Chemical Effects of Electric Current Question Answers: NCERT Class 8 Science

Welcome to the Chapter 14 - Chemical Effects of Electric Current, Class 8 Science - NCERT Solutions page. Here, we provide detailed question answers for Chapter 14 - Chemical Effects of Electric Current.The page is designed to help students gain a thorough understanding of the concepts related to natural resources, their classification, and sustainable development.

Our solutions explain each answer in a simple and comprehensive way, making it easier for students to grasp key topics and excel in their exams. By going through these Chemical Effects of Electric Current question answers, you can strengthen your foundation and improve your performance in Class 8 Science. Whether you're revising or preparing for tests, this chapter-wise guide will serve as an invaluable resource.

Some liquids are good conductor of electricity and some are poor conductors.
Most of the liquids that conduct electricity are the solution of acid, base and salt.
The passage of an electric current through an conducting liquid causes chemical reactions and these final resulting effects are called chemical effects of current.
The process of depositing a layer of any metal on another material with the electricity is called electroplating.
Positive terminal of the cell is connected to the negative terminal of another cell. Such combination of two or more cells is known as battery.
The substances which allows the electric current to pass through them are called as good conductor of electricity.
The substances which does not allow the electric current to pass through them are called as bad conductor of electricity.
Electrode may be defined as the conductor through which electricity or current enters or leaves.
A semi-conductor device which is used in mobiles, computers and torches are known as LED (Light emitting Diode).

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Exercise 1 ( Page No. : 183 )

Q1	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 ofany desired metal on another material by means of electricity is called .
Ans:	(a) Acids and bases, salts Some of the acidic, basic and neutral solutions also conduct electricity. They allow the current to pass through them. (b) Chemical When current passes through a solution, it dissociate into ions, i.e. positive and negative ions. The process of decomposition of the solution is called as chemical effect. (c) Negative The solution dissociate into positively charges copper ions and negatively charged sulfate ions, when we pass electricity or current through a copper sulfate solution. Positively charged copper ions attached to plate which is connected to the negative terminal of the battery. (d) Electroplating Electroplating is done on metals, to prevent them from the rusting with the help of electricity.

Q2	When the free ends of a tester are dipped into a solution, the magnetic needle shows deflection. Can you explain the reason?
Ans:	This is due to the magnetic effects of the electric current. When the free ends of the tester are dipped into the solution, the circuits get completed and the current starts flowing through it. And, then the current carrying conductor behaves like a magnet. Hence, magnetic needle shows the deflection.

Q3	Name three liquids, which when tested in the manner shown in Fig.14.9, may cause the magnetic needle to deflect.
Ans:	Lemon juice (citric acid) C₆H₈O₇, Vinegar (Acetic acid) H₃COOH, Hydrochloric acid (HCl), salt (NaCl). Because these solutions allow electricity to pass through them.

Q4	The bulb does not glow in the setup shown in Fig.14.10. List the possible reasons. Explain your answer.
Ans:	The bulb may not glow in the given setup due to the following reasons: The liquid may not contain ions or charged particles. The bulb may be fused. Cells which are used in the battery may be used up. The connecting wire may be broken up. Connection may be loose.

Q5	A tester is used to check the conduction of electricity through two liquids, labeled 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.
Ans:	(i) Liquid A is better conductor than liquid B The amount of electric current flowing through a conducting solution always depends on the conductor of the solution. More current can pass through the solution with more conductivity and vice versa. So, the conductivity of liquid A is more than liquid B.

Q6	Does pure water conduct electricity? If not, what can we do to make it conducting?
Ans:	No, pure water does not conduct electricity because pure water does not contain ions to conduct electricity. In order to make it conducting, we should add salt, acid and base in the water. Hence, water conducts electricity.

Q7	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.
Ans:	Because water is a good conductor of electricity. Hence, a fireman may get an electric shock. So, in order to prevent from the electric shock they first shuts off the main electrical supply of that area.

Q8	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?
Ans:	The compass needle deflects more in the case of sea water because it contains a large amount of dissolved salt which makes it a good conductor of electricity than the drinking water.

Q9	Is it safe for the electrician to carry out electrical repairs outdoors during heavy downpour? Explain.
Ans:	No, it is not safe because rainy water contains a large amount of (salt) impurities like acids, minerals etc. which makes the rain water a good conductor of electricity and the electrician may get an electric shock.

Q10	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?
Ans:	Rain water contains a large amount of impurities like acids, minerals etc. which makes the rain water a good conductor of electricity and the compass needle shows deflection.

Q11	Prepare a list of objects around you that are electroplated.
Ans:	Chromium plating is done on many objects such as car parts, bath taps, kitchen gas burners and many others. Jewellary makers electroplate silver and gold on expensive metals. Tin cans used for storing food that are made by electroplating tin onto iron. Iron is used in bridges automobiles to provide strength. That’s why a coating of zinc is deposited on iron to protect it from corrosion and from the formation of rust.

Q12	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?
Ans:	The thin plate of pure copper is connected to the negative terminal of the battery to make it cathode, while the thick rod of impure copper is connected to the positive terminal of the battery to make it anode; because the copper forms positive ions which are attracted to the electrode and connected to the negative terminal of the battery and gets deposited over it.