Metals And Non- Metals (Question Answer) 

QUESTIONS 

 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. 

Answer: (i) A metal liquid at room temperature is Mercury.

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

                (iii) Metal which is best conductor of heat is Copper.

                (iv) Metal which is poor conductor of heat is Mercury.

2. Explain the meanings of malleable and ductile.

Answer: 

Malleability: Metals can be beaten into thin sheets. This property is called malleability. Gold and silver are the most malleable metals.

 Ductility: The ability of metals to be drawn into thin wires is called ductility. Gold is the most ductile metal.

3. Why is sodium kept immersed in kerosene oil? 

Answer:  Sodium metal reacts so vigorously with oxygen in air 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.

4. Write equations for the reactions of 

(i) iron with steam 

(ii) calcium and potassium with water 

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

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

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

                    

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. 

Answer: (i) B is most reactive metal.

              (ii)  If B is added to a solution of Copper(II) sulphate it will eliminate copper from the solution.

                (iii) B>A>C>D

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. 

Answer: When dilute hydrochloric acid is added to a reactive metal hydrogen gas is produced.

                Chemical reaction when iron reacts with dilute H2SO4 is-

                

                            Fe (s) + H2SO4 (aq) → FeSO4( aq) + H2(g)

7. 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 active than iron. Therefore, if zinc metal is added to the iron (ll) sulphate solution, the iron will be removed to produce zinc sulphate and hence the green color of the iron (ll) sulphate solution will become colorless.

The reaction that took place is-

                            Zn(s) + FeSO₄ (aq)  → ZnSO₄ (aq) + Fe(s) 

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? 

Answer: (i) Electron-dot structures for sodium, oxygen and magnesium are-

                                                        

(ii) Formation of  Na2O-

(iii) Ions present in Na2O are sodium cation(Na⁺) and oxygen anion(O^2-). Ions present in MgO are magnesium cation (Mg⁺) and oxygen anion (O^2-). 

9. Why do ionic compounds have high melting points?

Answer: Due to the strong force of inter-ionic electrostatic attraction, it needs a lot of heat energy to separate the oppositely charged ions, hence the melting point of ionic compounds are very high.

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

Answer:     (i) Mineral - Metals are found in nature as  free elements or compounds. The earth's crust is the main source of metal. Seawater also contains some soluble salts, such as sodium chloride and magnesium chloride etc. Materials found in the earth's crust in the form of elements or compounds are called minerals. Eg. Gold, Platinum, zinc sulphide etc.

                    (ii) Ore - Some minerals contain high percentage of some metals and can be used to extract those metals profitably. This type of mineral is called ore. Eg. Cinnabar (HgS) is ore of mercury, Zinc Sulphide (ZnS) is ore of zinc.

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

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

Answer: Two metals found in free state in nature are Gold and Platinum.

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

Answer: The reduction method is used to produce metals from oxides. 

        The ores of metals low in the activity series are reduced to the corresponding metal only by heating the oxide of the ore.

                    2HgO (s) Heat → 2Hg (l) + O2 (g)

        The metals in the top of the activity series can be obtained by heating the oxide of the ore with carbon.

                    ZnO (s) + C (s) heat → Zn (s) + CO (g)

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? 

Answer: Displacement Reactions will take place in following cases-

Metal	Zinc	Magnesium	Copper
Zinc Oxide		Displacement	No Reaction
Magnesium Oxide	No Reaction		No Reaction
Copper Oxide	Displacement	Displacement

14. Which metals do not corrode easily? 

Answer: Metals at the very bottom of the activity series, such as gold, silver, etc., are less active metals and do not normally react to anyone. These metals, therefore, are not affected by acids, water vapour etc. Therefore, these metals do not corrode easily.

15. What are alloys? 

Answer: An alloy is a homogeneous mixture of two or more metals, or a metal and a nonmetal. It is prepared by first melting the primary metal, and then, dissolving the other elements in it in definite proportions. It is then cooled to room temperature. For example, brass is an alloy of copper and zinc (Cu and Zn), and bronze is an alloy of copper and tin (Cu and Sn).

EXERCISES

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. 

Answer: (d) AgNO3 solution 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. 

Answer: (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. 

Answer: (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. 

