CBSE Class 7 Science Notes Chapter 4 - Metals and Non-Metals PDF Download

Materials around us are made of different elements with unique properties and uses. These CBSE Class 7 Science Notes Chapter 4 explain metals and non-metals, their characteristics, applications, and reactions with air and water in a simple and easy-to-understand format.

The chapter also covers important concepts like rusting, corrosion, malleability, ductility, and conductivity. CBSE Class 7 Science Notes Chapter 4 helps students revise important topics quickly and prepare better for exams.

The World Of Metals And Non-metals Class 7 Notes

Below are The World Of Metals And Non-metals Class 7 Notes: 

1. Introduction

2. Properties of Materials

Properties of most Metals

1. Malleability

2. Ductility

3. Sonority

4. Metallic luster

5. Hardness

6. Conduction of Heat

7. Conduction of Electricity

Some examples of metals- Iron, copper, aluminium, silver, gold, etc.

Points to Remember

• Malleability- property of being beaten into thin sheets

• Ductility- property of being drawn into wires

• Sonority- property of producing a ringing sound

• Metallic Luster- metals have a lustrous (shiny) appearance

• Metals are generally hard solids.

• Metals are good conductors of heat and are therefore used in making utensils, heating appliances etc.

• Metals are good conductors of electricity and are therefore used in making electric wires, appliances etc.

Exceptions

1. Some metals like sodium and potassium are so soft that they can be cut with a knife.

2. Mercury, a metal, is liquid at room temperature.

Applications of Metals

1. Thin foils of silver are put on some Indian sweets.

2. Aluminium foils are used for wrapping food items.

3. Wires of metals like copper and aluminium are used in electrical fittings.

4. Some ornaments like bangles, necklaces, earrings etc., are also made from metal wires.

5. Metal wires play important functions in a variety of stringed musical instruments, such as veena, sitar, violin and guitar.

6. Tea strainers are made with metal wires.

7. Mercury is used in thermometers, for measurement of temperature.

8. Steel (a mixture of iron and carbon) wires, that can support heavy loads, are used in bridges and cranes.

9. The school bell, that makes a ringing sound, is made of metal.

10. The stick used by blind people to sense objects in their path is made of metal.

11. Gurugrus, which are supposed to make a ringing sound when struck, are made of metals.

12. Metal vessels are used for cooking, because metals are good conductors of heat.

Properties of most Non-Metals

1. Brittle

2. Cannot be drawn into wires alone

3. Usually soft and dull in appearance

4. Non-lustrous

5. Non-sonorous

6. Poor conductors of heat

7. Poor conductors of electricity

Some examples of Non-Metals- Oxygen, Carbon, Sulphur, Nitrogen, etc.

Applications/Importance of Non-Metals

1. Oxygen, that we all breathe in, is non-metal and is essential for our survival.

2. Carbon is the building block of all life forms.

3. Nitrogen is an essential nutrient for plant growth.

4. Nitrogen is also used in manufacturing fertilizers.

5. Chlorine, a non-metal, is generally used in water purification.

6. A solution of iodine, a non-metal, is applied on wounds as an antiseptic.

3. Effects of Air and Water on Metals and Non-Metals

1. Iron objects, when exposed to open atmosphere, develop reddish brown deposit on their surfaces. This is due to a chemical reaction involving iron metal, oxygen and water.
   The reddish-brown deposit is called rust. The process of formation of rust on objects made of iron is called rusting.

2. Many other metals also exhibit discolouration when kept open in the atmosphere. Formation of a green coating on the surface of copper objects or a black coating on the surface of silver objects are a few examples.

3. Gradual deterioration of metal surfaces caused by air, water, or other substances is known as corrosion.

4. Rusting of iron, which is a serious problem, can be prevented by several methods such as painting, oiling, greasing, and applying a protective layer of zinc metal on iron (galvanization).

5. Magnesium ribbon burns (in presence of oxygen) with a dazzling white flame and changes into a white powder.

6. When this white powder is mixed with water, and tested with litmus, red litmus turns blue. This suggests that white powder (oxide of magnesium) is basic in nature.

7. Therefore, metals react with oxygen to produce metal oxides which are basic in nature.

8. Sodium, a metal, reacts vigorously with oxygen and water, and is hence stored in kerosene.

9. On burning sulphur, a non-metal, in air (oxygen), sulphur dioxide gas is formed. On dissolving sulphur dioxide gas in water, sulphurous acid is formed which turns blue litmus red.

10. Non-metals react with oxygen to produce oxides which are acidic in nature.

11. Generally, non-metals do not react with water.

12. Phosphorus, a non-metal, is covered in water as it catches fire when exposed to atmospheric air.

Some more points to remember

Materials such as plastic, rubber, wood and paper are not classified as metals and non-metals because they are not pure elements.

Plastic, wood, rubber are poor conductors of heat and electricity, and therefore plastic coverings are used on screwdrivers and rubber gloves are used by electricians. These help protect electricians from electric shock.

4. Some interesting facts!

1. Gold and silver are the most malleable metals.

2. Gold is so ductile that one gram of it can be drawn into a 2-kilometer-long wire!

3. Many metals and their alloys (mixtures of two or more metals or a metal and a non-metal) are important for daily use in utensils and tools. These are also important for modern technologies and essential in almost every industry. Some special metals are also used in atomic energy (such as zirconium), aerospace (titanium), etc.

4. In India, many metals, especially iron and aluminium, are recycled to minimise waste and contribute to sustainability.

Note- Discussion on metalloids, right now, is out of the scope of this chapter. Properties of metalloids shall be discussed in higher grades.

The World Of Metals And Non-metals Notes PDF

Students can download The World Of Metals And Non-metals Notes PDF for effective revision. The PDF includes important concepts like properties of metals and non-metals, rusting, corrosion, and reactions with air and water in simple language. These CBSE Class 7 Science Notes Chapter 4 are especially useful during exams when students need fast revision of definitions, properties, and important concepts. 

The World Of Metals And Non-metals Class 7 Science Notes PDF

How to Use The World Of Metals And Non-metals Class 7 Notes for Exam Preparation

The World Of Metals And Non-metals Class 7 Notes help students revise important concepts in a simple and organized way. Regular revision with CBSE Class 7 Science Notes Chapter 4 improves understanding of properties, uses, and reactions of metals and non-metals.

• Revise important properties of metals and non-metals regularly.

• Learn definitions like malleability, ductility, and corrosion carefully.

• Practice examples of metals and non-metals used in daily life.

• Understand rusting and methods to prevent it.

• Use The World Of Metals And Non-metals Class 7 Science Notes for quick revision before tests and exams.