Class 8 - Chemistry - Case Study Based Questions - #class8Science #cbseClass8 #eduvictors

Class 8 - Chemistry - Case Study-Based Questions

Chapter: Chemical Effects of Current

Directions: Read the following and answer the questions given below:

Case Study

Take out carbon rods carefully from two discarded cells. Clean their metal caps with sandpaper. Wrap copper wires around the metal caps of the carton rods to form electrodes and join them to a battery, Pour a cupful of water into a glass/plastic bowl. Add a teaspoonful of salt or a few drops of lemon juice to water to make it more conducting. Now immerse the electrodes in this solution. Make sure that the metal caps of the carbon rods are outside the water. Wait for 3-4 minutes, Observe the electrodes carefully.

Q(i) Which of the following is not a chemical effect of electric current?

(a) Bubbles of a gas may be formed on the electrodes.

(b) Deposits of metal may be seen on the electrodes.

(c) An electric bulb connected to the circuit may start glowing.

(d) Changes in the colour of solutions may occur.

Q(ii) Gas bubbles of ___________will be evolved near the electrodes in the given experiment.

(a) Oxygen and Hydrogen

(b) Carbon dioxide and Hydrogen

(c) Oxygen and Carbon dioxide

(d) None of these

Q(iii) A tester is used to check the conduction of electricity through two liquids, 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 a better conductor than liquid B.

(b) liquid B is a better conductor than liquid A.

(c) both liquids are equally conducting.

(d) conducting properties of liquid cannot be compared in this manner.

Q(iv) Why do we clean the metal caps with sandpaper before using them?

(a) to make the metal caps smooth

(b) to make the metal cops appear bright and shiny

(c) to make the metal caps insulating

(d) to make the metal caps free of any rust

Answers

i.  (a) gas bubbles may be formed on the electrodes.

ii. (a) Oxygen and Hydrogen

iii.(a) liquid A is a better conductor than liquid B.

iv. (d) to make the metal caps free of any rust

See Also:

Ch 14 - Chemical Effects of Electric Current (NCERT Solutions)
Ch 14 - Chemical Effects of Electric Current (MCQs)
Ch 14 - Chemical Effects of Electric Current (Q & A)
Ch 14 - Chemical Effects of Electric Current (Worksheet)
Ch 14 - Chemical Effects of Electric Current (Worksheet-2)

CBSE All In One NCERT Based Science Class 8 2022-23 Edition