Chemical Effects of Electric Current NCERT Solutions - Class 8 Science

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 _________.

Ans:  

a) Most liquids that conduct electricity are solutions of acids, bases and salts. 

(The solutions of acids, bases, and salts can conduct electricity because they produce ions when dissolved in water and allow an electric current to pass through them.) 

b) The passage of an electric current through a solution causes chemical effects. 

(A chemical reaction occurs when an electric current passes through a conducting solution. As a result, the solution decomposes into positive and negative ions. This process of decomposition of the solution is known as the chemical effect of electric current.) 

c) If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the negative terminal of the battery. 

(Copper sulphate decomposes into positively charged copper ions and negatively charged sulphate ions when an electric current is passed through it. These positively charged copper ions get drawn towards the plate (cathode) connected to the negative terminal of a battery and get deposited on it.) 

d) The process of depositing a layer of any desired metal on another material by means of electricity is called electroplating.

One of the most significant uses of the chemical effects of electric current is electroplating.

2. When the free ends of a tester are dipped into a solution, the magnetic needle shows deflection. Can you explain the reason? 

Ans: The deflection in the magnetic needle of a compass shows that current is flowing through the wire, i.e., through the circuit. This shows that the circuit is complete since the free ends of the tester are dipped in a conducting solution. A conducting solution allows electric current to pass through it and, as a result, the magnetic needle shows a deflection.

3. Name three liquids, which when tested in the manner shown in Fig. 14.9, may cause the magnetic needle to deflect.

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Ans: Liquids such as lemon juice, saltwater, and vinegar are conducting liquids that allow electricity to pass through them. Hence, these liquids can be used in the beaker to show the deflection of the magnetic needle.

4. The bulb does not glow in the setup shown in Fig. 14.10. List the possible reasons. Explain your answer.

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Ans:  The bulb may not glow for one or more of the reasons listed below:

1. The liquid in the beaker is maybe poor conducting. As a result, the electric current would not be able to flow through the liquid. Hence, the circuit is incomplete.

2. The electric current in the circuit is too weak to light the bulb. This can happen if the material used to make the circuit is not a good conductor of electricity or if the battery does not have enough energy to generate electricity.

3. The liquid may have a very low conductivity. So, the current flowing through the circuit may be insufficient to produce enough heat in the filament of the bulb to make it glow.

4. The battery may be used up and no longer be capable of generating electricity.

5. The bulb may be fused.

6. Connections are loose.
   
   

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 

1. liquid A is a better conductor than liquid B. 

2. liquid B is a better conductor than liquid A. 

3. Both liquids are equally conducting. 

4. Conducting properties of liquid cannot be compared in this manner.

Ans:  

1. Liquid A is a better conductor than liquid B. 

The amount of current flowing through a conducting solution is determined by its conductivity. The greater the conductivity, the greater the amount of current passing through the solution, and vice versa. The conductivity of liquid A is greater than the conductivity of liquid B. Hence, liquid A is a better conductor than liquid B.

6. Does pure water conduct electricity? If not, what can we do to make it conduct?

Ans: No, pure water does not conduct electricity as it is a poor conductor of electricity. Pure water (distilled water) is devoid of any salts. They can conduct electricity when a small amount of common salt is added to them, as the salt solution allows electricity to pass through.

7. In case of a fire, before the firemen use the water hoses, they shut off the main electrical supply of the area. Explain why they do this.

Ans: Water usually contains salts and has the ability to conduct electricity. If the area's electrical supply is not turned off and water is poured on electrical appliances, electricity may pass through the water. Electricity may harm firemen if they come in contact with wet electrical switches, electric wires, and other electrical appliances. They may get electrocuted. That is why, in the case of a fire, the main electrical supply for the area is shut off before they use the water hoses, to prevent the firemen from electrocution.

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 amount of dissolved salts present in the seawater is more than the water we use for drinking purposes. As a result, seawater will conduct electricity better than drinking water. So, the compass needle shows more deflection in seawater than in drinking water.

