NCERT Chapter 3 Science Class 10 Additional question solution || Metals and Non metals Solution|| Chemistry || Science ||

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                                 Page: 40

 Ques 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 1: (i) Metal that exists in liquid state at room temperature are→ Mercury (because it's melting point is very low). 

(ii) Metals that can be easily cut with a knife are→ Sodium, Potassium (because it is very soft). 

(iii) Metal that are the best conductors of heat are→ Silver, Gold .

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

Ques 2: Explain the meanings of malleable and ductile. 

Ans 2: Malleable: Substances that can be easily converted into thin sheets by beating are called malleable.  Most of the metals are malleable. Gold and Silver are most malleable metals. 

Ductile: Substances that can be easily drawn into thin wires are called ductile. Most of the metals  are ductile. Gold is the most ductile metal.

                              Page: 46

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

Ans 1: Metals such as potassium(K) and sodium(Na) react so vigorously with oxygen that they catch fire if kept in the open. Hence, to protect them and to prevent accidental fires, they are  kept immersed in kerosene oil. 

Ques 2: Write equations for the reactions of 

(i) iron with steam

(ii) calcium and potassium with water

Ans 2: (i) Iron react with steam to form the metal oxide and hydrogen. 

          3Fe(s) + 4H2O(g) → Fe 3 O 4 + 4H2

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

           C a + 2H2O(l) → C a(OH)2 + H2

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 + 2H2O → 2KOH + H2 + 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. (For table refer to your N C E R T book). 

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 (I I) sulphate?

(iii) Arrange the metals A, B, C and D in the order of decreasing reactivity. 

Ans 3: (i) As per reactivity series, Iron is most reactive metal among Iron(Fe), Silver(A g) and Copper(Cu) and copper is the least reactive. Since B can displace Iron from its sulphate, so B is the most reactive metal. 

(ii) As B is more reactive than Iron. So, it will displace Copper from its Copper Sulphate solution. 

(iii) B is most reactive and D is the least reactive metal as  unable to displace any of the solutions. Copper is more reactive than Silver and metal A can displace Copper, so A is more reactive than C. 

Hence, the order of decreasing reactivity is B > A > C > 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 Sulphuric acid (H2 SO 4).

Ans 4: When reactive metals react with dilute hydrochloric acids, gives a salt and hydrogen gas 

Metal + Dilute acid → Salt + Hydrogen

Reaction between Iron and H2 SO 4:

           Fe + H2 SO 4 → Fe SO 4+ H2

Ques 5: What would you observe when zinc is added to a solution of iron (I I) sulphate?

Write the chemical reaction that takes place.

Ans 5: Zinc is more reactive than Iron. When Zinc is added to Iron (I I) Sulphate, Zinc

displaces Iron from its solutions and Zinc sulphate is formed.

             Z n + Fe SO 4  → Z n SO 4 + Cu 

                                 Page: 49

Ques 1: (i) Write the electron-dot structures for sodium, oxygen and magnesium. 

(ii) Show the formation of Na 2 O and Mg O by the transfer of electrons.

(iii) What are the ions present in these compounds?

Ans 1: (i) Electron – dot structure for Sodium:

Electron – dot structure for Oxygen:

Electron – dot structure for Magnesium:



(ii). Formation of Na 2 O by transfer of electron:
Formation of Mg O by transfer of electron:

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

Ans 2: Ionic compounds have higher melting and boiling points. Because ionic compounds  
are formed by the attraction force of two opposite ions and a considerable amount 
of energy is required to break this strong inter-ionic attraction. 
                                Page: 53

Ques 1: Define the following terms. 

(i) Mineral

(ii) Ore

(iii) Gangue.

Ans 1:

(i) Mineral: The elements or compounds, which occur naturally in the earth’s crust, are known  as minerals. 

(ii) Ore: If minerals contain a very high percentage of a particular metal and the metal can be profitably extracted from it. These minerals are called ores. 

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

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

Ans 2: The metals which are the least reactive, they are often found in a free state.  

For example: Gold, silver, platinum and copper are found in the free state.

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

Ans 3: Metals low in the reactivity series are very unreactive. The oxides of these  metals can be reduced to metals by heating alone.  

                 2HgO → 2Hg + O

The metals in the middle of the activity series such as iron, zinc, lead, copper, etc., are moderately reactive. These metal oxides are reduced to the corresponding metals by using suitable reducing agents 

Z n O(s) + C(s) → Z n(s) + CO(g)

The metals high up in the reactivity series are very reactive. They are separated from their oxides by electrolysis process.

                                   Page: 55

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

Ans 1: Magnesium is the most reactive among these three metals and Zinc is more reactive than Copper. So, Magnesium will displace Zinc oxide and Copper oxide whereas Zinc will displace Copper oxide only.

Ques 2: Which metals do not corrode easily? 

Ans 2: The metals which are the least reactive, do not corrode easily. 

For example: Gold, silver, platinum and copper.

Question 3:

What are alloys?

Ans 3: An alloy is a homogeneous mixture of two or more metals, or a metal and a non- metal. 

For example:

» Stainless steel is an alloy of Nickel and Chromium.

» Amalgam is an alloy of Mercury.

» Brass is an alloy of Copper and Zinc.

» Bronze is an alloy of Copper and Tin.

» Solder is an alloy of Lead and Tin.

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