NCERT solution for class 10th // Science // Chapter 3 -Metals and nonmetals

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NCERT solution for class 10th  // Science  // Chapter 3  -Metals and nonmetals 

Chapter 3  -Metals and nonmetals

                        Page number 40 

Q1. Give an example of a metal which is a liquid at room temperature can be easily cut with a knife 

a) Is the best conductor of heat  

b) Is a poor conductor of heat 

Answer

 Mercury sodium silver Lead

Q2. Explain the meaning of malleable and ductile 

Answer-

 Malleable 

A substance for material which can be beaten into thin sheets is called malleability metals are good malleable metals like silver and gold are converted into a very thin sheet 

Ductile 

A substance is a capable of beaten into draw being drawn into thin wires is called ductility. Metals are good ductile metal like  gold and silver can be converted into very thin wires

                        Page number 46 

Q3. Why is Sodium kept immersed in kerosene oil.?

Answer

 Sodium is very high reactive metal when it kept in open air . It vigorously reacts with oxygen and catches fire therefore to protect  an accidental fire sodium is kept in kerosene oil because it does not react with kerosene oil .

Q4. Write equation for the reaction of 

 a) Iron with steam 

  b) Calcium and potassium with water 

Answer-

  i) 3Fe+ 4 H₂O    →   Fe₃O ₄ + 4 H₂  

ii) a) Ca + 2 H₂O   →    Ca (OH)₂ 

b) 2 K + 2 H2O   →   2 KOH + H₂

Q5. Samples of four metals A,B,C and D were taken and added to the following solution one by one the result obtained have been tabulate as following 

Metal	Iron sulphate	Copper 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 question about metals A,B,C,D,and D 

a) Which is the most reactive metal

b) What would you observe if b is added to a solution of copper sulphate 

c) Arrange the metals A,B,C and D in the order of decreasing reactivity 

Answer 

i)  B is the  most active metal as it displace iron from its salt solution 

ii)  B will display cu from cuso4 solution because B is more reactive than copper 

iii)  B    >A   >C   > D

Q6. Which gas is produced when dilute hydrochloric acid is added to the reactive metal write the chemical reaction when iron reacts with dilute H2 s o4 

Answer 

Hydrogen gas is produced when dilute hydrochloric acid is react with metal 

Fe + H₂ SO₄       →   FeSO₄ + H₂

Q7 . What would you observe when zinc lb added to a solution of iron sulphate write the chemical reaction that takes place 

Answer-

 Zinc is more reactive than iron so it displace  the iron from iron sulphate solution and the green colour of the solution fades of the iron metal gets deposited on it 

Zn + FeSO₄   →    Zn SO₄+ Fe 

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Q8 .  a) Write the electron dot structure of for Sodium Oxygen and magnesium ? 

b)  Show the formation of Na2O and MgO by the transfer of electrons 

c) What are the ions present in these compounds

Answer- 

a)

Element	Atomic number	Electronic configuration	Electron dot structure
Na	11	(2,8,1)	.     Na
O	8	(2,6)	.. : O :
Mg	12	(2,8,2)	: Mg

 b) 

iii )  Na2O  has  Na₂^{+   and} O^2-ions 

^{MgO has} Mg₂^{+    and} O^2-ions 

Q9. Why do ionic compounds have high melting points 

Answer-

 In ionic compound the ionic bond or  electrostatic force of attraction is a very strong . It has a strong force of attraction between the oppositely charged ions when the compound is heated the lots of the heat energy is consumed by it to break the strong electrostatic force of attraction during melting therefore ionic compounds have high melting and boiling point

                        Page number 53. 

Q10. Define the following term

a) Minerals       b) Ore   c) Gangue

 Answer 

a) Minerals 

The naturally occurring elements are compounds of metal present in the earth crust are called minerals 

b)Ore 

Ore are the minerals containing metal from which a particular metal can be extracted for profit 

c) Gangue 

The unwanted or undesirable impurities present in the metal ore are called gangue

Q11. Name two metals which are found in nature in the free state

Answer -

 Gold and platinum are found in free state in nature

Q12. What chemical process is used for obtaining a metal from its oxide 

Answer-

Reduction process is used to  separate the metal from its oxide this reduction can be done by heating with carbon for by using highly reactive metal such as sodium calcium and Aluminium the reaction is exothermic large number of heat is produced so the metal is produced in molten form . 

Z n o + C       →    Zn + CO 

                Page number 55

Q13 . Metallic oxide 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 reaction taking place

Answer- 

zinc will react with copper oxide and it displays copper magnesium will react with zinc and form zinc oxide and the copper from copper oxide it means that copper being least reactive will not react with any of the given oxide 

Metal	zinc	magnesium	copper
Zinc oxide	-	yes	-
magnesium oxide	-	-	-
copper oxide	yes	yes	-

Q14. Which metals do not corrode easily

Answer 

Low reactivity series metal do not be corroded easily 

Eg - Gold ,Silver ,Platinum etc.

