CBSE Class 8 Science Chemical Effect Of Electric Current Worksheet

1) Give some examples of good conductors and poor conductor liquids -

Good Conductor liquids                            Poor conductor liquids

.................................................... ....................................................

2) Fill in the blanks :-

i) Distilled water is _________________ of electricity.

ii) Bulb gets heated and glows due to _____________ effect of electric current

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

iv) Most liquids that conduct electricity are ________, ________ and _________.

3. Give three examples of electroplating.

i) ....................................

ii) ....................................

iii) ....................................

5. Match the column _
Column ‘A’                             Column ‘B’
a) Process of deposition of       i) Good Conductor gold or silver on ornaments
b) Carbon rod                           ii) Electrode
c) Distilled water                       iii) Poor conductor
d) Vinegar                                iv) Electro-plating.

6. Identify the following pictures and name them -

I. Write answer for the following as directly :

1. What is LED ?

2. Name a gas which burns with a pop sound.

3. Which electrode is connected to the negative terminal of a cell ?

4. Name the ions which are positively charged.

5. Name a device which is used for the electrolysis of water ?

6. Write a chemical equation for the electrolysis of water.

II Answer the following in 2 or 3 lines :

1. Define the following :

a) Electrolyte b) Cathode c) Anode d) Jons e) Voltameter

2. What is electroplating ?

3. Draw a neat diagram of voltameter and label it

4. Identify the following as electrolytes and non electrolytes :

a) dil HNo3 b) Benzene c) Petrol d) Zinc Chloride solution e) a solution of Naoh g) Ether h) Alcohol i) Common salt solution

5. State three uses of electrolysis.

III Define the following in detail :

1. Describe an experiment to show chemical effect of electric current.

2. Describe an experiment for the electroplating of an iron object with copper.

Q1. What do you understand by chemical effect of current?

Q2. Differentiate between conductors and insulators with examples.

Q3. Why distilled water isused an insulator? How can it be made a conductor?

Q4. What are electrodes? Name two elements that can be used to make electrodes.

Q5. List the various chemical effects produced when electric current is passed through a conducting solution.

Q6. What happens when electric current passes through water by keeping two electrodes immersed in it?

Q7. What is electroplating? Give its three uses.

Q8. What is the disadvantage of electroplating?

Q9. Describe an experiment to show the process of electroplating. Alsoexplain in detail why we find a coating of copper on the negative electrode.

Q10. You are given a carbon rod, a copper plate and copper sulphate solution. Explain the arrangement you will do to get a coating of copper on the carbon rod.

Q11.Give reasons for the following:

1. Chromium is used for electroplating.

2. Iron cans used for storing food items are electroplated with tin.

3. Bridges and automobiles are either painted or coated with zinc to prevent rusting. Why aren’t they electroplated?

4. We should never handle electrical appliances with wet hands.

Q12. Fill in the blanks:

1. Three effects of electric current are ___________, ___________ and _____________.

2. When current is passed through a conducting solution it causes __________________ reactions.

3. Full form of LED is ________________________. The longer lead in LED is always connected to the ____________ terminal of the battery.

4. Liquids that conduct electricity are solutions of acids, bases and __________.

5. When electric current is passed through acidulated water, the gases produced are ___________ and __________.

6. The object to be electroplated is connected to the ____________ terminal of the battery in the circuit.