Science Class 10 Chapter 3 NCERT Solutions

Class 10 Science Chapter 3 — Metals and Non-Metals — is an essential topic that helps students understand the physical and chemical properties of metals and non-metals, their uses, reactions, and differences. NCERT Solutions for this chapter provide step-by-step explanations to help students clear their concepts and score better in exams.

Science Class 10 Chapter 3 NCERT Solutions

1. Give an example of a metal which
(i) is a liquid at room temperature.
(ii) can be easily cut with a knife.
(iii) is the best conductor of heat.
(iv) is a poor conductor of heat.

Answer:

(i) Liquid at room temperatur: Mercuty (Hg)
(ii) Easily cut with a knife: Sodium (Na)
(iii) Best conductor of heat: Silver (Ag)
(iv) Poor conductor of heat: Lead (Pb)

2. Explain the meanings of malleable and ductile.

Answer:

  • Malleable: If the metal can be pressed or hammered into thin sheets is known as malleable. For example, Gold can be made into very thin sheets.
  • Ductile: If the metal is stretched into long wire is known as ductile. For example, Copper is used to make electric wires.

3. Why is sodium kept immersed in kerosene oil?

Answer: Sodium is very reactive metal and reacts quickly with air (oxygen) and moisture (water vapor). If the Sodium keep open then it can catch fire, so it is stored in kerosene oil to stop it from touching air or water.

4. Write equations for the reactions of
(i) iron with steam
(ii) calcium and potassium with water

Answer: The equations for the reactions are:

  • When the iron is heated with steam then it forms iron oxide and hydrogen gas. The equation is:
    3Fe + 4H2O (steam) -> Fe3O4 + 4H2
  • Calcium reacts solowly with cold water to form calcium hydroxide and hydrogen gas. The equation is:
    Ca + 2H2O -> Ca(OH)2 + H2
  • The potassium reacts very fast and violently with water to form potassium hydroxide and hydrogen gas. The equation is:
    2K + 2H2O -> 2KOH + H2

5. Samples of four metals A, B, C and D were taken and added to the following solution one by one. The results obtained have been tabulated as follows.

Samples of four metals A, B, C and D were taken and added to the following solution one by one. The results obtained have been tabulated as follows

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.

Answer:

(i) Metal B is the most reactive
(ii) No reaction will happen
(iii) The arrangement will be

  • B → displaces iron
  • A → displaces copper
  • C → displaces silver
  • D → no reaction with any solution
  • Final order: B > A > C > D

6. Which gas is produced when dilute hydrochloric acid is added to a reactive metal? Write the chemical reaction when iron reacts with dilute H2SO4.

Answer: When dilute hydrochloric acid (HCl) is added to a reactive methal, it produces: Hydrogen gas (H2), this gas comes out as bubbles. Iron reacts with dilute sulphuric acid (H2SO4), reaction: Fe + H2SO4 + H2

7. What would you observe when zinc is added to a solution of iron(II) sulphate? Write the chemical reaction that takes place.

Answer: The Zinc is more reactive than iron, So, zinc will push out iron from the solution, this is a displacement reaction. The solution changes color from pale green to colorless. A brown deposit of iron forms on the zinc. Bubbles may appear if water is involved.

8. (i) Write the electron-dot structures for sodium, oxygen and magnesium.
(ii) Show the formation of Na2O and MgO by the transfer of electrons.
(iii) What are the ions present in these compounds?

Answer:

(i) These show only the valence electrons of each atom.
Sodium (Na) -> 1 dot
Magnesium (Mg) -> 2 dots
Oxygen (O) -> 6 dots

(ii) Na2O (Sodium oxide): Each sodium atom gives 1 electron to oxygen. Oxygen need 2 electrons, so the 2 sodium atoms are needed. 2Na -> 2Na+ + 2e O + 2e -> O2
MgO (Magnesium oxide): Magnesium gives 2 electrons to oxygen, so only 1 magnesium atom is needed. Mg -> Mg2+ + 2e O + 2e– -> O2-

(iii) The ions present in sodium oxide compound (Na2O) are sodium ions (2Na+) and oxide ions (O2-). The ions present in Magnesium oxide compound (MgO) are magnesium ions Mg2+ and oxide ions (O2-).

