1. White phosphorous has to be kept in water. Why
Ans: Phosphorus is to be kept in water to prevent its contact with air because it is highly reactive.

2. Write short notes on: Uses of common metals and non-metals
Ans: Uses of common metals and non-metals :
Uses of metals – for making machinery, automobiles, industrial gadgets, building, bridges, cooking utensils, electrical gadgets, jewellery, sheets.
Uses of non-metals – oxygen is used by plants and animals for their survival, nitrogen is used by plants for their growth, chlorine is used in water purification to kill germs, sulphur is used for making sulphuric acid, tincture iodine has antiseptic properties.

3. Write short note on Noble metals.
Ans: Noble metals – Gold, silver and platinum are noble metals. They occur free in nature. and maintain their luster for a long time. Platinum, gold and silver are used for making jewellery as they do not tarnish

4. Give two uses of sulphur in chemical industry.
Ans: It is used in the manufacture of sulphuric acid. It is used in the manufacture of carbon disulphide, which is used as an industrial solvent.

5. How is sulphur useful in medicine.
Ans: Sulphur is the main constituent of skin ointments. Metallic sulphides of sulphur are used in the preparation of Ayurvedic medicines.

6: Give two uses of gold.
Ans: Gold is used for making ornaments. Gold foils are used in the preparation of Ayurvedic medicines.

7. You are given two materials X and Y. On hammering X is flattened, but Y breaks. Which one is a metal
Ans: X is a metal because it flattens, i.e.  it is malleable.

8. There are four materials A, B, C and D. A and D are hard and shiny, but B and C are dull and not very hard. Identify the metals and non-metals from A, B, C and D.
Ans: A and D are metals.  B and C are non-metals.

9. Gaurav knows that wires can be made from copper and aluminium. He tries to make wire from sulphur and carbon. Will he succeed give reason.
Ans: No, he will not succeed because sulphur and carbon are non-metals. Non-metals are not ductile, that is, they cannot be drawn into wires.

10. Identify the most reactive and least reactive metal amongst the followings:
Al, K, Cu, and Au.
Ans: Most reactive metal is K and least reactive metal is Au.

11. An iron knife kept dipped in blue copper sulphate solution changes to light green. Why.
Ans: This is because iron replaces copper from copper sulphate and forms iron sulphate because iron is more reactive than copper.

12. Name the soft metal which can be cut with a knife.
Ans: Sodium, potassium.

13. Name one metal which is not malleable.
Ans: Zinc or arsenic.

14.What would happen to iron railings if they are not painted Ans:
Ans: They will get rusted.