Chapter 3 Science Class 10 Metals and Non Metals

Chapter 3 Science Class 10 Metals and Non-Metals

In-text Questions

Page 40

1. Chapter 3 Science Class 10

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 is a metal which is liquid at room temperature.

(ii) Sodium metal can be easily cut with a knife.

(iii) Copper is the best conductor of heat.

(iv) Lead is a poor conductor of heat.

2. Chapter 3 Science Class 10

Explain the meanings of malleable and ductile.

AnswerMalleable metals can be beaten into thin sheets. This property is called malleability and such metals are called malleable. Gold and silver are more malleable metals.

Ductile- The ability of metals to be drawn into thin wires, is called ductility and these metals are called ductile. Gold is the most ductile metal.

Chapter 3 Science Class 10 Page 46

1. Why is sodium kept immersed in kerosene oil?

AnswerSodium reacts vigorously with oxygen and catches fire if kept in open. Hence, to protect it and to prevent accidental fires, they are kept immersed in kerosene oil.

2. Chapter 3 Science Class 10

Write equations for the reactions of

(i) Iron with steam

(ii) Calcium and potassium with water.

Answer

(i) 3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g)

(ii) Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g)

2K(s) + 2H2O(l) → 2KOH(aq) + H2(g) + Heat Energy

3. Chapter 3 Science Class 10

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

Class 10 Science Chapter 3 Question Answer

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.

Answer

(i) Metal B is the most reactive metal because it gives a displacement reaction with Iron (II) Sulphate.

(ii) When metal B is added to a solution of copper (II) sulphate, displacement reaction takes place and as a result of it the blue colour of the solution of copper II sulphate fades away and copper is displaced and get deposited on metal B.

(iii) Metal B is most reactive as it displaces iron from its solution.

Metal A is less reactive because it displaces copper from its solution.

Metal C is even less reactive because it can only displace silver from its solution. Metal D is the least reactive because it cannot displace any metal from its solution. Hence the decreasing order of the reactivity of metals will be as follows- B > A > C > D

4. Chapter 3 Science Class 10

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

Answer- When diluting hydrochloric acid (HCI) is added to a reactive metal, then Hydrogen (H2) gas is liberated.

When iron reacts with dilute H2SO4 the chemical reaction occurs is- Fe(s) + H2SO4(aq) → FeSO4(aq) +H2(g)

5. Chapter 3 Science Class 10

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 in comparison to iron therefore, zinc will replace iron from the solution of iron (II) sulphate, as a result of which the light green colour of iron sulphate solution becomes colourless.

The chemical reaction takes place is- Zn(s) + FeSO4(aq) → ZnSO4(aq) + Fe(s)

Chapter 3 Science Class 10 Page 49

1. Chapter 3 Science Class 10

(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?

Answer

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

NCERT Solutions for Class 10 Science Chapter 3 Q1

(ii) Formation of N2O

Class 10 Science Chapter 3 Question Answer Q1

(iii) Ions present in Na2O

Cation = Na+1 (Sodium cation)

Anion = O-2 (Oxide anion)

Ions Present in MgO

Cation = Mg2+ (Magnesium cation)

Anion = O2- (Oxide anion)

2. Chapter 3 Science Class 10

Why do ionic compounds have high melting points?

Answer- Ionic compounds have a strong interionic attraction force which is called electrostatic force of attraction. Therefore, it requires a lot of energy to break these forces. That is why ionic compounds have high melting points.

Chapter 3 Science Class 10 Page 53

1. Define the following terms-

(i) Mineral

(ii) Ore

(iii) Gangue.

Answer

(i) Mineral- The elements or compounds, which found naturally in the Earth’s crust are called minerals.

(ii) Ore- At some places, minerals contain a very high percentage of a particular metal and the metal can be profitably extracted from it. These minerals are called ores. Example, Cinnabar [HgS] is an ore of mercury.

