NCERT Solutions for Class 10 Science Chapter 3 Metals and Non-metals

NCERT Solutions for Class 10 Science Chapter 3 Metals and Non-metals

Chapter 3 Metals and Non-metals NCERT Solutions for Class 10 Science is present here that are curated by our expert teachers who have vast experience of teaching students. It will make learning and understanding more easier with detailed and accurate NCERT Solutions. You can access Class 10 Science NCERT Solutions anywhere without any difficulty and understand the answers at your own comforts.

NCERT Solutions for Class 10 Science Chapter 3 Metals and Non-metals

Chapter 3 Metals and Non-metals Class 10 Science NCERT Solutions


NCERT In Text Questions

Page No: 40

1. Give an example of a metal which

(i) is a liquid at room temperature.

Solution

Mercury

(ii) can be easily cut with a knife.

Solution

Sodium

(iii) is the best conductor of heat.

Solution

Silver

(iv) is a poor conductor of heat.

Solution

Mercury and Lead

2. Explain the meanings of malleable and ductile.

Solution

Malleable: A material which can be turned into thin sheets on hammering, is said to be malleable.
Ductile: A material which can be turned into thin wires by stretching, is said to be ductile.

Page No: 46

1. Why is sodium kept immersed in kerosene oil?

Solution

Sodium is a very reactive metal so it reacts vigorously with the oxygen of air and catches fire. It is kept immersed in kerosene oil to protect it from the action of oxygen, moisture and carbon dioxide of air and to prevent accidental fires.

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

Solution


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.

Metal
Iron (II) sulphate
Cooper (II) sulphate
Zinc sulphate
Silver nitrate
A.
No reaction
Displacement
B.
Displacement
No reaction
C.
No reaction
No reaction
No reaction
Displacement
D.
No reaction
No reaction
No reaction
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 most reactive metal.
(ii) B will displace copper from copper sulphate.
(iii) Arrangement of metals in the order of decreasing reactivity B>A>C>D.

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 a metal reacts with dilute hydrochloric acid, the gas produced is hydrogen (H2). Iron and dilute H2SO4 react to produce H2, as under the given reaction:
Fe (s) + H2SO4 (aq) → FeSO4 (aq) + H2 (g)

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

Solution

When zinc is added to the solution of iron sulphate, the colour of iron sulphate solution changes because zinc is more reactive than iron, therefore, it displaces iron from its solution of iron sulphate and a grey precipitate of iron and a colourless/white solution of zinc sulphate is formed.
Zn (s) + FeSO4 (aq) → ZnSO4 (aq) + Fe (s)

Page No: 49

1. (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?

Solution

(i) The representation of elements with valence electrons as dots around the elements is referred to as electron-dot structure for elements.
(ii) 

(iii) The ions present in Na2O are Na+ and O2- ions and in MgO are Mg2+ and O2- ions.

2. Why do ionic compounds have high melting points?

Solution

Ionic compounds have strong force of electrostatic attraction between the oppositely charged ions of an ionic compound, so a lot of heat energy is required to break this force of attraction and melt the ionic compound. Due to this, ionic compounds have high melting points.

Page No: 53

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

Solution

(i) Minerals: The elements or compounds, which occur naturally in earth’s crust, are known as minerals.
(ii) Ores: Those minerals from which contains metals can be extracted profitably are known as ores.
(iii) Gangue: The unwanted rocky, earthy or sandy materials which are associated with ores as impurities are called gangue.

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

Solution

The metals at the bottom of the reactivity series are mostly found in free state. Gold (Au) and Platinum (Pt) are two metals that are found in the free state.

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

Solution

The chemical process used for obtaining a metal from its oxide is reduction. In this process, metal oxides are reduced by using suitable reducing agents such as carbon or by highly reactive metals to displace the metals from their oxides.
For example, zinc oxide is reduced to metallic zinc by heating with carbon.

Page No: 55

1. 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

2. Which metals do not corrode easily?

Solution

Those metals which are at the bottom of the reactivity series' are highly unreactive and do not corrode easily.

3. What are alloys?

Solution

Alloys are homogeneous mixtures of more than one metal or even metals and non-metals. An example of alloy is brass which is made up of copper and zinc.

Page No: 56

Exercises

1. Which of the following pairs will give displacement reactions?
(a) NaCl solution and copper metal
(b) MgCl2solution and aluminium metal
(c) FeSO4solution and silver metal
(d) AgNO3solution and copper metal.


