NCERT Solutions Class 8th Science Chapter – 4 Materials: Metals and Non-Metals Notes

• hard to touch.
• lustrous i.e., freshly Cut surfaces of metals have characteristic shining.
• malleable; the property of metals by which they can be beaten mW thin sheets is called malleability.
• ductile; the property of metal by which it can be drawn into wires is called ductility.
• sonorous i.e., metals produce ringing sound when struck on a hard surface.
• Good conductors of heat and electricity.

• Metals like sodium and potassium are soft and can be cut with a knife.

• Mercury is the only metal which is found in the liquid state at room temperature.

• Non-metals are soft and dull (e.g., coal and sulphur).
• Non-metals are generally brittle, i.e., they break down into a powdery mass on tapping with a hammer.
• They are not sonorous.
• They are poor conductors of heat and electricity.

Reaction with Oxygen – Both metals and non-metals when burnt in oxygen from their oxides. Oxides of metals are basic in nature while that of non-metals are generally acidic in nature e.g.,

Reaction with Water – Some metals react with water to produce metal hydroxide and hydrogen gas. Generally, non-metals do not react with water.

• Reaction with Acids: Metals react with dii. acids and produce metal salt and hydrogen gas. Generally, non-metals do not react with dil. acids.

Reaction with Bases – Metals react with bases to produce hydrogen gas.

Displacement Reaction – More reactive metals displace less reactive metals from their metal compounds in aqueous solutions.

• Metals are used in making machinery automobiles, aeroplanes. trains, satellites, industrial gadgets, cooking utensils, water boilers etc.
• Non-metals are also used in day-to-day life. Some examples are:
  • oxygen is essential for life.
  • nitrogen, phosphorus and potassium are used as fertilizers.
  • chlorine is used as a water purifier.