NCERT Solutions for Class 8th Science
Chapter 4. Materials : Metals And Non-Metals
- The materials which have the property of hard, malleable, ductile, sonorous and good conductor of heat and electricity. These are called metals.examples: iron, copper, aluminium, calcium, magnesium, etc.
- The property of metals by which they can be beaten into thin sheets is called malleability.
- The property of metal by which it can be drawn into wires is called ductility.
- Metals produce ringing sounds, They are said to be sonorous.
- Some materials are soft and dull and they break down into powdery mass on tapping with hammer. They are not sonorous and are poor conductors of heat and electricity. These materials are called non-metals. Examples: sulphur, carbon, oxygen, phosphorus, etc.
- Metals like sodium and potassium are soft and can be cut with a knife.
- Mercury is the only metal which is found in liquid state at room
- General, metallic oxides are basic in nature and non-metals oxides are acidic in nature.
- Sodium metal is very reactive. It reacts vigorously with oxygen and
water therefore, stored in kerosene.
- Phosphorus is a very reactive non-metal.It catches fire if exposed to air. To prevent the contact of phosphorus with atmospheric oxygen, it is stored in water.
- Metals react with acids and produce metal salts and hydrogen gas that burns with a ‘pop’ sound.
- Metals are used in making machinery,automobiles, aeroplanes, trains, satellites, industrial gadgets, cooking utensils, water boilers, etc.
- Non-metals used in crackers,water purification process and fertilisers to enhance the growth of plants.
- More reactive metals displace less reactive metals from their compounds in aqueous solutions.