Solution

(d) AgNO3solution and copper metal.

2. 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.


Solution

(c) Applying a coating 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

(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

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

Solution

(a) With the hammer, we can beat the sample and if it can be beaten into thin sheets, then it is a metal otherwise a non-metal. Similarly, we can use the battery, bulb, wires, and a switch to set up a circuit with the sample. If the sample conducts electricity, then it is a metal otherwise a non-metal.

(b) The above tests are useful in distinguishing between metals and non metals as these are based on the physical properties. No chemical reactions are involved in these tests.

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

Solution

Those oxides which can act as both acidic and basic oxides are known asamphoteric oxides.
Examples: aluminium oxide (Al2O3), zinc oxide (ZnO).

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

Solution

Sodium and calcium can displace hydrogen from dilute acids as they lie above hydrogen in the reactivity series and are more reactive than hydrogen. Copper and silver can not displace hydrogen from dilute acids as they lie below hydrogen in the reactivity series and are less reactive than hydrogen.

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

Answer

In the electrolytic refining of a metal M:
Anode → Impure metal M
Cathode → Thin strip of pure metal M
Electrolyte → Solution of salt of the metal M.

9. 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.

Solution

(a) Sulphur is a non-metal, on burning it will be converted into its oxide. Oxides of non-metals are acidic. Therefore in this case, sulphur dioxide produced will be acidic.
(i) There will be no action of the gas on dry litmus paper.
(ii) Wet litmus paper will turn to red.

(b) S (s) + O2(g) → SO2 (g)

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

Solution

Two ways to prevent the rusting of iron are:
(i) Oiling, greasing, or painting: By applying oil, grease, or paint, the surface becomes water proof and the moisture and oxygen present in the air cannot come into direct contact with iron. Hence, rusting is prevented.
(ii) Galvanisation: An iron article is coated with a layer of zinc metal, which prevents the iron to come in contact with oxygen and moisture. Hence, rusting is prevented.

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

Solution

When non-metals combine with oxygen the oxides formed are either acidic or neutral. Examples of acidic oxides are NO2, SO2 and examples of neutral oxides are NO, CO etc.

12. 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.

Solution

(a) Platinum, gold and silver are used to make jewellery because they are very lustrous. Also, they are very less reactive and do not corrode easily.

(b) Sodium, potassium and lithium react with water or moisture in air producing a lot of heat along with evolution of hydrogen. As a result the hydrogen gas evolved, catches fire. To avoid contact with air and water, these metals are not kept in air but are kept under kerosene oil.

(c) Though aluminum is a highly reactive metal, it is resistant to corrosion. This is because aluminium reacts with oxygen present in air to form a thin layer of aluminium oxide. This oxide layer is very stable and prevents further reaction of aluminium with oxygen. Also, it is light in weight and a good conductor of heat. Hence, it is used to make utensils for cooking.

(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction because metals can be easily extracted from their oxides rather than from their carbonates and sulphides since oxides are easier to reduce than sulphides and carbonates.

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

Copper reacts with moist carbon dioxide in air to form copper carbonate and as a result, copper vessel loses its shiny brown surface forming a green layer of copper carbonate. The citric acid present in the lemon or tamarind neutralises the basic copper carbonate and dissolves the layer. That is the reason why tarnished copper vessels are cleaned with lemon or tamarind juice to give the surface of the copper vessel its characteristic lustre.

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

Solution

Metal
Non-metal
Metals are electropositive.Non-metals are electronegative.
Metals form basic oxides.Non-metals form acidic oxides or netural oxides.
Metals displace hydrogen from dilute acids.They can't replace hydrogen from dilute acids.
Metals form ionic chlorides with chlorine. These ionic chlorides are electrolytes but non-volatile.Non-metals form covalent chlorides with chlorine (which are non-electrolytes but volatile).
They react with water to form oxides and hydroxides. Some metals react with cold water, some with hot water, and some with steam.Non-metals react with hydrogen to form stable, covalent hydrides.

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 man has used an aqua-regia solution (mixture of conc. HCl and conc. HNO, in the ratio of 3 : 1 by volume). It is capable of dissolving metals like Gold and Platinum. Since, the dull layer of gold was removed from its surface so there was original shine on the bangles.

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

Solution

Copper is used to make hot water tanks and not steel because the iron (in steel) is more reactive than copper, it react with hot steam to produce ferrosoferric oxide. Due to which the body of tank will become weaker and weaker. On other hand, copper does not react with hot water.
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