Lesson: Metals and Non-metals

Question 1

Give an example of a metal which

(a) is a liquid at room temperature.

(b) can be easily cut with a knife.

(d) is a poor conductor of heat.

Solution:

(a) Mercury

(b) Sodium

(d) Mercury and lead

Question 2

Explain the meanings of malleable and ductile.

Solution:

A substance is said to be malleable if it can be beaten into thin sheets.

A substance is said to be ductile if it can be drawn into thin wires.

Generally metals are both ductile and malleable.

Question 3

Why sodium is kept immersed in kerosene oil?

Solution:

Sodium is a highly reactive element. It is kept immersed in kerosene oil to avoid its reaction with oxygen. Such reactions are also explosive in nature.

Keeping sodium immersed in kerosene helps:

a) preventing accidental damage.

b) storing sodium in its pure form.

Question 4

Write equations for the reactions of:

(i) Iron with steam

(ii) Calcium and potassium with water

Solution:

(i) $3 F e (s) + 4 H_{2} O (g) \to F e_{3} O_{4} (a q) + 4 H_{2} (g)$

(ii) $C a (s) + 2 H_{2} O (l) \to C a {(O H)}_{2} (a q) + H_{2} (g) + H e a t$

$2 K (s) + 2 H_{2} O (l) \to 2 K O H (a q) + H_{2} (g) + H e a t$

Question 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.

Metal

Iron (II) Sulphate

Copper (II) Sulphate

Zinc Sulphate

Silver nitrate

No reaction

Displacement

No reaction

Displacement

No reaction

Displacement

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.

Solution:

(i) B is the most reactive metal.

(ii) B will displace copper from the copper sulphate solution.

(iii) Arrangement of metals in the order of decreasing reactivity: $B > A > C > D .$

Question 6

Which gas is produced when dilute hydrochloric acid is added to a reactive metal? Write the chemical reaction when iron reacts with dilute $H_{2} S O_{4}$ .

Solution:

When a reactive metal reacts with dilute hydrochloric acid, hydrogen gas is produced.

The chemical reaction when iron reacts with dilute $H_{2} S O_{4}$ is as follows:

$F e (s) + H_{2} S O_{4} (a q) \to F e S O_{4} (a q) + H_{2} (g)$

Question 7

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

Solution:

Zinc is more reactive than iron. So, when it is added to iron(II) sulphate solution, it displaces iron from the solution.

The chemical reaction is as follows:

$Z n (s) + F e S O_{4} (a q) \to Z n S O_{4} (a q) + F e (s)$

Question 8

(i) Write the electron-dot structures for sodium, oxygen and magnesium.

(ii) Show the formation of $N a_{2} O$ and $M g O$ by the transfer of electrons.

(iii) What are the ions present in these compounds?

Solution:

(iii) The ions present in $N a_{2} O a r e N a^{+} a n d O^{2 -} .$

The ions present in $M g O a r e M g^{2 +} a n d O^{2 -} .$

Question 9

Why do ionic compounds have high melting points?

Solution:

The force of attraction in ionic bonds is very strong. Therefore, the ionic compounds require a lot of energy to overcome this bond. That is why ionic compounds have high melting points.

Question 10

Define the following terms.

(i) Mineral

(ii) Ore

(iii) Gangue

Solution:

(i) Mineral are the naturally occurring materials in which metals or their compounds are found on earth.

(ii) Ores are the minerals from which metals can be extracted profitably.

(iii) Gangues are the impurities present in an ore.

Question 11

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

Solution:

Silver and gold

Question 12

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

Solution:

A metal can be obtained from its oxide by the process of reduction.

Question 13

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?

Solution:

Metal	Zinc	Magnesium	Copper
Zinc oxide	No reaction	Displacement	No reaction
Magnesium oxide	No reaction	No reaction	No reaction
Copper oxide	Displacement	Displacement	No reaction

Question 14

Which metals do not corrode easily?

Solution:

Metals which are least reactive, such as silver, gold, etc. do not corrode easily.

Question 15

What are alloys?

Solution:

An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal. The properties of an alloy are different from the constituent matters.