NCERT Solutions For Class 10 Science Chapter 3 Metals and Non Metals

NCERT Books Solutions For Class 10 Science Chapter 3 Metals and Non Metals

NCERT Solutions For Class 10 Science Chapter 3 Metals and Non Metals is the first stepping stone for a student in the competitive world. With the introduction of the CBSE Board Exam for class 10 a few years back, this has become an important gateway for a student as based on the results of class 10th a student selects his future stream of Science, Commerce, or Arts.

Takshila Learning provides you with detailed and well explained NCERT Solutions for Class 10 of each chapter of each subject for NCERT Class 10. These NCERT Solutions help you to easily understand every concept so that you can score high in your CBSE Class 10 Board Exams.

Below you can find the NCERT solution for Class 10th Science. You can get a Solution for the all-important question of “CH 3 Science Class 10 Metals and non metals”

Ques1: Give an example of a metal which-

1. is a liquid at room temperature.
2. can be easily cut with a knife.

• is the best conductor of heat.

1. is a poor conductor of heat.

Ans:      (i) Metal that exists in liquid state at room temperature is Mercury

 

(ii) Metal that can be easily cut with a knife is Sodium

 

(iii) Metal that is the best conductor of heat is Silver

 

(iv) Metals that are poor conductors of heat are Mercury and lead

 

 

Ques 2: Explain the meanings of malleable and ductile.

 

Ans: Substances which can be beaten into thin sheets are called malleable. Substances which can be drawn into thin wires are called ductile. Most of the metals are malleable and ductile.

 

 

 

Pg. No. 46

 

Ques 1: Why sodium is kept immersed in kerosene oil?

Ans: Being highly reactive, Sodium and potassium combine explosively with air as well as water and so catch fire if kept in open. Hence, to prevent accidental fires and accidents, sodium is stored in kerosene oil.

 

 

Ques 2: Write equations for the reactions of:

(i) iron with steam

(ii) calcium and potassium with water

 

Ans:

• Iron react with steam to form the metal oxide and hydrogen.

3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g)

 

• The reaction of calcium with water is exothermic but the heat evolved is not sufficient for the hydrogen to catch fire.

Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g)

Calcium starts floating because the bubbles of hydrogen gas formed stick to the surface of the metal. Potassium react violently with cold water and its reaction is so violent and exothermic that the evolved hydrogen immediately catches fire.

 

2K(s) + 2H2O(l) → 2KOH(aq) + H2(g) + heat energy

 

 

 

Ques 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.

• Which is the most reactive metal?
• What would you observe when metal B is added to a solution of copper (II) Sulphate?
• Arrange the metals A, B, C and D in the order of decreasing reactivity.

 

Ans:

From the given table we can write following observations:

1) A is less reactive than Fe but more reactive than Cu.

2) B is more reactive than Fe but less reactive than Zn.

3) C is more reactive than Ag but less reactive than Fe, Cu and Zn.

4) D is less reactive than Fe, Cu, Zn, Ag.

 

Hence we can conclude that,

(i) B is the most reactive metal.

(ii) B can displace Cu as B is more reactive than Cu.

(iii) The reactivity of these metals in the decreasing order is B > A > C > D.

 

Reactivity series, Zn > B > Fe > A > Cu > C > Ag > D

 

 

Ques 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.

 

Ans: Hydrogen gas is evolved when dilute hydrochloric acid is added to a reactive metal. When iron reacts with dilute H₂SO₄, iron (II) sulphate with the evolution of hydrogen gas is formed.

 

 

 

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

 

Ans:

Zinc is more reactive than iron. So, if zinc is added to a solution of iron (II) sulphate, it would displace iron from the solution.

 

 

 

 

 

Pg No. 49

 

Ques 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?

 

 

 

Ques 2: Why do ionic compounds have high melting points?

 

Ans: Ionic compounds have strong electrostatic forces of attraction between the ions. Hence, it requires a lot of energy to overcome these forces. This is the reason, ionic compounds have high melting points.

 

 

 

 

Pg No. 53

 

Ques 1: Define the following terms:

• Mineral
• Ore
• Gangue

Ans:

(i) Mineral: Most of the elements occur in nature as in combined state as minerals. The chemical composition of minerals is fixed.

 

(ii) Ore: Minerals from which metals can be extracted profitably are known as ores.

 

(iii) Gangue: The impurities (sand, silt, soil, gravel, etc.) present in the ore are called gangue.

 

 

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

Ans: The metals at the bottom of the reactivity series are mostly found in free state. For example: gold, silver, and platinum.

 

 

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

Ans: 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.

 

ZnO + C -> Zn + CO

 

Manganese dioxide is reduced to manganese by treating it with aluminium powder. In this case, aluminium displaces manganese from its oxide.

 

3MnO2(s) + 4Al(s) → 3Mn(l) + 2Al2O3(s) + heat

 

Oxides of more reactive metals are reduced by electrolysis.

