Read and download free pdf of CBSE Class 8 Science Chemical Effects of Electric Current Assignment Set A. Get printable school Assignments for Class 8 Science. Standard 8 students should practise questions and answers given here for Chapter 14 Chemical Effects Of Electric Current Science in Grade 8 which will help them to strengthen their understanding of all important topics. Students should also download free pdf of Printable Worksheets for Class 8 Science prepared as per the latest books and syllabus issued by NCERT, CBSE, KVS and do problems daily to score better marks in tests and examinations
Assignment for Class 8 Science Chapter 14 Chemical Effects Of Electric Current
Class 8 Science students should refer to the following printable assignment in Pdf for Chapter 14 Chemical Effects Of Electric Current in standard 8. This test paper with questions and answers for Grade 8 Science will be very useful for exams and help you to score good marks
Chapter 14 Chemical Effects Of Electric Current Class 8 Science Assignment
Question 1. Fill 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.
Question 2. When the free ends of a tester are dipped into a solution, the magnetic needle shows deflection. Can you explain the reason?
Answer- Yes, because solution is 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-Vinegar, Lemon juice and tap water.
Question 4. The bulb does not glow in the setup shown in fig. 14.10. List the possible reasons. Explain your answer.
Answer- The bulb may not glow because of the following reasons:
(i) Liquid in the beaker may be non-conducting.
(ii) The battery may be exhausted and does not have sufficient energy to generate electricity.
(iii) The bulb may be fuse.
(iv) Connections may be loose.
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.
Question 6- Does pure water conduct electricity? If not, what can we do to make it conducting?
Answer- No. Pure water does not conduct electricity. This is because pure water do not have any free ion. Pure water can conduct electricity when a pinch of common salt is added to it, as salt solution is conducting in nature.
Question 7. In case of fire, before the firemen use the water hoses, they shut off the main electric supply for the area. Explain why they do this.
Answer- Water usually contains salts and conducts electricity. If the electrical supply is not cut off and firemen come in contact with wet electric switches, electric wires and other electrical appliances, he can get electric shock.
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- Water we use for drinking purposes has very less amount of salts dissolved in it while sea water has very high concentration of salts in it. So, compass needle shows more deflection in case of sea water.
Question 9. Is it safe for the electrician to carry out electrical repairs outdoors during heavy rain pour? Explain.
Answer- No. It is not safe to repair electrical appliances outdoors during heavy downpour. This is because rain water contains small amounts of acids in it which makes it a conductor of electricity. So, the electrician may get electrical shocks while working outdoors during rain.
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 reason?
Answer- Rain water is said to be pure water. But many impurities and acidic gases get dissolved in the rain water while it falls to the earth through the atmosphere. Due to the presence of these impurities and small amounts of acids in it, the rainwater conducts electricity.
Question 11. Prepare a list of objects around you that are electroplated.
Answer- The objects which are electroplated are:
(i) Taps of water connection.
(ii) Parts of bicycle.
(iii) Body of cars, motor cycle and tractors.
(iv) Handles of the doors.
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 transferred to the thin copper plate. Which electrode should be attached to the positive terminal of the battery and why?
Answer- The thick rod of impure copper should be attached to the positive terminal of battery. This is because the copper ions of the solution will get deposited on the thin rod and the loss of copper from the solution will be restored from the thick rod to the positive terminal of the battery. Thus, copper from the thick rod could be extracted out..
ONE MARK MCQs
1. Veena has read that some substances are good conductors of electricity where as some are bad conductors. Among the following which substance is good conductor of electricity?
a) Copper b) Silver c) Iron d) All of the above (✓)
2. Today Rohit came to know that in the ancient times people used a device to detect direction. What was that device called?
a) Voltmeter b) Ammeter c) Magnetic Compass (✓) d) All of the above
3. Manish today read about various effects of electric current. Electric bulb works on which effect of electric current?
a) Heating effect (✓) b) Magnetic effect c) Chemical effect d) All of the above
4. Neeta's mother today brought gold plated silver jewelry. What is the process of plating one metal on another metal called?
a) Vaporization b) Electroplating (✓) c) Distillation d) All of the above
5. Dhruv was very happy to see traffic signals in the city. What kinds of lights are used in traffic signals?
a) Tungsten bulb b) LED bulb (✓) c) Neon bulb d) None of the above
6. Meenakshi broke a dry cell today. She got a black colored rod from it. What is this rod called?
a) Electrode (✓) b) Electrolyte c) Insulator d) All of the above
7. Heera singh is surprised that the flow of electric current breaks the water into hydrogen and oxygen. Can you tell me that due to which effect of current this happens?
a) Heating effect b) Chemical effect (✓) c) Magnetic effect d) All of the above
8. Today Baljinder saw in science lab that lemon juice is good conductor of electricity. Among the following which is good conductor of electricity?
a) Vinegar b) Tap water c) Tomato juice d) All of the above (✓)
9. Electricity repair is going on at sewak's house. He saw that handles of electrical repairing tools are made up of plastic. What is the reason for this?
a) Plastic is good conductor of electricity. b) Plastic is bad conductor of electricity. (✓)
c) Plastic generates electricity. d) None of the above.
10. Pankaj knows that pure water is bad conductor of electricity. If you dissolve salt in water what will happen?
a) Water will become good conductor of electricity (✓) b) Water will become bad conductor of electricity.
c) Water will neither become good conductor nor bad conductor. d) None of the above.