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

2. Chapter 3 Science Class 10

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

Answer- Gold and platinum metals are found in nature in the free state.

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

Answer- The chemical process used for obtaining a metal from its oxide is reduction. For this carbon and active metals like Al are used as reducing agents.

Page 55

1. Chapter 3 Science Class 10

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

Class 10 Science Chapter 3 Solutions

In which cases will you find displacement reactions taking place?

Answer- A metal with higher reactivity will displace metal of lower reactivity from their compound. Among zinc, magnesium, and copper, magnesium is most reactive whereas copper is the least reactive. Therefore, in the following situation, displacement reaction will be as-

Class 10 Chapter 3 Science

2. Chapter 3 Science Class 10

Which metals do not corrode easily?

Answer- The unreactive metals which do not react with air, water, and acids do not corrode easily. Example- Gold and Platinum.

Read Also

NCERT Class 10th Science Chapter 1

NCERT Class 10th Science Chapter 2

3. Chapter 3 Science Class 10

What are alloys?

Answer- A homogeneous mixture of two or more metals or a metal and a non-metal is called an alloy. Alloy is prepared by first melting the primary metal and then, dissolving the other elements in indefinite proportions. It is then cooled to room temperature. Example- Steel is an alloy of iron and carbon.

Textbook Questions

1. Chapter 3 Science Class 10

Which of the following pairs will give displacement reactions?

(a) NaCl solution and copper metal

(b) MgCl2 solution and aluminum metal

(c) FeSO4 solution and copper metal

(d) AgNO3 solution and copper metal.

Answer- (d) AgNO3 solution and copper metal.

2. Chapter 3 Science Class 10

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.

Answer- (C) Applying a coating of zinc.

3. Chapter 3 Science Class 10

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

Answer- (a) calcium.

4. Chapter 3 Science Class 10

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

Answer- (c) Zinc is more reactive than tin.

NCERT Solutions for Class 10 Science Chapter 3

5. Chapter 3 Science Class 10

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.

Answer- (a) (i) If the given sample is broken into pieces on beating with hammer then it is non-metal but if it is converted into thin sheet then it is metal because metals are malleable.

(ii) A circuit is prepared by connecting given apparatus (battery, bulb, wire and switch) and the given sample is inserted between two terminals, if bulb will glow when switch is on then the sample is metal because metals are good conductor of electricity. If the bulb will not glow then sample is non-metal.

(b) (i) Metals are malleable therefore, they can be beaten up into thin sheets and can be used in making different types of utensils, containers and other items whereas this cannot be done in non-metals.

(ii) Metals are good conductors of electricity therefore, it is used in making electric circuit wires, whereas not from non-metals.

6. Chapter 3 Science Class 10

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

Answer- Oxides that behave as both acidic and basic oxides means they react with acid and base both and forms salt and water are called amphoteric oxides.

Example- Aluminium oxide (Al2O3), Zinc oxide (ZnO).

Aluminum oxide reacts with acid and base in the following manner- Al2O3 + 6HCI → 2AICI3 + 3H2O

Al2O3 + 2NaOH → 2NaAIO2 + H2O

7. Chapter 3 Science Class 10

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

Answer- Metals that are more reactive than hydrogen and displace it from dilute acids are Magnesium and Zinc.

Metals that are less reactive than hydrogen and do not displace it from dilute acids are copper and silver.

8. Chapter 3 Science Class 10

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, cathode, and electrolyte is taken as-

Anode → Impure metal

Cathode → Thin strip of pure metal

Electrolyte → Solution of salt of the metal

Example- CuSO4 solution is used in the purification of copper.

9. Chapter 3 Science Class 10

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 below:

Metals and Non Metals

Collection of Gas

(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.

Answer- When sulphur powder is heated in the air then sulphur dioxide gas is formed.

(a) (i) There will be no action of gas evolved (SO2) on dry litmus paper.

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

(b) Balanced chemical equation for the reaction taking place.

