8th std science metals and non metals question paper in english version2020-21

Information's | Sunday, 2 May 2021

 


Class–VIII (CHAPTER-04) Materials Metals and Non-Metals

Questions




1. Which of the following can be beaten into thin sheets? (a) Zinc (b) Phosphorus (c) Sulphur (d) Oxygen.

2. Which of the following statements is correct? (a)  All metals are ductile.

(b)  All non-metals are ductile.


(c)  Generally, metals are ductile. (d)  Some non-metals are ductile.

3. Fill in the blanks in the following statements. (a)  Phosphorus is a very         non-metal.

(b)  Metals are         conductors of heat and              . (c)  Iron is              reactive than copper.

(d)  Metals react with acids to produce                gas.


4. Mark 'T' if the statement is true and 'F' if it is false. (i)   Generally, non-metals react with acids. ( )

(ii)  Sodium is a very reactive metal. ( )


(iii) Copper displaces zinc from zinc sulphate solution. ( ) (iv) Coal can be drawn into wires. ( )

5. Some properties are listed in the following Table. Distinguish between metals and non-metals on the basis of these properties.


Properties             Metals      Non-metals 



1. Appearance


2. Hardness


3. Malleability


4. Ductility


5. Heat Conduction


6. Conduction of

Electricity




6.   Give reasons for the following.


(a)  Aluminium foils are used to wrap food items.


(b)  Immersion rods for heating liquids are made up of metallic substances.

(c)  Copper cannot displace zinc from its salt solution. (d)  Sodium and potassium are stored in kerosene.

7.   Can you store lemon pickle in an aluminium utensil? Explain.


8.   Match the substances given in Column A with their uses given in


Column B.


A B

(i) Gold (a) Thermometers

(ii) Iron (b) Electric wire


(iii)

Aluminum

(c) Wrapping food

(iv) Carbon (d) Jewelry

(v) Copper (e) Machinery

(vi) Mercury (f) Fuel

 


9.   What happens when


(a)  Dilute sulphuric acid is poured on a copper plate? (b)  Iron nails are placed in copper sulphate solution? Write word equations of the reactions involved.

10. 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 word equations of all the reactions taking place in this process.

11. One day Reeta went to a jeweler’s shop with her mother. Her mother gave an old gold jewelry to the goldsmith to polish. Next day when they brought the jewelry back, they found that there was a slight loss in its weight. Can you suggest a reason for the loss in weight? 


Class–VIII (CHAPTER-04) Materials Metals and Non-Metals

Answers





1.   (a) Zinc


2.   (c) Generally, metals are ductile


However, mercury is a liquid metal at room temperature cannot be drawn into thin wires and is not ductile.

3.   Fill in the blanks in the following statements.


(a)   Phosphorus is a very  reactive non-metal.


(b)   Metals are good conductors of heat and  electricity. (c)   Iron is more reactive than copper.

(d)   Metals react with acids to produce  hydrogen gas.


4.


(a)  Generally, non-metals react with acids. (F) (b)  Sodium is a very reactive metal. (T)

(c)  Copper displaces zinc from zinc sulphate solution. (F)


(d)  Coal can be drawn into wires. (F)





5.



Properties

Metals

Non-metals


1.Appearance

2. Hardness

3. Malleability



4. Ductility

Lustrous

Hard

Can be beaten into thin sheets

Dull

Soft

Cannot be beaten into thin sheets

 

 

5. Heat conduction

6.Conduction of Heat and electricity

 

Can be drawn into thin wires

Good conductors of heat and electricity

 

Cannot be drawn into thin wires

Poor conductors of heat and electricity 







6.


(a)   Aluminium foils are used to wrap food items because aluminium metal can be drawn into thin sheets(mallable).

(b)   Immersion rods for heating liquids are made of metallic substances because metals are good conductors of heat and electricity.

(c)   Copper cannot displace Zinc from its salt solution because Copper is less reactive than Zinc. This can be better understood from metal reactivity series.

Cu(s) + ZnSO4 (aq) → No reaction


(d)  Sodium and potassium are stored in kerosene because


they are highly reactive with oxygen present in atmosphere.


7. Lemon pickle cannot be stored in aluminium utensils because lemon pickle contains acids. Acids react with aluminium liberating hydrogen has which will lead to spoilage of pickle. 


8.


A B

(i) Gold (d) Jewelry

(ii) Iron (e) Machinery

(iii) Aluminum (c) Wrapping food

(iv) Carbon (f) Fuel

(v) Copper (b) Electric wire

(vi) Mercury (a) Thermometers

 

9.

























10.

 




(a)   When dilute sulphuric acid is poured on a copper plate, the copper metal reacts with sulphuric acid to liberate hydrogen gas.


 




(b)   When iron nail is placed in copper sulphate solution. Iron displaces copper form copper sulphate solution forming copper and Iron sulphate. Iron is more reactive than Copper.


 







(a)   On adding a few drops of water in the test tube containing gas. Gas is dissolved in water. Now, Test the solution of gas and water with blue litmus. The blue litmus changes its colour to red, indicating acidic nature of gas.

(b)   Burning of charcoal liberates Carbon dioxide gas 





Carbon dioxide gas reacts with water to form carbonic acid, which turns blue litmus red.

 


11. To polish the old gold jewellery, It is dipped in a solution called Aquaregia (1:3 molar ratio of HNO3 and HCl). The outer layer of the golden jewellery is dissolved in Aquaregia. The loss of outer layer causes reduction in w


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