Chapter-3 Metals and Non-metals

Question 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) Mercury

(ii) Sodium

(iii) Silver/Copper

(iv) Lead/Mercury

Question 2.

Explain the meaning of malleable and ductile.?

Answer:

  1. Metals which can be beaten into thin sheets are known as malleable. For Example Silver
  2. Metals which can be beaten into thin wires are known as ductile. For Example Gold

Question 3

Why is sodium kept immersed in kerosene oil?

Answer:

Sodium is a very reactive metals. Sodium is immersed in kerosene oil to prevent reaction with oxygen, moisture and carbon dioxide.

Question 4

Write the equations for the reactions of:
(a) iron with steam
(b) calcium until water

Answer:

(a) 3Fe(s) + 4H2O(g) ➝ Fe3O4(s) + 4H2(g)

(b) Ca(s) + 2H2O(7) ➝ Ca(OH)2(aq) + H2(g)

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:

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) sulphate?
  3. Arrange the metals A, B, C and D in the order of decreasing reactivity.

Answer:

(1) Metal ‘B’ is most reactive.

(2) Since ‘B’ is more reactive than iron, it is also more reactive than copper. The blue colour of solution will slowly fade.

(3) The decreasing order of reactivity of metals is: B > A > C > D.

Question 6

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

Answer:

Hydrogen gas is liberated

Fe(s) + H2SO4(aq) → FeSO4(aq) + H2(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.

Answer:

Zinc is more reactive than iron. Zinc displaces Iron from its salt solution. The colour of ferrous sulphate is pale green, which turns colourless.

For example:

FeSO4 + Zn → ZnSO4 + Fe(s)

Question 8

(a) Give electron dot structures for sodium, magnesium and oxygen.
(b) Show the formation of Na2O and MgO by the transfer of electrons.
(c) What are the ions present in these compounds?

Answer:

Question 9

Why do ionic compounds have high melting – points?

Answer:

Ionic charges are those who are having both positive and negative charges. Hence there will be a strong force of attraction between them. Hence it takes a lot of heat to break this force, hence they have strong melting points.

Question 10

Define the following terms:
(a) Minerals
(b) Ores
(c) Gangue

Answer:

(a) Minerals are naturally occurring compounds found in the earth’s crust.

(b) Ores are the minerals from which the metals can be extracted. Ex: Bauxite Al2O3.2H2O is the ore of Al

(c) The impurities associated with the minerals and ores while extracting from the earth are known as Gangue.

Question 11

Name two metals which are formed in nature in free state.

Answer:

Gold and platinum are the metals formed in free state.

Question 12

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

Answer:

Reduction process is used to obtain metal from oxide.

Question 13

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

Answer:

Question 14.

Which metals do not corrode easily?

Answer:

Gold and platinum are the metals which do not corrode easily.

Question 15

What are alloys?

Answer:

Alloys are homogeneous mixture of two or more metals, or even metals and non metals.

Chapter End Questions

Question 16

Which of the following 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) Option D is the correct answer.

Question 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 the above.

Answer:

Answer is (c) Applying a coating of zinc.

Question 18

An element reacts with oxygen to give a compound with high melting point. This compound is also water soluble. The element is likely to be:
(a) Calcium
(b) Carbon
(c) Silicon
(d) Iron

Answer:

Correct answer is Calcium

Question 19

Food cans are coated with tin and not with zinc because
(a) Zinc is costlier than tin
(b) Zinc has higher melting point than tin
(c) Zinc is more reactive than tin
(d) Zinc is less reactive than tin.

Answer:

Zinc is more reactive than tin. Zinc is more electro positive than tin.

Question 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 to distinguish between ,metals and non-metals.

Answer:

(a) Since metals are malleable, With a hammer, convert both the metal and non-metal (solid) into plates. Non-metals having brittle property will crack, when struck with hammer. Now make a cell and switch on the current. If the bulb starts to glow, it means the plates are of metal. If the bulb doesn’t glow it means the plate is a non metal.

(b) These tests are used to demonstrate the malleability and electric conductivity of metals as well as non metals.

Question 21

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

Answer:

The oxides that act both as acid and base and form salt and water are known as amphoteric oxides. Examples:  PbO and Al2O3.

Question 22

Name two metals which can displace hydrogen from dilute acids and two metals which cannot do so.

Answer:

  • Zinc and sodium are the metals which can displace hydrogen from dilute acids
  • Gold and copper can’t displace hydrogen from dilute acids.

Question 23

In the electrolytic refining of metal M, name anode, cathode and electrolyte.

Answer:

Anode:  A Rod of impure metal
Cathode: A Rod of pure metal
Electrolyte: Aqueous solution of soluble salt of metal M.

Question 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 the figure.

What will be the action of gas on
(a) dry litmus paper?
(b) moist litmus paper?
Write a balanced chemical equation for the reaction taking place.

Answer:

(a) The gas is sulphur dioxide (SO2). It will not react with dry litmus paper.

(b) S(s) + O2(g) → SO2(g)

SO2(g) + H2O →H2SO3

Question 25

State two ways to prevent rusting of iron.

Answer:

(1) Rust can be prevented  by using rust proof paints.

(2) Another way to prevent rusting is by galvansing.

Question 26

What types of oxides are formed when non-metals combine with oxygen?

Answer:

The oxides are acidic in nature which means that when they are dissolved in water, their solutions change blue litmus into red.

Question 27

Give reasons for the following:
(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 but still used for making cooking utensils.
(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction.

Answer:

(a)  Platinum, gold and silver are used to make jewellery because they are very less reactive. Because it is not affected by air, moisture or even chemicals.

(b) All these metals readily react with water and produce a lot of heat. So to avoid emitting heat, these are kept under oil.

(c) Aluminium forms a non reactive coating of aluminium oxide. Such a coating helps compounds from reacting with aluminium. Thats why it is used to make utensils.

(d) Because it is a lot easier to extract metals from their oxides than from their carbonates or sulphides, the carbonate and sulphide ores are first transformed to oxides to obtain the metals.

Question 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 sour substances contains acid which dissolves the coating of copper carbonate present on the surface of copper vessel. In return, they get back to there original color. hence they are very effective in cleaning the tarnished vessels.

Question 29

A man went door to door posing as a goldsmith. He promised to bring back the glitter on 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 fraud used the solution aqua regia. Which is concentrated mixture of HCl and nitric acid. Aqua Regia dissolves the upper layer of the dull ornaments which reduces the weight.

Question 30

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

Answer:

It is because the copper never reacts with water or steam whereas iron reacts with steam to corrode the tank.

Question 31

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

Answer:

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