TEXTBOOK QUESTION–ANSWERS WITH EXPLANATION

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SECTION – PAGE QUESTIONS

Page 40 – Questions

Q1. 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:

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Q2. Explain the meanings of malleable and ductile.

Answer

• Malleable → metals can be beaten into thin sheets (e.g., aluminium foil).

• Ductile → metals can be drawn into thin wires (e.g., copper wires).

SECTION – CHEMICAL PROPERTIES OF METALS (Page 46)

Q1. Why is sodium kept immersed in kerosene oil?

Answer:
Sodium reacts violently with oxygen and water, producing heat and hydrogen gas.
To prevent accidental fire, it is stored under kerosene.

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Q2. Write equations for reactions of

(i) Iron with steam
(ii) Calcium and potassium with water

Answer

(i)

$$3Fe+4H_{2}O\stackrel{steam}{\to }F{e}_3{O}_4+4H_2\uparrow$$

(ii)

$$Ca+2H_{2}O\to Ca(OH{)}_2+H_2\uparrow$$
$$2K+2H_{2}O\to 2KOH+H_2\uparrow +\text{heat}$$

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Q3. Table of metals A, B, C, D

Answers

(i) Most reactive metal = B (displaces Fe)
(ii) When B added to CuSO₄ → reddish brown copper is deposited
(iii) Decreasing reactivity order: B > A > C > D

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Q4. Which gas is produced when dilute HCl is added to a reactive metal? Write reaction for Fe + H₂SO₄.

Answer

Gas released = Hydrogen (H₂)

$$Fe+H_{2}S{O}_4\to FeS{O}_4+H_2\uparrow$$

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Q5. What would you observe when zinc is added to iron(II) sulphate solution?

Answer

Zinc is more reactive than iron, so it displaces iron.

$$Zn+FeS{O}_4\to ZnS{O}_4+Fe$$

Appearance: brown iron deposits, solution fades from green

PAGE NO. 49 – QUESTIONS & ANSWERS

Q1. (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?**

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Answer:

(i) Electron-dot structures

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(ii) Formation of Na₂O and MgO

Formation of Sodium Oxide (Na₂O)

1. Sodium loses one electron each to become Na⁺

$$2Na\to 2N{a}^{+}+2e^{-}$$

2. Oxygen gains two electrons to become O²⁻

$$O+2e^{-}\to O^{2-}$$

3. Combination

$$2N{a}^{+}+O^{2-}\to N{a}_{2}O$$

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Formation of Magnesium Oxide (MgO)

1. Magnesium loses two electrons

$$Mg\to M{g}^{2+}+2e^{-}$$

2. Oxygen gains two electrons

$$O+2e^{-}\to O^{2-}$$

3. Combination

$$M{g}^{2+}+O^{2-}\to MgO$$

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(iii) Ions present in these compounds

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Q2. Why do ionic compounds have high melting points?

Answer:

Ionic compounds have high melting points because the strong electrostatic forces of attraction between the oppositely charged ions require a large amount of energy to break.
Therefore, ionic compounds are usually solid at room temperature and have very high melting and boiling points.

PAGE NO. 53 – QUESTIONS & ANSWERS

Q1. Define the following terms:

(i) Mineral

A mineral is a naturally occurring substance found in the earth’s crust that contains one or more metals or their compounds.

(ii) Ore

An ore is a mineral from which a metal can be profitably extracted.

(iii) Gangue

Gangue refers to the impurities such as sand, soil, and rocky materials that are present in the ore and must be removed before metal extraction.

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Q2. Name two metals which are found in nature in the free state.

Answer:

Gold and Silver

Explanation:
These metals are least reactive and do not combine with other elements, so they are found in free or native form.

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Q3. What chemical process is used for obtaining a metal from its oxide?

Answer:

The process used is called reduction.

Explanation:

In reduction, oxygen is removed from metal oxide to obtain the pure metal.
Example:

$$ZnO+C\to Zn+CO$$

PAGE NO. 55 – Question & Answer 

Q1. Metallic oxides of zinc, magnesium and copper were heated with the following metals.

In which cases will you find displacement reactions taking place?

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Answer:

To determine displacement reactions, we use the reactivity series:

$$\text{Most reactive: }Mg>Zn>Cu\text{ : Least reactive}$$

Rule:

A more reactive metal can displace a less reactive metal from its oxide.

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Case-by-case outcomes

1. Zinc heated with Zinc oxide

No reaction — a metal cannot displace itself.

2. Zinc heated with Magnesium oxide

No reaction — Zn is less reactive than Mg.

3. Zinc heated with Copper oxide

Reaction occurs because Zn is more reactive than Cu.

$$Zn+CuO\to ZnO+Cu$$

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4. Magnesium heated with Zinc oxide

Reaction occurs because Mg is more reactive than Zn.

$$Mg+ZnO\to MgO+Zn$$

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5. Magnesium heated with Magnesium oxide

No reaction — metal cannot displace itself.

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6. Magnesium heated with Copper oxide

Reaction occurs because Mg is more reactive than Cu.

$$Mg+CuO\to MgO+Cu$$

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7. Copper heated with any oxide

No reaction — Cu is least reactive, cannot displace any metal.

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Final Result Summary Table

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Therefore, displacement reactions take place in:

✔ Magnesium + Zinc oxide

✔ Magnesium + Copper oxide

✔ Zinc + Copper oxide

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Q2. Which metals do not corrode easily?

Gold, silver and platinum
They are least reactive (do not react with air or moisture).

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Q3. What are alloys?

An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal, made to improve strength, hardness or corrosion resistance.

Examples: Brass (Cu + Zn), Bronze (Cu + Sn), Stainless steel (Fe + Cr + Ni)