Sunday, 13 January 2019

CBSE Class 8 - Science - Chemical Effects of Current (Worksheet)(#cbsenotes)(#eduvictors)(#class8Science)

Chemical Effects of Current 

Class 8 - Science 

CBSE Class 8 - Science - Chemical Effects of Current (Worksheet)(#cbsenotes)(#eduvictors)(#class8Science)


(Worksheet)

Q1: Fill in the blanks

a. If electrodes are immersed in water and current is passed, bubbles of ________ and _______ are produced.

b. A coating of ______ is deposited on the iron to protect it from corrosion and formation of rust.


Q2: Circuit of the tester may be complete yet the bulb may not glow. Why?

Answer:
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Q3: Why does a bulb glow when an electric current is passed through it?

Answer:
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Q4: Why should we never handle electrical appliances with wet hands or while standing on a wet floor?

Answer:
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Q5: What are the byproducts of electrolysis of copper sulphate?

Answer:
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Q6: List the changes seen in the liquid when an electric current is passed through it?

Answer:
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Q7: What happens when an electric current passes through a potato and give reasons also?

Answer:
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Q8: Does distilled water conduct electricity? If not how can we make it conducting?

Answer:
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Q9: It has been observed that ornaments used by women appear to be made of gold but with repeated use, the gold coating wears off, revealing some other metal beneath. Explain the possible reason.

Answer:
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Q10: Name the scientist who performed electrolysis of water and showed that Hydrogen and Oxygen gas evolve at electrodes.

Answer:

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Answers:
1: (a) Oxygen, Hydrogen
(b) Zinc

2: i.  Connections may be loose
ii. The battery may be discharged
iii. Fused bulb
iv. weak electrolyte

3: Due to the heating effect, the filament of the bulb gets heated up at high temperature and starts emitting light.

4: Water is a good conductor of electricity and we can get an electric shock.

5: Copper starts depositing at Cathode. Oxygen Gas evolved at the anode if we use Carbon electrodes. Impurities called Anode mud also settle at the bottom below anode.

6: (i) Change in colour
   (ii) Evolution of gas
   (iii) Deposit of metal at the cathode.

7: When copper wire inserted into a potato carries current, it does electrolysis of copper in starch solution present in potato.  A compound of copper forms which appears as a bluish green spot.

8: Distilled water does not contain any ions (charged particles) and is a poor conductor of electricity. By adding salt (e.g. sodium chloride) leads to the formation of ions and make the solution conducting.

9: God coating was electroplated on some cheap metal. Due to repeated use, the coating wears off.

10: William Nicholson

☛See also:
Ch 14 - Chemical Effects of Electric Current (NCERT Solutions)
Ch 14 - Chemical Effects of Electric Current (MCQs)
Ch 14 - Chemical Effects of Electric Current (Q & A)
Ch 14 - Chemical Effects of Electric Current (Worksheet)
Ch 14 - Chemical Effects of Electric Current (Worksheet-2)

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