Chemical effects of electric current sslc

Useful for students of grade 10

1. Chemical effects of electric current

2. What are conductors and insulators?? Conductors are the materials which allow electric current to pass through them they are also called good conductors Insulators are the materials which do not allow electric current to pass through them they are also called poor conductors.

3. Do liquids conduct electricity?? Liquids conduct electricity Most of the conducting liquids are either acids bases or salt solutions Electricity in liquids is carried by ions. .When electricity is passed through liquids chemical changes takes place.

4. Activity 1 Take a container or a beaker Add one teaspoon of lemon juice or vinegar. Dip the free ends of the tester into this container Conclusion When the liquids between two ends of the tester allows electric current to pass the circuit of the tester becomes complete Current flows through the circuit and the bulb glows

5. Led is used to detect weak current in the circuit. One end of LED is slightly longer than the other Longer LED of the LED is always connected to the positive terminal Shorter end of the LED is always connected to the negative terminal.

6. Activity 2 Take a tray from a discarded Matchbox . Wrap an electric wire a few times around the tray Place a small compass needle inside it Now connect one free ends of the wire to the terminals of the battery Repeat the activity with different solutions like tap water vegetable oil etc

7. Activity 3 Take about two teaspoons of distilled water in a clean and dry container Use the tester to test whether distilled water conducts electricity or not Note down your observation Dissolve A pinch of common salt in distilled water Test again.

8. Conclusion Distilled water is free of salts and hence a poor conductor of electricity. Tap water contains dissolved solved salts and hence a good conductor of electricity.

9. Activity 4 Take two leads of pencil We call these leads as electrodes. The rod connected to positive terminal is called anode and one which is connected to the negative terminal is called cathode. Connect the free ends of the electrodes to the terminals of the battery through connecting wires. Immerse the electrodes in a solution of water. Add a teaspoon of salt to make it more conducting. Wait for 3 to 4 minutes Observe the electrodes carefully

10. Conclusion Passing an electric current through a conducting solution causes chemical reaction Gas may be formed. Change in the colour. Change in the odour. Change in the temperature.

11. Activity 5 Cut a potato into two half an insert copper wires of the tester into it Leave it undisturbed for 2 to 3 hours. Conclusion Greenish blue spot on the potato around one wire. Colour change is seen on the terminal connected to the positive end of the battery.

12. Electroplating Activity -6 Take two copper plates Take 250 ml of distilled water in a clean and dry beaker Dissolve two teaspoons of copper sulphate in it Add a few drops of dilute sulphuric acid to make it more conducting. Connect the copper plates to the terminals of the battery and immerse it in copper sulphate solution. Allow the current to pass for 15 minutes Remove the electrodes and observe them carefully

13. Conclusion Copper sulphate dissociates into copper and sulphate ions. Free copper ions get attracted to the electrode connected to the negative terminal of the battery and gets deposited on it From another electrode an equal amount of copper gets a dissolved in the solution. The loss of copper from the solution is a restored and the process continuous. Hence copper gets transferred from one electrode to the other.

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

15. Applications of electroplating Chromium plating is done on many objects such as car parts bath tab kitchen burners bicycle handle bars, wheel rim and many objects. Chromium has a shiny appearance and does not corrode. Jewellery makers electroplate silver and gold on less expensive metals. These ornaments have the appearance of silver or gold but are less expensive. Tin cans used for storing food are made by electroplating tin on iron Iron is used in making bridges and automobiles to provide strength, since iron corrodes a layer of zinc is deposited to protect it from corrosion