Class 10 Science
Chapter 3: Metals and Non-metals
Textual Questions and Answers
Page - 40
1. Give an example of a metal that:
(i) Is a liquid at room temperature.
Answer: Mercury.
(ii) Can be easily cut with a knife.
Answer: Lithium.
(iii) Is the best conductor of heat.
Answer: Silver.
(iv) Is a poor conductor of heat.
Answer: Brass.
2. Explain the meanings of malleable and ductile.
Answer:
Malleable: Substances that can be beaten into thin sheets are called malleable. For example, most of the metals are malleable.
Ductile: Substances that can be drawn into thin wires are called ductile. For example, most of the metals are ductile.
Page - 46
1. Why is sodium kept immersed in kerosene oil?
Answer: Sodium is highly reactive with oxygen and water, producing heat. To prevent this reaction, it is stored in kerosene oil.
2. Write the chemical equations for the reactions of:
(i) Iron with steam:
3Fe + 4H₂O (g) → Fe₃O₄ + 4H₂
(ii) Calcium and potassium with water:
2K + 2H₂O → 2KOH + H₂
3. Given a table of reactivity for four metals (A, B, C, D), answer the following:
(i) Which is the most reactive metal?
Answer: B.
(ii) What happens if B is added to copper (II) sulphate solution?
Answer: B displaces copper, forming BSO₄.
Equation: B + CuSO₄ → Cu + BSO₄
(iii) Arrange the metals in decreasing reactivity order.
Answer: B > A > C > D.
4. Which gas is produced when dilute hydrochloric acid is added to a reactive metal?
Answer: Hydrogen gas.
Reaction: Fe + H₂SO₄ → FeSO₄ + H₂
5. What happens when zinc is added to iron (II) sulphate solution?
Answer: Zinc, being more reactive, displaces iron.
Reaction: Zn + FeSO₄ → ZnSO₄ + Fe
Page - 49
1.(i) Write the electron-dot structures for sodium, oxygen, and magnesium.
Answer:
(ii) Show the formation of Na₂O and MgO by the transfer of electrons.
(iii) What are the ions present in these compounds?:
Answer: (a)
Sodium oxide (Na₂O): Na⁺ and O²⁻.
(b) Magnesium oxide (MgO): Mg²⁺ and O²⁻.
2. Why do ionic compounds have high melting points?
Answer: They are held by strong electrostatic forces requiring high energy to break.
Page - 53
1. Define: (i)
Mineral: Naturally occurring inorganic substances with a specific composition.
(ii) Ore: Minerals with high metal content that can be extracted profitably.
(iii) Gangue: Impurities in ores like soil and sand.
2. Name two metals found free in nature.
Answer: Gold and Platinum.
3. Which chemical process extracts metals from oxides?
Answer: Reduction by a more reactive element, e.g., ZnO + C → Zn + CO.
Page - 55
1. Metallic oxides of zinc, magnesium and copper were heated with the following metals.
In which cases will you find displacement reactions taking place?
2. Which metals do not corrode easily?
Answer: Gold and Platinum.
3. What are alloys?
Answer: Mixtures of two or more metals, or a metal with a non-metal.
Exercises
1. Which of the following pairs will give displacement reactions?(a) Nacl solution and copper metal.
(b) MgCl2 solution and aluminium metal.
(c) FeSO4 solution and silver metal.
(d) AgNO3 solution and copper metal.
Answer: (d) AgNO3 solution and copper metal.
2. Which of the following methods is suitable for preventing an iron frying pan from rusting?
(a) Applying grease.
(b) Applying paint.
(c) Applying a coating of zinc.
(d) all of the above.
Answer: (d) All of the above.
3. An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be.
(a) Calcium.
(b) Carbon.
(c) Silicon.
(d) iron.
Answer: (a) Calcium.
4. Food cans are coated with tin and not with zinc because.
(a) Zinc is costlier than tin.
(b) Zinc has a higher melting point than tin.
(c) Zinc is more reactive than tin.
(d) Zinc is less reactive than tin.
Answer: (c) Zinc is more reactive than tin.
5. You are given a hammer, a battery, a bulls, wires and a switch.
(a) How could you use them to distinguish between samples of metals and non-metals?
(b) Assess the usefulness of these tests in distinguishing between metals and nonmetals.
Answer:
Metals can be beaten into thin sheets when it strike with a hemmer. But in a non-metal when it strike with a hammer it becomes Powder.
(a) When metals connected into circuit using battery bulb, wires and switch current passes through the circuit and bulb glows while in a non-metal no current will pass through the circuit.
(b) Hammer is a reliable method because no non-metal can be spread in to sheet because non-metal carbon in the form of graphite is a conductor of electricity.
6. What are amphoteric oxides? Give two examples.
Answer: Oxides that react with both acids and bases, e.g., Al₂O₃, ZnO.
7. Name two metals which will displace hydrogen from dilute acids, and two metals which will not.
Answer: Sodium, Zinc (can); Copper, Mercury (cannot).
8. In the electrolytic refining of a metal M, what would you take as the anode, the cathode and the electrolyte?
Answer
Anode: Impure metal.
Cathode: Pure metal.
Electrolyte: Metal salt solution.
9. Pratyush took sulphur powder on a spatula and heated it. He collected the gas evolved by inverting a test tube over it, as shown in figure below?
(a) What will be the action of gas on
(i) Dry litmus paper: No change.
(ii) Moist litmus paper: Turns red.
(b) Write the balanced chemical equation for the reaction taking place.
Answer: Reaction: S + O₂ → SO₂; SO₂ + H₂O → H₂SO₃.
10. State two ways to prevent the rusting of iron?
Answer: (i) Painting, (ii) Oiling.
11. What type of oxides are formed when non-metals combine with oxygen?
Answer: Acidic or neutral oxides.
12. Give reasons:
(a) Platinum, gold and silver are used to make jewellery.
(b) Sodium, Potassium and lithium are stored under oil.
(c) Aluminium is highly reactive metal. Yet it is used to make utensils for cooking.
(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction.
Answer: (a) Because they are non-reactive and they have shining surface.
(b) Sodium, Potassium and lithium react so vigorously that they catch fire if kept in the open. Hence, to protect them and to prevent accidental fires, they are kept immersed in kerosene oil.
(c) The surface of aluminium covered with a thin layer of oxide. The protective oxide layer prevent the aluminium from further oxidation.
(d) It is easier to reduce oxides into metal.
13. You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. explain why these sour substances are effective in cleaning the vessels.
Answer: Copper reacts with moist carbon dioxide in air to form copper carbonate and as a result, copper vessel loses its shiny brown surface forming a green layer of copper carbonate. Since Copper Carbonate dissolves in mild acids of lemon or tamarind juice, copper vessels are cleaned.
14. Differentiate between metal and non-metal on the basis of their chemical properties.
Answer:
15. A man went door to door posing as a goldsmith. He promised to bring back the glitter of old and dull gold ornaments. An unsuspecting lady gave a set of gold bangles to him which he dipped in a particular solution. The bangles sparkled like new but their weight was reduced drastically. They lady was upset but after a futile argument the man beat a hasty retreat. Can you play the detective to find out the nature of the solution he had used?
Answer: Aqua regia, is a freshly prepared mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio of 3:1; since it dissolves gold.
16. Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron).
Ans: Steel (an alloy of iron) reacts with hot water.
The chemical reaction is
3Fe(s) + 4H2O → Fe3O4 (s) + 4H2(g)
But copper does not react with hot water
Cu (s) + H2O → No reaction
Therefore copper is used to make hot water tanks.
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