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 work on electrical appliances outdoors during a heavy downpour. This is because rainwater contains a small number of dissolved salts and acids, making it a good conductor of electricity. So, the electrician may get electrical shocks while working outdoors during heavy rains or downpours.

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 show deflection. What could be the reasons? 

Ans: Rainwater contains a small number of dissolved salts and impurities, making it a good conductor of electricity. Distilled water does not contain any dissolved salts or impurities; thus, it is a poor conductor of electricity. Hence, due to the presence of these salts and impurities, rainwater can allow electricity to pass through it and cause a deflection in the compass needle, while distilled water cannot.

11. Prepare a list of objects around you that are electroplated. 

Ans: The list of electroplated objects around us is as follows: 

1. Chromium plating: This is done on different parts of cars, motorcycles, and buses, to give them a shiny appearance. 

2. Gold Plating: A thin layer of gold is deposited by electroplating on the silver ornaments and they are called gold-plated ornaments. 

3. Zinc plating: Iron used in constructing buildings, bridges, and automobiles is coated with a layer of zinc (galvanization). This provides strength and protects the iron from corrosion and rusting.
   
   

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?

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Ans: The thick rod of the impure copper plate is to be attached to the positive terminal of the battery. This is because when the electric current is passed through the copper sulphate solution, it gets dissociated into positively charged copper ions and negatively charged sulphate ions. The free copper, being positively charged, gets attracted to the negative terminal of the battery and gets deposited on the electrode (cathode) attached to it. The loss of copper from the copper sulphate solution is regained from the impure copper rod (anode) connected to the positive terminal of the battery.

NCERT Solutions for Class 8 Science - Free PDF Download

Have you been struggling to find reliable study material for preparing for your upcoming exams? Vedantu has made it easier for you to grasp essential topics of Chemical Effects of Electric Current by offering free NCERT Solutions for Class 8 Chapter 14 in a PDF format that incorporates every topic and subtopic along with relevant question banks.

NCERT Solutions for Class 8 Science Chapter 14 - Chemical Effects of Electric Current

Topics Covered in Chapter Chemical Effects of Electric Current Class 8 Science

• Do Liquids Conduct Electricity?

• Chemical Effects of Electric Current

• Electroplating

Metals such as copper and aluminium are good conductors of electricity, but rubber and plastics are poor conductors. In the case of liquids, certain liquids are good conductors of electricity while others are poor conductors. Pumped water, well water, pond water, and tap water are not clean and include numerous dissolved salts. This type of water is an excellent conductor of electricity. Distilled water, on the other hand, is devoid of salt and is a poor conductor of electricity.

Important Points Discussed in Chapter

• Some liquids are good conductors of electricity, whereas others are not.

• The bulk of electrically conducting liquids is acid, base, and salt solutions.

• When an electric current flows through a conducting liquid, chemical reactions occur.  Chemical impacts of currents are the results of this process.

• Electroplating is the technique of depositing a coating of any chosen metal on another material using electricity.

Introduction to Electric Currents

This NCERT Solutions Class 8 Science Chapter 14 guide comprises 5 sections. The first section involves the introduction of core insights into electric current and how it works. Students will also understand why touching any electrical appliance with wet hands can be harmful. Further, Chemical Effects of Electric Current also looks into helping students understand how electricity moves from their bodies and which are some of the good conductors by which electricity can move effortlessly.

Also, students will learn what is defined as a poor conductor, what might stop electricity from passing from these poor conductors, the mechanism of working, and much more. Students can make use of the Science Chapter 14 Class 8 PDF to learn everything they need to know about electricity and if or not they can make use of certain materials for passing electricity. Chapter 14 also offers a wide range of examples for students to get a clear understanding of the working of electricity. Lastly, a few other topics that you will learn about include- do liquids conduct electricity and which types of solid conduct electricity.

