# Ch 3: Metals and Nonmetals (NCERT Solutions)

NCERT Solutions for Class 10 Science Ch 3: Metals and Nonmetals, is given below.

You will get solutions for;

• In-text questions as well as,
• Exercises questions.

So let’s dive into it!

## In-text Questions Set-1

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?

Solution:
1. Mercury is a metal that is liquid at room temperature.
2. Sodium and potassium are metals that can be cut with a knife.
3. Silver is the best conductor of heat.
4. Mercury and lead are poor conductors of heat.

2) Explain the meanings of malleable and ductile.

Solution:
Malleable: Metals that can be hammered into thin sheets are called malleable.
Ductile: Metals that can be stretched into thin wires are called ductile.

## In-text Questions Set-2

1) Why is sodium kept immersed in kerosene oil?

Solution:
Sodium is a highly reactive metal. If left exposed to air, it can react with oxygen and catch fire. To prevent this, sodium is stored in kerosene to protect it from reacting with oxygen, moisture, and carbon dioxide in the air.

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

Solution:
(i) Iron reacts with steam to produce magnetic iron oxide (Fe₃O₄) and hydrogen gas.
3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g)

(ii) Calcium reacts with water to form calcium hydroxide and hydrogen gas.
Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g)

Potassium reacts violently with cold water, producing potassium hydroxide and hydrogen gas, which catches fire.
2K(s) + 2H2O(l) → 2KOH(aq) + 2H2(g)

3) 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.
1. Which is the most reactive metal?
2. What would you observe if B is added to a solution of Copper (II) sulfate?
3. Arrange the metals A, B, C and D in the order of decreasing reactivity.

Solution:
(i) Metal B is the most reactive because it can displace iron from iron (II) sulfate.

(ii) When metal B is added to copper (II) sulfate solution, it will cause a displacement reaction, resulting in the blue color of the solution fading and a red-brown deposit of copper forming on metal B.

(iii) The reactivity of the metals decreases in the following order: B > A > C > D. Metal B is the most reactive, as it displaces iron from its salt solution. Metal A is less reactive, displacing copper, while metal C is even less reactive, only displacing silver. Metal D is the least reactive, as it cannot displace any metal from its salt solution.

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.

Solution:
When dilute HCl is added to a reactive metal, hydrogen gas is released.

Fe(s) + H2SO4(aq) → FeSO4(aq) + H2(g)

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

Solution:
Zinc is more reactive than iron, so it displaces iron from its salt solution. Ferrous sulfate (FeSO4) is pale green, but when zinc reacts with it, it turns colorless, forming zinc sulfate (ZnSO4) and iron (Fe).

Equation:
FeSO4 + Zn → ZnSO4 + Fe(s)

## In-text Questions Set-3

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

Solution:
(i) Sodium:

Oxygen:

(ii) Formation of Magnesium Oxide:
When magnesium reacts with oxygen, each magnesium atom loses two electrons to form a magnesium ion (Mg2+). Meanwhile, each oxygen atom gains two electrons to form an oxide ion (O2-).

Formation of Sodium Oxide:
Two sodium atoms each transfer their outermost electron to an oxygen atom. By losing one electron each, the sodium atoms become sodium ions (2Na+). By gaining these electrons, the oxygen atom becomes an oxide ion (O2-).

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

2) Why do ionic compounds have high melting points?

Solution:
Ionic compounds have both positive and negative charges, creating a strong force of attraction between them. This strong attraction requires a lot of heat to break, giving ionic compounds high melting points.

## In-text Questions Set-4

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

Solution:
(i) Minerals are naturally occurring compounds or elements found in the earth’s crust.
(ii) Ores are specific minerals from which metals can be extracted. For example, bauxite (Al2O3 . 2H2O) is an ore of aluminum, and copper pyrite (CuFeS2) is an ore of copper. Not all minerals are ores, but all ores are minerals.
(iii) Ores mined from the earth are mixed with sand and rocky materials, known as impurities or gangue.

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

Solution:
Gold and platinum.

3) What chemical process is used for obtaining a metal from its oxide?

Solution:
The reduction method is used to obtain metal from its oxide.
For example, zinc oxide is reduced to metallic zinc by heating with carbon:
ZnO + C → Zn + CO

## In-text Questions Set-5

1) Metallic oxides of zinc, magnesium and copper were heated with the following metals. In which cases will you find displacement reactions taking place?

Solution:
A more reactive metal can displace a less reactive metal from its oxide. Among zinc, magnesium, and copper, magnesium is the most reactive, copper is the least reactive, and zinc is in between. Displacement reactions will occur in the following cases:

2) Which metals do not corrode easily?

Solution:
Gold and platinum.

3) What are alloys?

Solution:
An alloy is a homogeneous mixture of two or more metals, or a metal and a nonmetal.

