NCERT Solutions for Class 8 Science Chapter 14 Chemical Effects of Electric Current, contains solutions to various questions in Exercise for Chapter 14. At the end of the Solutions, all the keywords and Notes which are important to understand Science Chapter 14 Chemical Effects of Electric Current, have been explained in a simple and easy to understand manner. NCERT Solutions for Class 8 help to check the concept you have learnt from detailed classroom sessions and application of your knowledge.
| Category | NCERT Solutions for Class 8 |
| Subject | Science |
| Chapter | Chapter 14 – Chemical Effects of Electric Current |
Download NCERT Solutions for Class 8 Science Chapter 14-Chemical Effects of Electric Current
NCERT Solutions for Class 8 Science Chapter Chapter 14 Chemical Effects of Electric Current – NCERT Exercises
Question 1
Fill in the blanks
(a) Most liquids that conduct electricity are solutions of , _______ and _______.
(b) The passage of an electric current through a solution causes _______ effects.
(c) If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the _______ terminal of the battery.
(d) The process of depositing a layer of any desired metal on another material by means of electricity is called _______.
Answer 1.
(a) Most liquids that conduct electricity are solutions of acids, bases and salts.
(b) The passage of an electric current through a solution causes chemical effects.
(c) If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the negative terminal of the battery.
(d) The process of depositing a layer of any desired metal on another material by means of electricity is called electroplating.
Question 2
When the free ends of a testerare dipped into a solution, the magnetic needle shows deflection. Can you explain the reason?
Answer 2.
Yes, we can explain the reason. When the free ends of a tester are dipped into a solution then the magnetic needle shows deflection because the circuit gets completed and the deflection indicates that the solution is a good conductor of electricity.
Question 3
Name three liquids, which when tested in the manner shown in Fig.14.9, may cause the magnetic needle to deflect.
Answer 3.
Tap water, hydrochloric acid and sodium hydroxide cause the magnetic needle to deflect.
Question 4
The bulb does not glow in the setup shown in Fig.14.10. List the possible reasons. Explain your answer.
Answer 4.
The possible reasons for the bulb not glowing may be:
- The connections of the circuits may be loose
- The liquid used may not be a conductor of electricity as a result of which the circuit remains incomplete
- The bulb used in the circuit may be fused
- The battery may have been used up already or is very weak causing a very weak current to flow through the circuit
Question 5
A tester is used to check the conduction of electricity through two liquids, labelled A and B. It is found that the bulb of the tester glows brightly for liquid A while it glows very dimly for liquid B. You would conclude that
(i) liquid A is a better conductor than liquid B.
(ii) liquid B is a better conductor than liquid A.
(iii) both liquids are equally conducting.
(iv) conducting properties of liquid cannot be compared in this manner.
Answer 5.
(i) Liquid A is a better conductor than liquid B
We arrive at this conclusion because the amount of current flowing through a solution depends on the conductivity of the solution mixture. Greater the conductivity, greater is the flow of current and greater is the brightness of the bulb
Question 6
Does pure water conduct electricity? If not, what can we do to make it conducting?
Answer 6.
No, pure water does not conduct electricity due to the absence of free ions. It can be made to conduct electricity by dissolving some salt or acid or base in it resulting in dilution of water and release of some ions.
Question 7
In case of a fire, before the firemen use the water hoses, they shut off the main electrical supply for the area. Explain why they do this.
Answer 7.
This is so because the water used to douse the fire by the firemen may be conducting in nature and may conduct electrical current if the electrical supply is not switched off. Therefore, in order to prevent themselves from an electric shock, the firemen shut off the electric supply in the area.
Question 8
A child staying in a coastal region tests the drinking water and also the seawater with his tester. He finds that the compass needle deflects more in the case of seawater. Can you explain the reason?
Answer 8.
The sea water has greater amount of salt content present in it as compared to the normal drinking water. Thus, sea water is actually a better conductor of electricity than drinking water which explains the greater deflection of the compass needle.
Question 9
Is it safe for the electrician to carry out electrical repairs outdoors during heavy downpour? Explain.
Answer 9.
No, it is not safe for the electrician to carry out electrical repairs outdoors during heavy downpour because during heavy downpour there is a high risk of electrocution occurring to the person.
Question 10
Paheli had heard that rainwater is as good as distilled water. So she collected some rainwater in a clean glass tumbler and tested it using a tester. To her surprise she found that the compass needle showed deflection. What could be the reasons?
Answer 10.
This is so because rainwater is as good as distilled water, however it contains some impurities and dissolved salts present in it. Due to this, it is a better conductor of electricity and shows greater deflection than distilled water.
Question 11
Prepare a list of objects around you that are electroplated.
Answer 11.
A list of objects around us that are electroplated include-
Rim of vehicles, handle bars of bicycles and motorcycles, taps, kitchen gas burner, handles of doors etc.
Question 12
The process that you saw in Activity 14.7 is used for purification of copper. A thin plate of pure copper and a thick rod of impure copper are used as electrodes. Copper from impure rod is sought to be transfered to the thin copper plate. Which electrode should be attached to the positive terminal of battery and why?
Answer 12.
Electrode of impure copper should be connected with the negative terminal and positive terminal should be connected to the pure copper rod. This is so because pure copper metal, which is positively charged, from positive terminal is deposited over the negative terminal of thin copper after dissolving in the solution. The process referred to here is known as electroplating.
Topics Covered in Chapter 14 Chemical Effects of Electric Current Class 8 Science :-
- Do Liquids Conduct Electricity?
- Chemical Effects of Electric Current
- Electroplating
Important Terms Relevant to understand NCERT Solutions for Class 8 Science Chapter 14 Chemical Effects of Electric Current
Current: The normal flow of the electrical charges across a cross-sectional area per unit time is known as current.
Electrode: Electrode is a solid metallic conductor that is used to make contact with the non-metallic parts of a circuit and allow current to enter or leave an object/circuit.
Electroplating: The process of deposition of any desired metal over any other material by means of passage of electricity into a solution is called electroplating.
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