1. Which of the following can be beaten into thin sheets?
(a) Zinc
(b) Phosphorus
(c) Sulphur
(d) Oxygen
Ans:
Answer is a) Zinc
2. Which of the following statements is correct?
(a) All metals are ductile.
(b) All non-metals are ductile.
(c) Generally, metals are ductile.
(d) Some non-metals are ductile.
Ans:
Answer is (c) Generally, metals are ductile.
3. Fill in the blanks.
(a) Phosphorus is a very _________non-metal.
(b) Metals are _________ conductors of heat and ____________ .
(c) Iron is ____________reactive than copper.
(d) Metals react with acids to produce ____________ gas.
Ans:
(a) reactive
(b) good, electricity.
(c) more .
(d) hydrogen.
4. Mark ‘T’ if the statement is true and ‘F’ if it is false.
(a) Generally, non-metals react with acids. ( )
(b) Sodium is a very reactive metal. ( )
(c) Copper displaces zinc from zinc sulphate solution. ( )
(d) Coal can be drawn into wires. ( )
Ans:
a) False
b) True
c) False
d) False
5. Some properties are listed in the following table. Distinguish between metals and non-metals on the basis of these properties.
6. Give reasons for the following.
(a) Aluminium foils are used to wrap food items.
Ans: Aluminium is malleable and can be easily drawn into thin sheets. Additionally, it is non-reactive with food, making it ideal for wrapping and preserving food items.
(b) Immersion rods for heating liquids are made up of metallic substances.
Ans: Metals are good conductors of heat and electricity, which makes them efficient for transferring heat to the liquid during heating.
(c) Copper cannot displace zinc from its salt solution.
Ans: Zinc is more reactive than copper according to the reactivity series. Therefore, copper cannot displace zinc from its salt solution.
(d) Sodium and potassium are stored in kerosene.
Ans: Sodium and potassium are highly reactive metals that react vigorously with oxygen and water in the air, often catching fire. Storing them in kerosene prevents them from coming into contact with air or moisture, ensuring safety.
7. Can you store lemon pickle in an aluminium utensil? Explain.
Ans: No, lemon pickle cannot be stored in an aluminium utensil because the acids present in the pickle react with aluminium, leading to the formation of salts and the release of hydrogen gas. This reaction can spoil the pickle and also make it unsafe for consumption.
8. Match the substances given in Column A with their uses given in Column B.
9. What happens when
(a) Dilute sulphuric acid is poured on a copper plate?
(b) Iron nails are placed in a copper sulphate solution?
(a) Dilute sulphuric acid is poured on a copper plate?
Ans: No reaction occurs when dilute sulphuric acid is poured on a copper plate. However, when concentrated sulphuric acid is poured on a copper plate, a chemical reaction occurs, producing blue-coloured copper sulphate crystals and hydrogen gas.
Word equation:
Copper + Concentrated Sulphuric Acid → Copper Sulphate + Hydrogen
Chemical equation:
Cu + H₂SO₄ (conc.) → CuSO₄ + H₂
(b) Iron nails are placed in a copper sulphate solution?
Ans: Iron, being more reactive than copper, displaces copper from copper sulphate solution. The blue colour of copper sulphate fades, and copper gets deposited on the iron nail.
Word equation:
Iron + Copper Sulphate → Iron Sulphate + Copper
Chemical equation:
Fe + CuSO₄ → FeSO₄ + Cu
10. Saloni took a piece of burning charcoal and collected the gas evolved in a test tube.
(a) How will she find the nature of the gas?
Ans: To find the nature of the gas, add a few drops of water to the test tube containing the gas. Shake the solution well and test it with blue litmus paper. The litmus paper turns red, indicating that the gas is acidic in nature.
(b) Write down word equations of all the reactions taking place in this process.
Ans:
Burning of charcoal:
Word equation:
Charcoal (carbon) + Oxygen → Carbon dioxide
Chemical equation:
C + O₂ → CO₂
Formation of an acidic solution:
Word equation:
Carbon dioxide + Water → Carbonic acid
Chemical equation:
CO₂ + H₂O → H₂CO₃
11. One day Reeta went to a jeweller’s shop with her mother. Her mother gave old gold jewellery to the goldsmith to polish. Next day when they brought the jewellery back, they found that there was a slight loss in its weight. Can you suggest a reason for the loss in weight?
Ans:
To polish the gold ornament, it is dipped into a solution called aqua regia (a mixture of concentrated hydrochloric acid and nitric acid in a ratio of 3:1). When the gold jewellery is immersed in aqua regia, the outermost layer of gold dissolves, exposing the inner shiny layer. This dissolution of the outer layer of gold results in a slight reduction in the weight of the jewellery.