Q15. What are alloys

Answer- 

An alloy is a homogenous mixture of two or more metals or  metals and a nonmetals combine to form a more durable compound electrical conductivity and the melting point of the alloy is less than that of a pure metal 

Example- Steel  = iron + zinc 

Stainless steel  = iron + metal + chromium + zinc

                    Exercise 

Q1. 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 in copper metal 

Answer- 

d) AgNO₃  solution in copper metal  

Copper metal displace silver because copper is more reactive than silver 

2AgNO₃ + Cu   →Cu(NO3)₂ + 2 Ag

Q2.  Which of the following method is suitable for preventing an iron frying pan from rusting 

a) Applying grease 

b) Applying paint

 c) Applying  coating of zinc

d) All the above  

Answer-

Applying a coating of zinc will prevent the iron frying pan from rusting

Q3. An element react with oxygen to give a compound with a high melting point This compound is also soluble in water the elements is likely to be 

a)calcium 

b) carbon  

c) silicon 

d) iron

Anwers-

 The compound is calcium because it combines with oxygen to give CaO calcium oxide

Q4. 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- 

Zinc is more reactive than tin

Q5. 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 nonmetals 

b) Asscess the usefulness of these tests in distinguishing between metals and nonmetals

Answer -

 a ) Take sample of given materials of metals and nonmetals in strike hammer on it if it convert into thin sheet then it is metal if not then it is non metal 

When a hammer strike on the both material the metals produce sound their nonmetals not produce any sound 

When both the substance are arranged in electric circuit the metals can conduct electricity while non metal cannot be conduct electricity

b) from above all test it is clear that the metals show malleable ,Sonorous ,good conductor of electricity  properties while  non metal are not shows such type of property

Q6. What are amphoteric oxides give two examples of amphoteric oxides 

Answer- 

The metallic oxide which shows the properties of acid as well as bases are called amphoteric oxide they are react with acid and bases to form salt and water and that reaction we called neutralization reaction 

ZnO +  HCl    →ZnCl₂ + H₂O

ZnO+ 2NaOH.      →    Na₂ZnO₂ +  H₂O

Q7. Name two metals which will displace hydrogen from dilute acids and two metals which will not 

Answer-

 Zinc and magnesium displace H₂from dilute acid while copper and silver do not able to displace the H₂

Q8. In the electrolytic refining of a metal M what would you take as anode the cathode and the electrolyte?

Answer-

•  Anode is used as a a metal M it is positively charged 
•  Cathode is used as a strip of pure metal M which is negatively charged 
•  Electrolyte is the aqua solution of salt of metal m

Q9 . Pratyush took sulphur powder on the 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 

Answer  

a) i) No change in colour in dry blue litmus 

ii ) Moist blue litmus paper will change into red colour because sulphur is non metal and non metal oxides are acidic in nature

b) S + O₂      →  SO₂

_SO2 + H₂O    →     H₂SO₃

Q10. State two ways to prevent the rusting of iron

Answer  

Two methods for preventing rusting of iron are 

• Applying paint on the iron articles for greasing to the iron articles prevent rusting process 
• Galvanization process is also avoid the rusting of iron in this process the zinc metal is coated on the iron surface

Q11. What type of oxide are formed when nonmetals combine with oxygen

Answer  .

Non metals form acidic oxide in their aqueous solution 

C + O_2.     →    CO₂ 

CO₂ + H₂O    →     H₂CO₃ 

                        Carbonic acid  ---- blue litmus change into red

Q12. Give reason

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 highly malleable and least reactive metals they they are not corroded by air and water easily so they are used to make jewellery 

b) Sodium potassium and lithium are very high reactive metal. These metals are react radially with atmospheric oxygen to form oxide so to prevent the oxidation of the metal it stored in oil because it does not react with oil 

c) Aluminium is highly reactive metal but its oxide is less reactive so during the preparation of utensils the thin layer of Aluminium oxide covered on the aluminium to prevent the corrosion 

d) Extraction of metal from its oxide is more easy process than the extraction of metals from its carbonate and sulphide so carbonate and sulphide firstly converted into oxides and then the extraction of metal takes place

Q13. You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice explain why these so substances are effective in cleaning the vessels

Answer 

 When copper is reacted with atmospheric oxygen then copper carbonate is formed this is the thin layer present on the copper vessels. This layer is insoluble in water so it cannot be cleaned by water but it is soluble in acids present in lemons and tamarind contain citric acid and tartaric acid respectively so .A substance containing acid can be more effective in cleaning of the vessels made up of copper

Q14. Differentiate between metal and nonmetal on the basis of their chemical properties 

Answer  

Q15. Man went door to door posing as a goldsmith. He  promised to bring back the glitter of old and gold ornaments and unsuspecting lady gave a set of gold bangles to him which he dipped  in a particular solution the bangles sparkled  like a new but their weight was reduced drastically . The lady was upset but after a futile argument the man with the retreat can you play the detective to find out the nature of the solution he had is used .

Answer  

The man used ACqua regia mixture it is only a solution which can dissolve the gold and due to that dissolving process their weight was reduced drastically. Aqua regia is a mixture of concentrated HCL concentrated HNO3 in the ratio of 3: 1

Q16. Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron) 

Answer-  

Iron is more reactive than the copper when it come in contact with hot steam it formed Fe3O4 so the body of tank is made up of copper but not  steel because copper does not react with water 

3Fe+ 4 H₂O  →    Fe₃O ₄ + H₂O