 

 

 

 

Pg No. 55

 

Ques 1: Metallic oxides of zinc, magnesium and copper were heated with the following metals.

 

Ans:

 

 

 

Ques 2: Which metals do not corrode easily?

Ans: More reactive a metal is, it can be corroded easily. Less reactive metals are less likely to get corroded. Gold plating provides high resistance to corrosion.

 

 

 

Ques 3: What are alloys?

Ans: Alloys are homogeneous mixtures of two or more elements. The elements could be two metals, or a metal and a non-metal. For example, steel is an alloy of iron and carbon.

 

 

 

EXERCISE

 

Q1. Which of the following pairs will give displacement reactions?

1. NaCl solution and copper metal
2. MgCl2 solution and aluminum metal
3. FeSO4 solution and silver metal
4. AgNO3 solution and copper metal.

 

Ans: (d) AgNO3 solution and copper metal

 

 

 

Ques 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.

 

Ans: (c) Applying a coating of zinc

 

 

 

Ques 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

• calcium
• carbon
• silicon
• iron

 

Ans: (a) The element is likely to be calcium.

 

 

 

Ques 4: Food cans are coated with tin and not with zinc because

• zinc is costlier than tin.
• zinc has a higher melting point than tin.
• zinc is more reactive than tin.
• zinc is less reactive than tin.

 

Ans: (c) Food cans are coated with tin and not with zinc because zinc is more reactive than tin.

 

 

 

Ques 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.

Ans:

(a) If we can beat a sample with the hammer and if it can be beaten into thin sheets (that is, it is malleable), 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 and 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.

 

 

 

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

 

Ans: Those oxides that behave as both acidic and basic oxides are called amphoteric oxides.

Examples: aluminum oxide (Al2O3), zinc oxide (ZnO)

 

 

 

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

Ans: Metals which are more reactive than hydrogen can displace it from dilute acids.

For example: sodium and potassium.

Metals which are less reactive than hydrogen can not displace it.

For example: copper and silver.

 

 

 

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

Ans: 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

 

 

Ques 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.

 

Ans: (a)

(i) There will be no action on dry litmus paper.

 

(ii) Since the gas is sulphur dioxide (SO2), it turns moist blue litmus paper to red because sulphur dioxide reacts with moisture to form sulphurous acid.

 

(b) (i) S + O₂ → SO₂

      (ii) SO₂ + H₂O → H₂SO₃

 

 

 

Ques 10: State two ways to prevent the rusting of iron

Ans: 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) Galvanization: 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.

 

 

 

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

Ans: Non-metals combine with oxygen to form acidic oxides. For example:

 

S + O₂ → SO₂

 

 

 

Ques 12: Give reasons

• Platinum, gold and silver are used to make jewellery.
• Sodium, potassium and lithium are stored under oil.
• Aluminum is a highly reactive metal, yet it is used to make utensils for cooking.
• Carbonate and sulphide ores are usually converted into oxides during the process of extraction.

 

Ans:

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

 

(b) Sodium, potassium, and lithium are very reactive metals and so, react very vigorously with air and water. Hence, they are kept immersed in kerosene oil in order to prevent their contact with air and moisture.

 

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

 

(d) Carbonate and Sulphide ores are usually converted into oxides during the process of extraction as metals can be easily extracted from their oxides rather than from their carbonates and sulphides.

 

 

 

Ques 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.

 

Ans: Copper responds with carbon dioxide in air to form copper carbonate and subsequently, copper vessel loses its gleaming dark coloured surface shaping a green layer of copper carbonate. The citrus extract present in the lemon or tamarind kills the premise copper carbonate and disintegrates the layer. That is the reason, discolored copper vessels are cleaned with lemon or tamarind juice to give the outside of the copper vessel its trademark radiance.

 

 

 

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

 

Metals	Non-metals
1. Metals loose electrons to form positive ions.	Non-metals gain electrons to form negative -ions.
2. Metals form basic oxides.	Nonmetals form acidic oxides.
3. Metals scan displace hydrogen from acids.	Non-metals cannot displace hydrogen from acids.
4. All metals do not combine with hydrogen to form hydrides (except reactive metals like Na, K, Ca).	All non-metals combine with hydrogen to form hydrides.

Ans:

 

 

 

 

Ques 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?

Ans: He must have dipped the gold metal in the solution of aqua regia − a 3:1 mixture of conc. HCl and conc. HNO3. Aqua regia is a fuming, highly corrosive liquid. It dissolves gold in it. After dipping the gold ornaments in aqua regia, the outer layer of gold gets dissolved and the inner shiny layer appears. That is why the weight of gold ornament reduced.

 

 

 

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

Ans: Copper does not react with cold water, hot water, or steam. However, iron reacts with steam. If the hot water tanks are made of steel (an alloy of iron), then iron would react vigorously with the steam formed from hot water.

So, copper is used to make hot water tanks, and not steel.

 

 

 

 

 

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