9. Why do ionic compounds have high melting points?

Answer: The Ionic compounds are made of pasitive and negative ions. These ions are storngly stick together like magnets pulling each other. To melt this compounds we need to break this bond because of thi we have to give lot of heat to break this bond.

10. Define the following terms.
(i) Mineral (ii) Ore (iii) Gangue

Answer:

  • (i) Mineral: A mineral is a natural substance found in the earth that contains metal or non-metal like bauxite contains aluminium.
  • (ii) Ore: An ore is a mineral from which we can easily and profitably extrat metal like bauxite is the ore of aluminium.
  • (iii) Gangue: Gangue is the waste material mixed with the ore. We remove gangue during the cleaning of ore.

11. Name two metals which are found in nature in the free state.

Answer: The metal found in nature are very unreactive because they do not combine with other elements. For example, Gold (Au), Silver (Ag).

12. What chemical process is used for obtaining a metal from its oxide?

Answer: The chemical process to get metal from its oxide is known as reduction. Reduction remove oxygen from the metal oxide to get pure metal. For example, ZnO + C -> Zn + CO here, carbon removes oxygen from zinc oxide giving zinc metal.

13. Metallic oxides of zinc, magnesium and copper were heated with the following metals.

Metallic oxides of zinc, magnesium and copper were heated with the

In which cases will you find displacement reactions taking place?

Answer: A more reactive metal removes a less reactive metal from its oxide. The reactions will take place when:

  • Magnesium + Zinc oxide
  • Magnesium + Copper oxide
  • Zinc + Copper oxide

Beacuse the magnesium is more reactive than zinc and copper and Zinc is more reactive than copper.

14. Which metals do not corrode easily?

Answer: Some metals do not react with air or water so they stay shiny and strong for a long time like Gold and platinum. These metal is known as noble metal.

15. What are alloys?

Answer: An alloy is a mixture of two or more metals like steel (Iron and carbon), Bronze (Copper and Tin). This type of metal is better than pure metals.

16. 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.
Explanation: Reaction happens, Copper is more reactive than silver.

17. 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

18. 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

19. 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.

20. You are given a hammer, a battery, a bulb, 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 non-metals.

Answer:

  • (a) Metals can be beaten into this sheets using a hammer, Non-metals break into small pieces when hammered are used. Metal are good conductors of electricit, if you connect battery, bulb and wires then the bulb lights up. Non-metals are non-conductors, if you connect bulbe using non-metal then bulb will not glow.
  • (b) These tests are simple and efective for basic identification of malleability and Electrocial conductivity.

21. What are amphoteric oxides? Give two examples of amphoteric oxides.

Answer: The amphoteric oxides are oxides that can react with both acids and bases to form salt and water. They show dual behavior, For example, Aluminum oxide (Al2O3) and Zinc oxide (ZnO). These oxides react with Acids -> act like bases and Bases -> act like acids.

22. Name two metals which will displace hydrogen from dilute acids, and two metals which will not.

Answer: The metals that will displace hydrogen from dilute acids are:

  • Zinc (Zn)
  • Iron (Fe)

These metal are ractive, they can react with acids and release hydrogen gas.

The metals that will not displace hydrogen are:

  • Copper (Cu)
  • Silver (Ag)

These are less reactive and do not ract with dilute acids.

23. In the electrolytic refining of a metal M, what would you take as the anode, the cathode and the electrolyte?

Answer: We can purify metal M using electricity, we use three things:

  • Anode -> Thick block of impure metal M
  • Cathode -> Thin strip of pure metal M
  • Mlectrolyte -> A solution of a salt of metal M

Impure metal M at the anode dissolves into the solution, pure metal M gets deposited on the cathode and impurites falls down as anode mud.

