• Aluminium foil is used for food packaging.

• Copper and aluminium are used in electrical wiring.

• Gold and silver are used for jewellery.

• Metal wires are used in musical instruments.

• Steel cables support bridges and cranes.

• School bells and ghungroos use the sonorous property of metals.

• Mercury is used in thermometers.

• Metal utensils are used for cooking because they conduct heat well.

What Are the Properties of Non-Metals?

Non-metals differ from metals in both appearance and behaviour.

Examples: Oxygen, carbon, sulphur, nitrogen, and chlorine.

Why Are Non-Metals Important?

Non-metals play essential roles in life and industry.

What Happens When Metals React with Air and Water?

Exposure to air and water can change the surface of many metals.

Rusting

Rusting is the formation of a reddish-brown coating on iron due to its reaction with oxygen and water.

Corrosion

Corrosion is the gradual deterioration of metals caused by air, water, or other substances.

Discolouration

Different metals develop different coatings:

• Iron → Rust (reddish-brown)

• Copper → Green coating

• Silver → Black coating

How Can Rusting Be Prevented?

Several methods protect metals from corrosion.

• Painting: Prevents contact with air and moisture.

• Oiling and Greasing: Forms a protective layer.

• Galvanisation: Covers iron with a layer of zinc to prevent rusting.

How Do Metals and Non-Metals React Differently?

Magnesium

• Magnesium burns with a dazzling white flame.

• It forms magnesium oxide, a basic oxide.

• Magnesium oxide turns red litmus blue after mixing with water.

Sulphur

• Sulphur burns to form sulphur dioxide.

• Sulphur dioxide dissolves in water to form sulphurous acid.

• It turns blue litmus red, showing that non-metal oxides are acidic.

Sodium and Phosphorus

• Sodium reacts vigorously with air and water, so it is stored in kerosene.

• Phosphorus catches fire easily in air and is stored under water.

What Are the Important Differences Between Metals and Non-Metals?

Metals and non-metals differ in their physical properties, conductivity, appearance, and chemical behaviour, making each suitable for different everyday uses.

Class 7 Science Chapter 4 Notes PDF

Download the CBSE Class 7 Science Chapter 4 Notes PDF to revise the properties, uses, and reactions of metals and non-metals in a concise format.

Why Choose Physics Wallah Class 7 Science Chapter 4 Notes?

Physics Wallah Class 7 Science Chapter 4 Notes present the important concepts of The World of Metals and Non-Metals in a clear and easy-to-revise format. They help you understand material properties, chemical reactions, and everyday applications while preparing for school assessments.

• Revise Metal and Non-Metal Classification: Understand how elements are grouped based on their properties.

• Compare Their Characteristics: Recall malleability, ductility, lustre, sonority, and conductivity.

• Explore Everyday Applications: Learn where common metals and non-metals are used in daily life.

• Understand Rusting and Corrosion: Revisit their causes and methods of prevention.

• Review Chemical Reactions: Remember how magnesium, sulphur, sodium, and phosphorus react with air and water.

• Differentiate Metal and Non-Metal Oxides: Understand the basic and acidic nature of their oxides.

• Strengthen Exam Revision: Quickly revise important definitions, examples, and comparison tables.

The World of Metals and Non-Metals explains how the properties of materials determine their uses in everyday life and industry. These notes help you revise the chapter’s key concepts, reactions, and applications with confidence before school examinations.

Related Resources

• CBSE Class 7 Science Syllabus

• CBSE Class 7 Science Notes

• CBSE Class 7 Science NCERT Solutions

• CBSE Class 7 Science Important Questions

• CBSE Class 7 Science Sample Papers