S(s) + O2(g) → SO2 (g)

SO2(g) + H2O(l) → H2SO3(aq)

10. Chapter 3 Science Class 10

State two ways to prevent the rusting of iron.

Answer- Two ways to prevent the rusting of iron are as follows-

(i) By applying oil, grease, or paint on the surface of the iron.

(ii) Galvanisation- Surface of iron is coated with a layer of zinc metal.

11. Chapter 3 Science Class 10

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

Answer- Non-metals combine with oxygen and forms two types of oxides-Acidic and Neutral.

For Example- N2O5 or N2O3 is an acidic oxide whereas CO is a neutral oxide.

12. Chapter 3 Science Class 10

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.

Answer- (a) Platinum, gold, and silver are on the lower side of the reactivity series mean reactivity of these is very less. So they do not react easily with oxygen and moisture present in atmosphere and also with acids. These metals do not corrode easily so lusture is maintained. These metals are malleable and ductile. Due to these reasons platinum, gold and silver are used to make jewellery.

(b) Sodium, potassium, and lithium are very reactive metals and react vigorously with air as well as moisture present in the atmosphere and forms oxide and hydroxide. So if these are kept open, they catch fire. Therefore, they are stored under kerosene oil in order to prevent their contact with air and moisture. Hence these are safe and accidental fire is controlled.

(c) Aluminium is a highly reactive metal SO at ordinary temperature, it reacts with oxygen present in air to form a thin layer of aluminium oxide. This layer prevent the aluminium from further oxidation, and corrosion. Aluminium is a good conductor of heat so it is also 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 carbonate and sulphide.

13. Chapter 3 Science Class 10

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- Copper reacts with moist carbon dioxide in the air to form basic copper carbonate and due to which copper vessel becomes tarnished. The acid present in the lemon or tamarind reacts with basic copper carbonate and dissolves the layer. That is why tarnished copper vessels are cleaned with lemon or tamarind juice.

14. Chapter 3 Science Class 10

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

Answer- These are the differences between metal and non-metals on the basis of their chemical properties.

  1. Metals are electropositive so they lose electrons easily and form cations while non-metals are electronegative so they gain electrons and form anions.
  2. Metals forms basic oxides by oxidation in air white non-metals forms acidic and neutral oxides.
  3. Metal oxides form Alkali by the reaction with water and salt with acids while non-metal oxides form acid by the reaction with water and salt with Alkali.
  4. Metals forms oxide and H2 by the reaction with water also while non-metals do not so.
  5. Metals form salt and H2 by the reaction with dilute hydrogen acids while non-metals do not react with dilute hydrogen acids.

Class 10 Science Chapter 3 Question Answer

15. A man went door to door posing as a goldsmith. He promised to bring back the gliter 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?

Answer- The man must have dipped the gold bangles in the solution of aqua regia, a 3 : 1 mixture of concentrated HCl and concentrated HNO3. Gold is soluble in aqua regia.

After dipping the gold bangles in aqua regia the outer layer of gold gets dissolved and the inner shiny layer appears. That is why the weight of gold bangles reduced.

16. Class 10 Science Chapter 3 Question Answer

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

Answer- The reactivity of copper metal is very low so it does not react with hot water and steam. Opposite to this iron present in steel reacts with steam so steel corrodes. So, copper is used to making hot water tanks and not steel.

Summary

(1) Elements can be classified as metals or non-metals on the basis of their properties.

(2) Metals are ductile, malleable, lustrous and are good conductors of heat and electricity. Metals are sonorous also.

(3) Metals are solids at room temperature, except mercury which is liquid at room temperature.

(4) Metals are generally hard but sodium, potassium, etc. metals are soft.

(5) Metallic lustre- Metals, in their pure state, have a shining surface. This property is called metallic luster.

(6) Malleability- Metals can be beaten into thin sheets. This property is called malleability.

(7) Ductility- The ability of metals to be drawn into thin wires is called ductility.

8) The malleability of gold and silver is maximum and gold is most ductile metal.

