Page 2 - CBW
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8.     Assertion (A): LED does not glow in a circuit made with distilled water.
                    Reason (R): Distilled water lacks free ions to conduct electricity.

             9.     Free ions, not electrons, are responsible for conduction of electric current in liquids. Justify
                    the statement.
             10.    Ravi observed that the iron nails in his toolbox were rusting over time. His teacher explained
                    to him about electroplating and how it is used to coat metals with another metal to prevent
                    corrosion and improve appearance. She demonstrated how a silver layer could be coated on
                    a copper spoon using a silver salt solution and electric current.


                    Based on the case study, answer the following questions
                       a)  What is the process of depositing a layer of metal using electricity called?
                       b)  Which terminal is the copper spoon connected to during electroplating?
                       c)  Why is electroplating done on iron objects?
                       d)  What is the role of the electrolyte in electroplating?

             11.    Meena tested 4 different liquids: Tap water, lemon juice, salt solution, and distilled water
                    using an electric circuit and an LED. She found that the LED glowed for all except distilled
                    water. She concluded that not all liquids conduct electricity.

                    Based on the case study, answer the following questions.
                       a)  Why didn't the LED glow in case of distilled water?
                       b)  Which property of lemon juice allows it to conduct electricity?
                       c)  What does the glowing of LED indicate in this experiment?
                       d)  What type of liquids are good conductors of electricity?



             12.                                       A few drops of sulphuric acid is added to water before it
                                                      is electrolysed.

                                                      What is the role of sulphuric acid in the above activity.








             13.    To detect the presence of electric current in a circuit containing a weak
                    electrolyte, we prefer to use a LED.


                    Why are LEDs more efficient than common bulbs?


             14.
                                                     Some metals can get corroded after some time. They look
                                                     gorgeous when they are electroplated. Iron is such a metal
                                                     that can be electroplated to prevent rusting.

                                                     a) Name a metal that can be used to electroplate Iron.
                                                     b) Can we use the same metal to electroplate Iron?
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