Answer: (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. 

Answer: (a) Metals are malleable. So if we beat it with a hammer, we can make a thin sheet out of it. But if we beat non-metals by hammer, it will break. Metals, can conduct electricity. So when  the battery and the bulb is connected with the help of the wire current will pass through it and the bulb will glow. But non-metals cannot conduct electricity. This is how we can distinguish between metals and non-metals.

(b) These tests may be quite useful in distinguishing between metals and non-metals. But, as some metals and non-metals show exceptional behaviour so, this method is not applicable to all metals and non-metals.

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

Answer: Metals oxides which react with both acids and bases to produce salts and water are called amphoteric oxides. Two examples of amphoteric oxides are zinc oxide (ZnO) and aluminum oxide (Al2O3).  

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

Answer:  The metals which are above hydrogen in the reactivity series can remove hydrogen from the dilute acids, whereas the metals below the hydrogen in the reactivity series can not remove the hydrogen from the dilute acid. For example metals like sodium, magnesium can remove hydrogen from light acids but copper, silver etc. cannot.

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

Answer: In the electrolysis of M metal a sheet of impure metal will be the anode, the cathode will be the thin sheet of pure M metal and the electrolyte will be the solution of M metal salts.

9. Pratyush took sulphur powder on a spatula and heated it. He collected the gas evolved by inverting a test tube over it,

 (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: (a) When sulphur is heated Sulfur dioxide is produced.

             (i) Sulfur dioxide does not react with dry litmus paper in any way.

          (ii) Sulfur dioxide reacts with wet litmus paper to convert blue litmus paper to red, as sulfur dioxide produces sulfuric acid when it comes in contact with water.

            (b) Balanced chemical equation for the above reaction is- 

                            S (s) + O₂ (g) → SO₂ (g)

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

Answer: Two ways to prevent rusting of iron is

    1. Painting: The surface of iron articles can be painted to prevent corrosion so that the metal is not exposed to water vapor.

    2. Galvanizing: Galvanizing is a method of applying zinc coating to steel and stainless steel. The metal does not affect from corrosion even after the zinc coating has been removed.

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

Answer: When non-metals combine with oxygen acidic oxides are formed. Eg. when carbon reacts with oxygen carbon di oxide is formed.

                            C (s) + O₂ (g) → CO₂ (g)

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. 

Answer: (a) Platinum, Gold and silver are less reactive and do not normally react with anyone. So, they do not corrode easily. They are more ductile, malleable and have metallic luster. Therefore, they are used to make jewellery.

(b) Sodium Potassium and Lithium metals are highly reactive because they react with oxygen so violently that they catch fire if kept in the open air. Therefore, they are immersed in kerosene oil to prevent accidents.

(c) Aluminum is a highly reactive metal yet it is used to make cooking utensils because aluminum reacts with the oxygen in the air to form a thin layer of aluminum oxide on its surface, which prevents further reaction. In addition it is cheap, good conductor of heat and has a high melting point.

(d) During the extraction of metals, carbonate and sulfide are converted to oxide because it is easier to extract metal from oxide than sulfide and carbonate. 

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. 

Answer: If a copper vessel is exposed to air for a long time, a green colored coating of copper carbonate forms on the vessel. Lemon juice contains citric acid and tamarind juice contains tartaric acid. These acids dissolves the green color coating of copper carbonate and cleans the vessel.

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

Answer: 1. Metals form electro-positive ions whereas non-metals form electro-negative ions.

                2. Oxides of metals are alkaline, oxides of non-metals  are acidic.

                3. Metals can remove hydrogen from dilute acids, non-metals cannot.

                4. Metals react with water to form oxides and hydroxides. Non-metals do not react with water.

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? 

Answer: The solvent used by fake goldsmiths is aqua regia. It is a freshly prepared mixture of concentrated hydrochloric acid (HCl) and concentrated nitric acid (NHO3) in the ratio of 3: 1. Acid can dissolve gold. This is why the bangles sparkled like new but their weight was reduced drastically. 

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

Answer: Copper is used to make hot water tanks but steel (iron alloy) is not used because copper is a good conductor of heat. Iron in hot water reacts with water vapour to form iron oxide. As a result, the steel will get rusted.