NCERT solution for class 8 // Science // Chapter 4 -Materials - Metals and Nonmetals

 NCERT solutions > class 8 science chapter 4 materials metals and nonmetals

NCERT solution for class 8  // Science // Chapter 4 -Materials - Metals and Nonmetals


Chapter 4 -Materials - Metals and Nonmetals

Q1. Which of the following can be beaten into thin sheets 

a) Zinc.  b)  Phosphorus   c) Sulphur.  d)  Oxygen 

Answer - Zinc

Q2. Which of the following statement is correct 

a) All metals are ductile 

b) All non metals are ductile 

 c) Generally metals are ductile 

d) Some  non metals are ductile  

Answer - Generally metals are ductile

Q3. Fill in the blanks 

a) Phosphorus is a very ------- nonmetal.

b) Metals are ------ conductor of heat and ------

c) Iron is ------- reactive than copper.

d) Metals react with acid to produce---------- gas

Answer

 a) Phosphorus is a very reactive nonmetal.

b) Metals are good conductor of heat and electricity. 

c) Iron is more reactive than copper.

d) Metals react with acid to produce hydrogen gas. 

Q4. Mark T if the statement is true and F if the statement is false

a) Generally non metals react with acids 

b) Sodium is a very reactive metal 

c) Copper displace zinc from zinc sulphate solution 

d) Coal can be drawn into wires  

Answer- 

 a) False  

 b) True    

c)False    

d) False

Q5 . Some properties are listed in the following table distinguish between the metals and nonmetals on the basis of these properties 


Answer

Q6. Give reasons for the following 

a) Aluminium foil are used to wrap food items 

b) Immersion rods for heating liquids are made up of metallic substance 

c) Copper cannot displace zinc from its salt solution

d) Sodium and potassium are stored in kerosene

Answer- 

a) Aluminium metal has a good malleable property so it can be mould into thin sheets and it does not react with the food atoms fastly so it is used for wrapping of food material 

b) Metals are very good conductor of heat in images drought used for heating liquids which is made up of the metallic substance and it transfer the heat to the liquid 

c) Copper can't replace the zinc sulphate solution because only a higher reactive metal can be displace the less reactive metal from its aqueous salt solution but the reactivity of the copper is less than zinc .

d) Sodium and potassium are very reactive metal they immediately catches fire if present in air and it also react with water but they does not react with kerosene that they are stored in kerosene 

Q7. Can you store lemon pickle in an aluminium utensils explain? 

Answer- 

Lemon has a citric acid and the metal are react with acid and liberated hydrogen gas hence lemon pickle can't be kept in aluminium utensil because it react with citric acid and liberate hydrogen

Q8. Match the substance given in a column A with their uses given in a column B 

Column A                            Column B

a) Gold                               Thermometer

b) Iron                               Electric wire

c) Aluminium                 Wrapping food

d) Carbon                        Jewellery

e) Copper                        Machinery

f) Mercury                     Fuel  

Answer - 

ColumnA                         Column B

a) Gold                               Jewellery

b) Iron                                Machinery

c) Aluminium                 Wrapping food

d) Carbon                        Fuel  

e) Copper                       Electric wire

f) Mercury                  Thermometer


Q9 . What happens when 

a) Dilute sulphuric acid is poured on the copper plate 

b)  Iron nails are placed in copper sulphate solution 

 Write word equation of the reaction involved 

Answer-.

 a)  when acid is react with metal it liberate hydrogen gas so if dilute sulphuric acid is poured on the copper plate the bubbles of the hydrogen gas forms on  the plate  

Cu + H2SO4 →CuSO4 + H2 

Copper + Sulphuric acid  →Copper sulphate + Hydrogen gas

b) when the iron nail placed in copper sulphate solution it becomes blue colour solution turns into green because we know that more reactive metal displace the less reactive metal from its salt solution and iron is more reactive than copper so it displays the sulphate ions from the copper  and form ferrous sulphate 

Fe + CuSO4    → FeSO4 + Cu 

Iron + copper sulphate→ ferrous sulphate + copper


Q10 . Saloni took a piece of burning charcoal and collected the gas evolved in a test tube 

a) How will she find the nature of the gas 

b) Write down the word equation of all the reasons taking place in this process 

Answer-

a) After burning a charcoal collecting the gas evolved in a test tube and add some drops of water in the test tube cover the test tube and shake it well then put the few drops of the solution on Blue litmus paper and red litmus paper if the blue litmus paper turns rate than the nature of gas is acidic and hit the red litmus paper turns blue than the gas is basic in nature 

b) Reaction taking place in this process are 

C+ O2 →CO2 

Carbon + oxygen → carbon dioxide 

CO2  + H2 O → H2CO3 

Carbon dioxide + water →carbonic acid 

Q11 . One day reeta went to a jewellery shop with her mother.  mother gave an  old gold jewellery to the goldsmith to polish next day when they bought a jewellery back they found that there was a slight loss in its weight can you suggest the reason for the loss in the weight 

Answer- 

During the polishing process the gold ornaments place Aqua regia ( mixture of HCl and HNO3in 3:1 ratio)due to this the gold layers start dissolving and which causes the reduction in weight the outer and polish layer desert and the layer become shiny 

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