(9) Silver and copper are good conductors of heat while lead and mercury are bad conductors of heat.

(10) Metals are electropositive element because they form positive ions by losing electrons to non-metals.

Class 10 Science Chapter 3 Solutions

(11) Alkali metals like lithium, sodium, potassium, are so soft that they can be cut with a knife.

(12) Non-metals have properties opposite to that of metals. They are neither malleable nor ductile.

(13) Non-metals are bad conductors of heat and electricity, except graphite, which conducts electricity.

(14) Non-metals are electronegative elements because they form negatively charged ions by gaining electrons by the reaction with metals.

(15) The numbers of non-metals are less than metals.

(16) Non-metals are generally solid or gas while bromine is a non-metal which is liquid.

(17) The melting points and boiling points of metals are high but the melting points of Galium and Caesium are very low.

(18) Iodine is lustrous although it is non-metal.

(19) Allotropes- Different forms of an element having different properties are called Allotropes. Example- Graphite and Diamond are allotropes of carbon.

Class 10 Science Chapter 3 Solutions

(20) Metals combine with oxygen to form basic oxides but aluminum oxide and zinc oxide show the properties of both basic as well as acidic oxides so these oxides are known as amphoteric oxides.

(21) Most metal oxides are insoluble in water but some of these dissolve in water to form alkalis, e.g., Sodium oxide.

(22) Non-metals form oxides which are either acidic or neutral.

(23) At normal temperature a layer of oxide is formed on the surface of metals like Mg, Al, Zn and Pb which protects these metals from further oxidation.

(24) Anodising is a process of forming a thick oxide layer of aluminum.

(25) Different metals have different reactivities with water and dilute acids.

(26) Reactivity Series is a list of metals arranged in order of their decreasing activities.

(27) Metals above hydrogen in the reactivity series can displace hydrogen from dilute acids.

(28) Non-metals do not displace hydrogen from dilute acids. They react with hydrogen to form hydrides.

(29) A more reactive metal displaces a less reactive metal from its salt solution.

Class 10 Science Chapter 3 Solutions

(30) H2 gas is not liberated when metals react with Nitric acid (HNO3) because HNO3 is a strong oxidising agent, it oxidises the H2 produced to water and itself gets reduced to any of the nitrogen oxides.

(31) The compound formed by the transfer of electrons from a metal to a non-metal are known as ionic compounds or electrovalent compounds.

(32) Ionic compounds are solid, hard and brittle. Melting points and boiling points of these are high.

(33) Ionic compounds are soluble in water but insoluble in solvents like kerosene, petrol, etc.

(34) Ionic compounds conduct electricity in solution and molten states.

(35) Metals are found in nature as free states or in the form of their compounds.

(36) Mineral- The elements or compounds, which found naturally in the earth’s crust are called minerals.

(37) Ore- The mineral which contain a very high percentage of a particular metal and extraction of metal is convenient and economically profitable is called ores.

(38) Metallurgy- The extraction of metals from their ores and then refining them for use is known as metallurgy.

(39) Gold, Silver, Platinum, and Copper are found in a free state.

Class 10 Chapter 3 Science

(40) Ores mined from the earth are usually contaminated with large amounts of impurities such as soil, sand, etc., called gangue.

(41) Enrichment of Ore- The removal of sand, gravel, etc. (Gaunge) from ore is called enrichment of ores.

(42) Calcination- The process of heating the carbonate and Hydrated oxide ore in presence of limited air to convert it into oxide is called calcination.

(43) Roasting- The process of heating the sulphide ore in presence of excess air at high temperature to convert it into oxide is called roasting.

(44) Most common method used for the purification of metals is electrolytic refining.

(45) Alloy- A homogeneous mixture of two or more metals or a metal and a non-metal is called alloy.

(46) Corrosion- The surface of some metals, such as iron, is corroded when they are exposed to moist air for a long period of time. This process is called corrosion.

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