11. Sanjeev noted that there is layer of another metal on iron vehicles. Why is this done?
a) To prevent rusting. b) To increase the strength of iron.
c) To make the surface shiny. d) All of the above. (✓)
12. Rupinder and Noor attached one end of a LED bulb with a cell and other with a screwdriver. If screwdriver is made of iron then what will happen if it is attached to the other terminal of cell?
a) Bulb will glow(✓) b) Bulb will not glow c) Can't say anything d) Bulb will blink.
13. Robin stood near motorcycle and asked his father that the rim of wheel is made of iron but why is it more shiny then normal iron?
a) Due to more driving b) Motorcycle is new
c) There is plating of another metal on iron (✓) d) Can't say anything.
14. On passing electricity through copper sulphate solution, copper will deposits on the plate connected to which terminal of battery?
a) Positive terminal b) Negative terminal (✓) c) Both terminals d) None of the both.
15. While electroplating of copper which liquid is added to make the copper sulphate solution more conducting?
a) Sulphuric acid (✓) b) Sodium Hydroxide c) Sugar solution d) Kerosene oil
16. Out of below given options which is the use of magnetic effect of current?
a) Electroplating b) Electric Iron c) Electric Bulb d) Electric Bell (✓)
17. Rajesh's father brought a LED from market. Rajesh noted that one wire of LED is long and another is short. The Long wire is connected to which terminal of battery?
a) Positive terminal (✓) b) Negative terminal c) Neither positive nor negative d) Any terminal
18. Pari's father told her that air is bad conductor of electricity. But Pari has seen the lighting moving toward ground very fast in rainy season even though it was not raining at that time. What is then reason for this?
a) Due to low temperature b) Due to more humidity in air (✓)
c) Due to high wind speed d) All of the above
19. Some articles e.g. some parts of cars, taps and gas burners have plating of chromium on them.Among the given statements which is not correct for chromium?
1. Chromium has shine. 2. Chromium does not corrode. 3. Chromium is very cheap.
a) 1 (✓) b) 2 (✓) c) 3 d) All of the above.
20. Which object can be used instead of iron nail in given circuit so that flow of current remain uninterrupted?
a) Graphite (✓) b) Plastic c) Wood d) Rubber
21. Which statement is incorrect regarding electroplating?
1. Electroplating is the process of plating one metal on another metal.
2. It is helpful in disposal of industrial chemicals.
a) 1 (✓) b) 2 c) Both statements are correct. d) Both statements are incorrect.
22. Today teacher asked four students to bring magnetic compass from science lab. Students brought the devices according to table given below. Which student brought the right device?
a) Amanjot b) Rohini c) Meera (✓) d) Gagandeep
23. A tester is used to check the conductance of 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:
a) Liquid A is better conductor than liquid B. (✓) b) Liquid B is better conductor than liquid A.
c) Both liquids are equally conducting.
d) Conducting properties of liquids can't be compared in this manner.
24. In the below given activity two carbon roads from two waste dry cells are connected with battery and then dipped in a bowl containing water. After sometime bubbles of gases appeared around carbon rods. These bubbles are of which gases?
a) Nitrogen and Chlorine b) Oxygen and Hydrogen (✓)
c) Oxygen and carbon dioxide d) Sulphur dioxide and Oxygen
25. Prem is having electric fittings in his house, someone advised to used LEDs in place of ordinary bulb. LED is better than ordinary bulb because:
a) LED consumes less energy. b) LED is lightweight c) LED is long lasting. d) All of the above. (✓)
26. Among the substances given below which is not a good conductor of electricity?
a) Aluminum b) Mercury c) Graphite d) Distilled water (✓)
I Fill in the blanks:-
1. A Compound formed by ions is called ________ .
2. The electrode connected to the negative terminal is _________ .
3. Distilled water does not conduct _______.
4. Electroplating is an important use of _______ .
II Choose the correct option:-
1 A liquid metal that conducts electricity :-
(a) Sodium (b) Mercury (c) Lead (d) Gold
2. An atom or a radical that becomes charged is called :-
(a) Radical (b) ion (c) electrode (e) none
3. Metals are extracted from their ores by the process of :-
(a) electroplating (b) electrolysis (c) both (d) none
III Name the following:-
1. An atom that loses an electron
2. Cell used in electrolysis
3. A liquid or a moist paste that has ions in it
IV Define the following:-
1. Electrolysis.
2. Electroplating.
3. Electrolyte.
4. Electrode.
V Draw the following diagrams and label it.
1. Electroplating steel spoons with silver.
2. Flow of ions in an electrolyte.
3. Electrodes.
VI Give reasons for the following:-
1. An acid or ionic salt added to water during the electrolysis of water.
2. Water taps are coated with nickel or chromium.
VII Answer the following in not more than 20 words:-
1. Define anode and cathode.
2. Mercury is a liquid that conducts electricity. What constitutes a current through it ?
VII Answer the following in not more than 40 words :-
1. What happens when a voltage is applied across electrodes placed in an electrolyte ?
IX. Label the diagram and answer the following questions
1. Give a suitable heading to the diagram given below.
2. Name the electrode which collects hydrogen .
3. Name the electrolyte.
4. Write a chemical equation for the process given below.
Click on link below to download CBSE Class 8 Science Chemical Effects of Electric Current Assignment Set A
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