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CBSE Notes Class 7 Science Chapter 4 The World of Metals and Non-Metals
Materials around us can be classified into metals and non-metals based on their properties. This chapter helps students understand the differences between these two groups and their uses in daily life.
Students learn that metals are usually shiny, hard, and strong. They conduct heat and electricity and can be shaped into different forms. Examples include iron, copper, and aluminum. Metals are used in making utensils, wires, machines, and buildings.Non-metals are used in various applications such as making fertilizers, medicines, and fuels.
This chapter helps students develop a better understanding of materials and their importance in daily life. It also lays the foundation for learning more about chemistry in higher classes.
1.0Download CBSE Class 7 Science Chapter 4 Notes: Free PDF
Download the CBSE Class 7 Science Chapter 4—The World of Metals and Non-Metals Notes PDF to learn about the differences, uses, and properties of metals and non-metals. There are real-life examples and easy-to-understand language used to explain the content. A useful tool for quick review and better test preparation.
2.0The World of Metals and Non-metals Class 7 Science Chapter 4 – Revision Notes
Metals and non-metals are two groups of elements with different properties. Metals are shiny, hard, malleable, ductile, sonorous and good conductors, while non-metals are mostly dull, soft or brittle and poor conductors.
Key Concepts:
- Metals: Lustrous, generally hard, malleable, ductile, sonorous and good conductors of heat and electricity.
- Non-metals: Mostly dull, soft or brittle, not malleable, not ductile, not sonorous and poor conductors.
- Exceptions: Sodium and potassium are soft enough to cut with a knife. Mercury is a liquid metal. Graphite conducts electricity. Iodine and graphite are lustrous non-metals.
- Oxides: Metal oxides are generally basic. Non-metal oxides are generally acidic.
- Corrosion: Slow damage of metals by air, water or other substances.
- Elements: Substances that cannot be broken into simpler substances. 118 are known.
Physical Properties:
- Lustre: Copper, aluminium and iron shine. Coal, sulphur and phosphorus are dull.
- Hardness: Metals are generally hard and solid. Mercury is liquid at room temperature.
- Malleability: Metals can be beaten into thin sheets, like aluminium foil. Gold and silver are the most malleable.
- Brittleness: Coal and sulphur break into pieces when hit. Wood is neither malleable nor brittle.
- Ductility: Metals can be drawn into wires for musical instruments, electrical fittings and jewellery.
- Sonority: Metals give a ringing sound, like ghungroos and school bells. Coal and sulphur give a dull sound.
- Heat conduction: Metals conduct heat well, so cooking vessels are metal with wooden or heat-resistant handles.
- Electrical conduction: Metals conduct electricity. Plastic handles and rubber gloves protect electricians because they do not conduct.
Chemical Properties of Metals:
- Rusting: Iron rusts only when both air and water are present. The brown coating is rust.
- Other corrosion: Copper gets a green layer and silver turns black.
- Prevention: Painting, oiling, greasing, galvanisation (zinc coating), tinning, electroplating, anodizing, alloying and sacrificial protection.
- Iron Pillar of Delhi: Over 1600 years old and hardly rusted.
- Magnesium in air: Burns with bright white light to form magnesium oxide, which turns red litmus blue (basic).
- Sodium: Very reactive, so it is kept in kerosene.
- Metal + Acid: Salt + hydrogen gas. Example: zinc + hydrochloric acid gives zinc chloride + hydrogen.
- Metal + Base: Most do not react. Aluminium and zinc react with strong bases like NaOH to give a salt + hydrogen.
Chemical Properties of Non-metals:
- Sulphur in air: Burns to form sulphur dioxide, which in water forms acidic sulphurous acid.
- Sulphur trioxide + water: Sulphuric acid.
- With water: Non-metals like sulphur generally do not react.
- Phosphorus: Catches fire in air, so it is kept under water.
Uses of Metals:
- Gold, silver and platinum: jewellery. Gold and silver amalgam: tooth fillings.
- Zinc: galvanisation. Iron: machines. Steel: utensils. Copper: electrical wires.
- Aluminium: utensils, foil, aeroplanes, ships, cars and overhead cables.
- Titanium, chromium, manganese and zirconium are strategic metals used in space science, atomic energy and defence.
