Chemical Effects of Electric Current Class 8 Question Answers
“Chemical Effects of Electric Current” is Chapter 8 taken from the JKBOSE textbook of Science for students of Class 8th. In the previous post, I provided you with Questions and Answers for Chapter 7 Combustion and Flame. This post is about the Chemical Effects of Electric Current Class 8 Question Answers. Before we move on to solutions you must have your basics clear. So, let me begin by giving you a brief overview of what you have studied in this chapter.
Chemical Effects of Electric Current Class 8 Question Answers
Overview of Chapter
- DO LIQUIDS CONDUCTS ELECTRICITY?
- CHEMICAL EFFECTS OF ELECTRIC CURRENT.
DO LIQUIDS CONDUCTS ELECTRICITY? The simple and straight answer to this question is Yes. Like solids, liquids also conduct electricity. The liquid solutions of acid, bases and salts in water conduct electricity. For Example, a solution of acids like hydrochloric acid, and sulphuric acid in water conducts electricity.
CHEMICAL EFFECTS OF ELECTRIC CURRENT: No chemical changes take place when electricity passes through solids, while in liquids, chemical changes take place when electricity is passed through them. This is called the chemical effect of electric current.
ELECTROPLATING: The process of depositing a thin layer of desired metal over a metal object with help of an electric current is called electroplating. Electroplating is a very useful process which is widely used in industry for coating metal objects with a thin layer of a different metal. Chromium plating is done on many objects such as parts of a car, bath taps, handlebars of motorbikes, rims of wheels etc.
Chemical Effects of Electric Current Class 8 Questions
- Fill in the blanks
(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.
- When the free ends of a tester are dipped into a solution, the magnetic needle shows deflection. Can you explain the reason?
Ans. When the free ends of a tester are dipped into a solution, the solution between the two ends of the tester allows electric current to pass through it and the circuit becomes complete. As a result, the wire having electric current in the circuit behaves like a magnet which causes a deflection in the needle of the compass. In other words, the deflection in the needle of the compass is due to the magnetic effect of electric current.
- Name three liquids, which when tested in the manner shown in Fig.8.9, may cause the magnetic needle to deflect.
Ans. The three liquids which may cause the magnetic needle to deflect when tested in the manner shown in fig 8.9 are
- Lemon Juice
- Salt Solution
- The bulb does not glow in the setup shown in Fig.14.10. List the possible reasons. Explain your answer.
Ans. Ans. There are four possible reasons for the bulb to does not to glow in the given circuit. These are:
- The connections are loose.
- The solution used in the setup is non-conducting.
- The battery used in the setup is used up.
- The bulb is fused.
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.
Ans. From the result, it is concluded that liquid A is a better conductor than liquid B.
6. Does pure water conduct electricity? If not, what can we do to make it conducting?
Ans. No pure water does not conduct electricity due to the absence of ions of salts in it. We can add a little amount of acid, base or salt to it to make it a conducting solution.
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.
Ans. Firemen must shut off the main electrical supply to the area before using water hoses to extinguish the fire. It is because water is a generally good conductor of electricity and if the main electric supply to the will remains on, it may result in the electrocution of the firemen.
8. A child staying in a coastal region test 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 deflection in the compass needle is produced due to the magnetic effect of electric current. The reason for more deflection in compass needles in the case of seawater is due to the presence of a large amount of dissolved salts in it. The presence of salts makes seawater a more conducting solution and it produces more current which produces a more magnetic effect and results in more deflection of a compass needle.
9. Is it safe for the electrician to carry out electrical repairs outdoors during heavy downpours? Explain.
Ans. No, it is not safe for an electrician to carry out electrical repairs outdoors during a heavy downpour because rainwater is a good conductor of electricity and it may result in a fatal electrical shock to the electrician.
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?
Ans. Rainwater is as pure as distilled water but when it rains, the rainwater gets mixed with suspended impurities and gases in the atmosphere and does not remain pure. As a result, rainwater becomes a conducting solution.
11. Prepare a list of objects around you that are electroplated.
Ans. The list of objects which are electroplated is as follows:
1. The wheel rims of bicycles, motorcycles and cars.
2. Bath taps and kitchen gas burners.
3. Handlebars and other components of the bicycle.
4. Artificial jewellery has the appearance of gold and silver.
5. Tin cans are used as storage containers for food items.
6. The items made of iron like bridges, railings and water pipes etc.
12. The process that you saw in Activity 14.7 is used for the purification of copper. A thin plate of pure copper and a thick rod of impure copper are used as electrodes. Copper from the impure rod is sought to be transferred to the thin copper plate. Which electrode should be attached to the positive terminal of the battery and why?
Ans. The impure copper rod is attached to the positive terminal of the battery while a thin plate of pure copper is attached to the negative terminal of the battery. It is because during the passage of electric current the electrode connected to the positive terminal of the battery loses copper into the solution to restore the loss of copper ions from the solution which gets deposited on the negative terminal of the battery.
That’s all about the Chemical Effects of Electric Current Class 8 Question Answers. Hope you found it useful. Do share your views about this post in the comment section below.