NCERT Solutions for Class 10th Science
Chapter 3 – METALS AND NON-METALS
(Complete Downloadable Chapter Solution PDF file is at the bottom of the page)
Q.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.
Ans (i) Mercury
(ii) Sodium
(iii) Silver
(iv) Lead
Q.2 Explain the meanings of malleable and ductile.
Ans Malleable: Substances which can be beaten into thin sheets are called malleable. Most of the metals are malleable like gold, silver etc.
Ductile: Substances which can be drawn into thin wires are called ductile. Most of the metals are ductile like gold, silver etc.
Q.3 Why is sodium kept immersed in kerosene oil?
Ans Sodium is a very reactive metal and reacts vigorously with water and oxygen (air) and even catches fire (due to highly exothermic reaction). Hence to protect it and to prevent accidental fires, it is kept immersed in kerosene oil.
Q.4 Write equations for the reactions of
(i) iron with steam
(ii) calcium and potassium with water
Q.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
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.
Q.6 Which gas is produced when dilute hydrochloric acid is added to a reactive metal? Write the chemical reaction when iron reacts with dilute H2SO4.
Q.7 What would you observe when zinc is added to a solution of iron(II) sulphate? Write the chemical reaction that takes place.
Q.8 (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?
Q.9 Why do ionic compounds have high melting points?
Ans Ionic compounds have a strong inter-ionic attraction between cations and anions which requires a considerable amount of energy to break. Hence ionic compounds have high melting points.
Q.10 Define the following terms.
(i) Mineral (ii) Ore (iii) Gangue
Ans (i) Mineral: The elements or compounds, which occur naturally in the earth’s crust, are known as minerals. For example borax, bismuth etc.
(ii) Ore: Ores are the minerals which contain a very high percentage of a particular metal and the metal can be profitably extracted from them. For example haematite (Fe2O3) is an ore of iron, cinnabar (HgS) is an ore of mercury etc.
(iii) Gangue: The impurities such as soil, sand, etc. present in ores are known as gangue.
Q.11 Name two metals which are found in nature in the free state.
Q.12 What chemical process is used for obtaining a metal from its oxide?
Q.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?
Q.14 Which metals do not corrode easily?
Ans Metals which are least reactive do not corrode easily. For example gold, silver, platinum etc.
Q.15 What are alloys?
Ans An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal. For example brass is an alloy of copper and zinc, bronze is an alloy of copper and tin etc.
EXERCISES
Q.1 Which of the following pairs 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.
Ans (d) AgNO3 solution and copper metal
This is because copper (Cu) is more reactive than silver (Ag)
Q.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.
Ans (c) Applying a coating of zinc
Q.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.
Ans (a) calcium
Q.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.
Ans (c) zinc is more reactive than tin.
Q.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.
Q.6 What are amphoteric oxides? Give two examples of amphoteric oxides.
Q.7 Name two metals which will displace hydrogen from dilute acids, and two metals which will not.
Q.8 In the electrolytic refining of a metal M, what would you take as the anode, the cathode and the electrolyte?
Q.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.
Q.10 State two ways to prevent the rusting of iron.
Q.11 What type of oxides are formed when non-metals combine with oxygen?
Q.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.
Q.13 You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice.
Q.14 Differentiate between metal and non-metal on the basis of their chemical properties.
Q.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 The solution used by goldsmith is aqua-regia.
Aqua regia is a freshly prepared mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio of 3:1 by volume. It dissolved the outer layer of gold due to which the shiny inner layer appears. This is the reason that the gold bangles sparkled like new but their weight was reduced drastically.
Q.16 Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron).
Ans Copper is used to make hot water tanks and not steel because copper does not react with water whereas iron reacts with steam to produce iron oxide and hydrogen. Moreover, copper is better conductor of heat than steel and results in lower heat losses.