- Iron is in haemoglobin and magnesium is in chlorophyll.
- Tin: soldering and coatings. Lead: pipes and batteries. Mercury: thermometers.
- Iron and aluminium are often recycled.
Uses of Non-metals:
- Oxygen: breathing.
- Sulphur: sulphuric acid, matchboxes, gunpowder and rubber vulcanisation.
- Carbon: part of proteins, fats and carbohydrates. Graphite is a dry lubricant.
- Phosphorus and nitrogen: fertilisers.
- Hydrogen: makes ammonia, converts vegetable oil to vegetable ghee and is rocket fuel.
- Chlorine and bleaching powder: water purification. Iodine: antiseptic.
3.0Chapter 4 Terminologies to Know – The World of Metals and Non-metals:
- Lustre: Shine.
- Malleability: Ability to be beaten into thin sheets.
- Ductility: Ability to be drawn into wires.
- Brittle: Breaks into pieces when hit.
- Sonorous: Produces a ringing sound.
- Conductor: Allows heat or electricity to pass through.
- Hardness: Ability to resist scratching, cutting or bending.
- Element: A substance that cannot be broken into simpler substances.
- Rust: Brown coating on iron.
- Corrosion: Slow damage of metals by air, water or other substances.
- Galvanisation: Coating iron with zinc.
- Alloy: A mixture of metals, or of metals with non-metals.
- Steel: Mixture of iron and carbon.
- Metallurgy: Extracting and refining metals from ores.
4.0Learning Guide for Class 7 Science – The World of Metals and Non-metals:
- Hammering Activity: Hammer copper, aluminium, iron, sulphur, coal and phosphorus. Observation: Metals are shiny and flatten. Non-metals are dull and break.
- Ringing Sound Activity: Drop a metal plate, a coin, coal and sulphur. Observation: Metals ring. Coal and sulphur sound dull.
- Heat Conduction Activity: Dip a metal spoon and a wooden spoon in hot water. Observation: The metal spoon gets hotter.
- Electrical Conduction Activity: Test materials in a battery and bulb circuit. Observation: The bulb glows for aluminium foil, iron nail and copper wire only.
- Rusting Activity: Keep nails for 8 to 10 days in three bottles: dry air with silica gel (A), boiled water with oil (B), and water with air (C). Observation: Only nails in C rust, so both air and water are needed.
- Magnesium Activity: Burn magnesium ribbon, add warm water to the ash and test with litmus. Observation: Red litmus turns blue, so it is basic.
- Burning Sulphur Activity: Burn sulphur in a jar, add water and test with litmus. Observation: The solution is acidic.
- Sulphur in Water Activity: Add water to sulphur powder. Observation: No reaction.
Everyday Examples:
- Aluminium foil for wrapping food.
- Cooking vessels with wooden handles.
- Ghungroos and school bells.
- Rusty iron kept outdoors.
- Smartphones use metals like copper, gold and lithium, and non-metals like silicon and graphite.
Revision Tips:
- Metals are shiny, hard, malleable, ductile, sonorous and good conductors. Non-metals are mostly the opposite.
- Metal oxides are basic. Non-metal oxides are acidic.
- Rusting needs both air and water.
- Remember the exceptions: sodium, potassium, mercury, graphite and iodine.
- Plastic, glass, wood, rubber and paper are not non-metals because they are not elements.
Safety Rules:
- Do the hammering activity with a teacher or an adult.
- Be careful while dropping objects and holding hot water.
- Wear eye protection and keep a safe distance when burning magnesium.
- Burn sulphur only in a fume hood or well-ventilated area.
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8.0Key Features of Chapter 4: The World of Metals and Non-metals
- Classification of Elements: This separates metals from non-metals based on their physical and chemical properties.
- Physical Properties: Talks about metals' hardness, lustre, malleability, and conductivity, among other things.
- Chemical Properties: The result tells you how metals and non-metals react with acids, water, and oxygen.
- Uses in Everyday Life: Talks about how metals are used in wires and utensils and how non-metals are used in fuels and fertilisers.
- Corrosion and Prevention: Talks about rusting and how to stop it with things like painting and galvanisation.
- Industrial Importance: Shows how metals and non-metals are important for making things and building things.