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Class 10 Science Chapter 3 Metals and Non-Metals
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Metals and Non-Metals
Chapter – 3
GENERAL SCIENCE
Textual Questions and Answers:
Page No – 40
Q.1. Give an example of metal which
(i) is a liquid at room temperature.
Ans: (i) Mercury.
(ii) can be easily cut with a knife.
Ans: Lithium.
(iii) in the best conductor of heat.
Ans: Silver.
(iv) is a poor conductor of heat.
Ans: Brass.
Q.2. Explain the meanings of malleable and ductile.
Ans: 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
Q.1. Why is sodium kept immersed in kerosene oil?
Ans: Sodium metal is very reactive. It reacts vigorously with oxygen and water. A lot of heat is generated in the reaction. It is therefore, stored in kerosene.
Q.2. Write equation for the reaction of
(i) iron with steam.
(ii) calcium and potassium with water.
Ans: Iron reacts with steam to form iron oxide and hydrogen gas.
The reaction occurs as follows:
(i) 3Fe + 4H₂O(g) → Fe₃O₄ + 4H₂
The reaction occurs as follows:
(ii) 2K + 2H₂O → 2KOH + H₂
Q.3. Samples of four metals A, B, C and D were takenand added to the following solution one by one. The results obtained have been tabulated as follows:
| Metal | Iron (II) sulphate | Copper (II) sulphate | Zinc sulphate | Silver nitrate |
| A | No reaction | Displacement | – | – |
| B | Displacement | – | No reaction | – |
| C | No reaction | No reaction | No reaction | Displacement |
| D | No reaction | No reaction | No reaction | No reaction |
Use the table above to answer the following questions about metals A, B, C and D.
(i) Which is the most reactive metal?
(ii) What would you observe if B is added to a solution of copper (II) sulphate?
(iii) Arrange the metals A, B, C and D in the order of decreasing reactivity.
Ans: (i) B is the most reactive metal.
(ii) B is the more reactive than iron which is more reactive than copper. Hence B is more reactive than copper. B will displace copper from its solution.
The chemical equation is –
B + CuSO₄ → Cu + BSO₄
(iii) B > A> C > D
Q.4. Which gas is produced when dilute hydrochloric acid is added to a reactive metal? Write the chemical reaction when iron reacts with dilute H₂SO₄.
Ans: Hydrogen gas is produced when dilute hydrochloric acid is added to a reactive metal.
Chemical reaction: Fe + H₂SO₄ → FeSO₄ + H₂
Q.5. What would you observe when zinc is added to a solution of iron (II) sulphate? Write the chemical reaction that takes place.
Ans: Zinc is more reactive than iron. Therefore zinc replace iron from its solution.
The chemical reaction is-
Zn + FeSO₄ → ZnSO₄ + Fe
Page – 49
Q.1. (i) Write the electron-dot structures for sodium, oxygen and magnesium.
Ans:
(a) Sodium(2,8,1) =˙Na
(b) Oxygen(2,6) =¨:O:
(c) Magnesium(2,8,2) =¨Mg.
(ii) Show the formation of Na₂O and MgO by the transfer of electrons.
Ans:
(iii) What are the ions present in these compounds?
Ans: (a) The ions present in sodium oxide (Na2O) compound are sodium ions (Na+) and oxide ions (O2-).
(b) The ions present in magnesium oxide (MgO) compound are magnesium ions (Mg2+) and oxide ions (O2-).
Q.2. Why do ionic compounds have high melting points?
Ans: In ionic compounds, oppositely charged ions are held together by strong electrostatic force of attraction. This is because a considerable amount of energy is required to break this force of attraction. That’s why ionic compounds have high melting points.
Page – 53
Q.1. Define the following terms.
(i) Mineral.
(ii) Ore.
(iii) Gangue.
Ans: Mineral: A mineral is a naturally occurring inorganic element or compound having an orderly internal structure and characteristic chemical composition, crystal form, and physical properties.
(ii) Ore: The minerals which contain a very high percentage of a particular metal and the metal can be profitably extracted from it is called ores.
(iii) Gangue: Ores mined from the earth are usually contaminated with large amounts of impurities such as soil, sand etc. called gangue.
Q.2. Name two metals which are found in nature in the free state.
Ans: 1. Gold. and
2. Platinum.
Q.3. What chemical process is used for obtaining a metal from its oxide?
Ans: An element more reactive than the metal in metal oxide is used to displace the metal from its oxide and obtain pure metal.
For example: zinc oxide is reduced to metallic zinc by heating with carbon.
Zno(s) + C(s) → 2Fe(l) + Al₂O₃(s) + Heat
Page – 55
Q.1. Metallic oxides of zinc, magnesium and copper were heated with the following metals.
| Metal | Zinc | Magnesium | Copper |
| Zinc oxide | —– | —– | —– |
| Magnesium oxide | —– | —– | —– |
| Copper oxide | —– | —– | —– |
In which cases will you find displacement reactions taking place?
Ans:
| Metal | Zinc | Magnesium | Copper |
| Zinc oxide | No | Yes | No |
| Magnesium oxide | No | No | No |
| Copper oxide | Yes | Yes | No |
Q.2. Which metals do not corrode easily?
Ans: Gold and Platinum are the metals which do not corrode easily.
Q.3. What are alloys?
Ans: An alloy is a homogeneous mixture of two or more metals, or a metal and a nonmetal.
EXERCISES
Q.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.
Ans: (d) AgNO₃ solution and copper metal.
Q.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.
Ans: (d) All of the above.
Q.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.
Ans: (a) Calcium.
Q.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.
Ans: (c) Zinc is more reactive than tin.
Q.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.
Ans: 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.
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.
Q.6. What are amphoteric oxides? Give two examples of amphoteric oxides.
Ans. An amphoteric oxide is a compound that can act as either an acid or a base. The term “amphoteric” comes from the Greek words “Amphi,” meaning “both,” and “teros,” meaning “to turn.” Amphoteric oxides are able to turn because they have both acidic and basic properties.
Examples: Aluminium oxide and zinc oxide.
Q.7. Name two metals which will displace hydrogen from dilute acids, and two metals which will not.
Ans: The two metals which will displace hydrogen from dilute acids as they are more reactive then hydrogen. Mercury and copper cannot displace hydrogen from dilute acids as they are less reactive than hydrogen.
Q.8. In the electrolytic refining of a metal M, what would you take as the anode, the cathode and the electrolyte?
Ans: Anode – Impure metal
Cathode – Pure metal
Electroliti – Metal salt solution.
Q.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?
(ii) Moist litmus paper?
Ans: (i) Dry litmus paper – No, action.
(ii) Moist litmus paper – becomes red.
(b) Write the balanced chemical equation for the reaction taking place.
S + O₂ → SO₂ + H₂O → H₂SO₃
Q.10. State two ways to prevent the rusting of iron.
Ans: (i) By painting.
(ii) By oiling.
Q.11. What type of oxides are formed when nonmetals combine with oxygen?
Ans: When nonmetals react with oxygen, they form acidic oxides or neutral oxides.
Q.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.
Ans: (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.
Q.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.
Ans: 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.
Q.14. Differentiate between metal and non-metal on the basis of their chemical properties.
Ans:
| Metals | Non-metals |
| (1) Oxides of metals are basic. | (1) Oxides of metals are are acidic. |
| (2) Metals react with water to produce metal hydroxide and hydrogen gas. | (2) Generally,non-metals do not react with water. |
| (3) Metals react with acids and produce metal Salt and hydrogen. | (3) Generally non-metals do not react with acids. |
Q.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?
Ans: 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.
Q.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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