Caution
• Do not taste the copper chloride solution. • Do not inhale the gas it gives off – it is poisonous. • Wash your hands after the experiment.
METHOD Step 1 Put the two carbon rods in the copper chloride solution. Keep them separate as shown in Figure 8.
Step 2 Record any observations. Step 3 Connect up the circuit, as shown. Make sure that the two rods do not touch. The rod connected to the negative side of the battery becomes the negative rod and the rod connected to the positive sides becomes the positive.
Step 4 Observe the carbon rods carefully.
negative side of battery
negative carbon rod
copper metal (Cu)
solution CuCl2 Figure 8 Set up the experiment like this
RESULTS 1 Observe and record what happens at the negative carbon rod. 2 Observe and record what happens at the positive carbon rod. Could you smell anything?
3 Suggest the substance produced at each electrode. Think about what was in the beaker to start with.
4 Draw a diagram of the apparatus to record the results of this experiment.
CONCLUSION 1 Write a conclusion from this experiment about the effect of electric current on chemical compounds.
2 State where the energy used to break up the compound comes from. 3 Describe the changes you think happened in the copper chloride solution.
The process of electrolysis
In Activity 4, the copper chloride solution was split into its elements copper and chlorine, by an electric current. The current is conducted between two electrodes. These are carbon rods that carry the electric current to and from the solution.
The electrical current caused a chemical reaction that broke down the compound into ions of its elements. Copper ions have a positive charge and chlorine ions have a negative charge. The copper ions were attracted to the negative carbon rod (opposite charges attract each other). Copper metal was deposited on the rod. Chlorine ions were attracted to the positive carbon rod. Chlorine gas was given off.
positive side of battery
copper wire
positive carbon rod
chlorine gas (Cl2
)
Unit 3 Effects of an electric current 117
STRAND 3
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