Summative Practice (Question 3 & 4) – Form 5 Science (KSSM) Chapter 6


Question 3:
Rohani found a rusted iron nail. Using your knowledge of electrolysis, describe a simple way to prevent the rusting of the iron nail.

Answer:
The rusting of the iron nail can be avoided by electroplating the iron nail with copper through electrolysis under the following conditions:

• iron nail is made the cathode

• pure copper is made the anode

• copper(II) sulphate solution is used as the electrolyte

• electric current is supplied by an electrical source to carry out the electrolysis


Question 4:
You are given three potatoes, three iron nails, three copper rods, light bulb and connecting wires with crocodile clips. Using these materials, design a simple chemical cell with the following features:
(a) simple chemical cell that can light up a light bulb with maximum brightness.
(b) simple chemical cell that can last the longest when lighting up a light bulb.

Answer:
(a)
Three simple chemical cells, each made up of a potato with an iron nail and a copper rod poked into the potato and connected in series as in the figure below.


(b)
Three simple chemical cells, each made up of a potato with an iron nail and a copper rod poked into the potato and connected in parallel.

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