## Exercise Questions

1) Which of the following pairs will give displacement reactions?
(a) NaCl solution and copper metal
(b) MgCl2 solution and aluminum metal
(c) FeSO4 solution and silver metal
(d) AgNO3 solution and copper metal

Solution:
Option (d), which involves AgNO3 solution and copper, is the correct answer. In this reaction, copper displaces silver cations from the solution, turning them into elemental silver. As a result, copper is oxidized to Cu2+ ions and dissolves, while silver metal precipitates out. The remaining solution contains copper(II) nitrate.

The reaction can be represented as:
Cu(s) + 2AgNO3(aq) → Cu(NO3)2(aq) + 2Ag(s)

2) Which of the following methods is suitable for preventing an iron frying pan from rusting?
1. Applying grease
2. Applying paint
3. Applying a coating of zinc
4. All of the above

Solution:
Answer (c), Applying a coat of zinc

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

Solution:
Option (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.

Solution:
Option (c), Zinc is more reactive than tin.

5) 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 nonmetals?
(b) Assess the usefulness of these tests in distinguishing between metals and nonmetals.

Solution:
(a) Metals are malleable, meaning they can be easily shaped into sheets by hammering. In contrast, non-metals are brittle and break when hammered; they cannot be shaped into sheets. Metals are good conductors of electricity, so when connected with a battery, wire, and bulb, they can light up the bulb. Non-metals, however, are poor conductors and will not light up the bulb under the same conditions.

(b) These tests help demonstrate the malleability and electrical conductivity of metals and non-metals.

6) What are amphoteric oxides? Give two examples of amphoteric oxides.

Solution:
Amphoteric oxides are substances that react with both acids and bases to form salt and water. Examples include lead oxide (PbO) and aluminum oxide (Al2O3).

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

Solution:
Zinc (Zn) and magnesium (Mg) are reactive metals that can displace hydrogen from dilute acids. In contrast, gold (Au) and silver (Ag) are less reactive and cannot displace hydrogen from dilute acids.

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

Solution:
In electrolytic refining of a metal called ‘M,’ an impure, thick block of metal M serves as the anode, while a thin strip or wire of pure metal M is used as the cathode. A salt solution of metal M is used as the electrolyte.

9) Pratyush took sulfur 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.

Solution:
When sulfur powder is burned in the air, it forms sulfur dioxide (SO2).
Sulfur dioxide does not affect dry litmus paper.
It turns moist litmus paper from blue to red because SO2 reacts with water to form sulfurous acid.

The reactions are:
S(s) + O2(g) → SO2(g)
SO2(g) + H2O →H2SO3

10) State two ways to prevent the rusting of iron.

Solution:
1. Iron can be protected from rusting by coating it with rust-proof paint.
2. Applying oil or grease to iron objects keeps them from coming into contact with moist air, which prevents rust.

11) What type of oxides are formed when non-metals combine with oxygen?

Solution:
When non-metals combine with oxygen, they form either acidic or neutral oxides. For example, N2O5 and N2O3 are acidic oxides, while CO is a neutral oxide.

12) Give reasons
(a) Platinum, gold and silver are used to make jewelry.
(b) Sodium, potassium and lithium are stored under oil.
(c) Aluminum is a highly reactive metal, yet it is used to make utensils for cooking.
(d) Carbonate and sulfide ores are usually converted into oxides during the process of extraction

Solution:
(a) Platinum, gold, and silver are used in jewelry because they are very unreactive. They don’t react with air, water, or most chemicals, and they have a lot of shine. These metals are also malleable, ductile, and resistant to corrosion.

(b) Sodium, potassium, and lithium react quickly with water, producing heat and hydrogen gas that can cause a fire. To avoid contact with water and moisture in the air, these metals are stored under oil.

(c) Aluminium forms a protective layer of aluminum oxide on its surface. This layer prevents other substances from reacting with the aluminum, making it ideal for cooking utensils.

(d) It’s easier to reduce metal oxides to free metals than to reduce their carbonates or sulfides. Therefore, ores are first converted to oxides to obtain the metals more efficiently.

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.

Solution:
Tarnished copper vessels can be cleaned with lemon or tamarind because their acids dissolve the copper oxide or basic copper carbonate coating. This process restores the vessels’ shiny red-brown color, making lemon and tamarind effective cleaners.

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

Solution:

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. 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?

Solution:
The goldsmith used a solution called Aqua regia. It’s a mixture of concentrated hydrochloric acid and nitric acid in a 3:1 ratio. Aqua regia can dissolve noble metals like gold and platinum. When the top layer of a dull gold ornament is dissolved, it loses weight.

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

Solution:
Copper is used for hot water tanks instead of steel because copper does not react with water or steam, while iron can corrode when it reacts with steam.