14.1 Do Liquids Conduct Electricity?

While the introduction of chapter 14 deals with helping students grasp what electricity is all about, this section helps you understand whether liquids conduct electricity or not. This section includes performing a wide range of activities to conclude if or not liquids are good conductors of electricity. Students are advised to be careful and take necessary precautions throughout performing these experiments to have a safe yet knowledgeable experience. Every activity in this section aims at helping students learn more about the laws of electricity.

The NCERT Class 8 Science Chapter 14 Question Answer guide further offers students some details on why they shouldn’t use their bare hands while performing different tests. Moreover, students will also learn about the dangerous effects of electricity and how it can harm us. You will also get insights into the heating effect while transferring electricity through a specific filament of a bulb or even a copper wire connected with nails. Another intriguing concept that you’ll learn in this section is what is a weak and strong current.

14.2 Chemical Effects of Electric Current

The NCERT Science Class 8 Chapter 14 PDF also gives brief insights into the third part of the chapter, Chemical Effects of Electric Current. Here, students will learn more about the core effects of electric current. The entire chapter is based on physical experiments and activities that students need to perform to learn about the different effects of electric current.

This section thus involves understanding more about different effects produced after a current is passed through distinguishing conducting solutions. Students are also advised to read through these activity sections meticulously to learn how electricity produces certain effects and how students should secure themselves from getting shocks while performing these activities.

Moreover, you will gain more information about William Nicholson, a British chemist that performed several activities for analyzing different situations of electrodes when passed through water.

14.3 Electroplating

In the NCERT Solutions of Class 8 Science Chapter 14 guide, students will also learn about electrodes and some of their fundamental chemical effects. Additionally, there is an entire section based on electroplating. Students will be introduced to a completely new concept that deals with what happens when you pass electricity through a copper sulphate solution and how copper sulphate is dissociated from sulphate and copper, along with its brief mechanism.

You will further learn about different uses of electroplating in real life and its applications. The Class 8 Science Chapter 14 Solutions guide offers concise questions on this section to help students prepare well for exams.

Exercises

On thoroughly revising this chapter and performing distinguishing activities, you will have to go through the questionnaires on the same. You are asked to solve about 12 questions in this respective exercise. All these questions are entirely based on the above-mentioned 4 core topics and will test your understanding of the Chemical Effects of Electric Current. The questions may be a bit tricky to understand. Thus, students are asked to read each question twice before answering it.

Key Features of Ncert Solutions for Class 8 Chapter 14

Given below are a few of the prime features of NCERT solutions for class 8 Chemical Effects of Electric Current.

• Get precise knowledge of the different effects of electric current.

• Understand different precautionary measures to take while performing activities that involve passing electricity through an object.

• Learn more about the three topics that this chapter covers in-depth.

Chapter wise NCERT Solutions for Class 8 Science

• Chapter 1 - Crop Production and Management

• Chapter 2 - Microorganisms : Friend and Foe

• Chapter 3 - Synthetic Fibres and Plastics

• Chapter 4 - Materials : Metals and Non-Metals

• Chapter 5 - Coal and Petroleum

• Chapter 6 - Combustion and Flame

• Chapter 7 - Conservation of Plants and Animals

• Chapter 8 - Cell - Structure and Functions

• Chapter 9 - Reproduction in Animals

• Chapter 10 - Reaching The Age of Adolescence

• Chapter 11 - Force and Pressure

• Chapter 12 - Friction

• Chapter 13 - Sound

• Chapter 14 - Chemical Effects of Electric Current

• Chapter 15 - Some Natural Phenomena

• Chapter 16 - Light

• Chapter 17 - Stars and The Solar System

• Chapter 18 - Pollution of Air and Water

Along with this, students can also view additional study materials provided by Vedantu, for Class 8 :

• NCERT Exemplar for class 8 Science Chapter 14

• CBSE Revision Notes for class 8 Science Chapter 14