24. 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?
(b) Write a balanced chemical equation for the reaction taking place.

Answer: When the sulphur heated in air then it react with oxygen and forms a gas called sulphur dioxide (SO2). SO2 is a non-metal oxide and it is acidic in nature.
(a)

  • (i) Nothing happen. The gas do not ract with dry paper.
  • (ii) In this condition the gas turns blue litmus paper to red due to SO2 dissolves in water and forms an acid called sulphurous acid (H2SO3). Acids turn blue litmus paper to red.

(b) S (solid) + O2 (gas) -> SO2 (gas)

25. State two ways to prevent the rusting of iron.

Answer:

  • Using paint or coating: Apply paint, oil, grease or plastic coating to create a barrier between iron and moisture/oxygen.
  • Galvanization: Iron is coated with a thin layer of zinc, Zinc protects iron by corroding first, this process is called sacrificial protection and keeping the iron safe.

26. What type of oxides are formed when non-metals combine with oxygen?

Answer: When the non-metals combine with oxygen then it form acidic oxides or neutral oxides, depending on the element involved and the conditions of the reaction. The types of oxides formed are:

a. Acidic Oxides: These oxides dissolve in water to form acids and turn blue litmus paper red. For example,

  • Carbon dioxide (CO2) -> forms carbonic acid (H2CO3)
  • Sulphur dioxide (SO2) -> forms sulphurous acid (H2SO3)
  • Nitrogen dioxide (NO2) -> forms nitric acid (HNO3)

b. Neutral oxides: These oxides do not react with acids or bases and have no effect on litmus paper. For example,

  • Carbon monoxide (CO)
  • Nitrous oxide (N2O)
  • Water (H2O)

27. Give reasons
(a) Platinum, gold and silver are used to make jewellery.
(b) Sodium, potassium and lithium are stored under oil.
(c) Aluminium is a 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)The platinum, goal and silver do not rust or react with air or water and look shiny and beautiful. They can be easy to shape int righs and nechlaces.
  • (b) Sodium, potassium and lithium is very dangerous when the come in contact of water or air, they can catch fire. Oil protects them by keeping air and water away.
  • (c) Aluminimu quickly forms a protective layer on its surface and this layer stops if from reaction. It is also light weight, cheap and heats up fast which is good for cooking.
  • (d) It is easier to get metal from oxides and this oxides can heated with carbon to remove oxygen and get pure metal.

28. 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: The Lemon and tamarind contain citric acid and tartaric acid. These acids react with the basic copper carbonate and dissolve it. This chemical reaction removes the green layer and helps to make original sine.

29. Differentiate between metal and non-metal on the basis of their chemical properties.

Answer:

Metals (like iron, copper, aluminium)

  • React with oxygen → form basic oxides Example: Magnesium + Oxygen → Magnesium oxide (MgO)
  • React with acids → produce hydrogen gas Example: Zinc + Hydrochloric acid → Zinc chloride + Hydrogen
  • Lose electrons → form positive ions

Non-metals (like carbon, sulphur, nitrogen)

  • React with oxygen → form acidic oxides Example: Sulphur + Oxygen → Sulphur dioxide (SO₂)
  • Do not react with acids (They don’t produce hydrogen gas)
  • Gain electrons → form negative ions

30. 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. The 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: The mysterious solution that made the bangles sparkle but also reduced their weight was almost certainly aqua regia. Aqua Regia is a mixture of concentrated hydrochloric acid (HCl) and concentrated nitric acid (HNO3) in a 3:1 ratio. The name become “Royal Water” because it can dissolve noble metals like gold and platinum.

31. Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron).

Answer: The copper is used for hot water tanks due to:

  • Copper does not react with hot water
  • Copper conducts heat better
  • Copper resists corrosion

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