S4.7.7 For the adult
Electrolysis
Carbon cannot take the oxygen from aluminium oxide. So how is aluminium made?
What this chapter teaches
Electrolysis splits a molten ionic compound with an electric current. Positive ions go to the cathode and make a metal. Negative ions go to the anode and make a non-metal. Aluminium is above carbon in the reactivity series, so its oxide is dissolved in molten cryolite and electrolysed, which uses a great deal of electricity.
Three questions to ask
There is no one right wording. Listen for the idea.
- Why must an ionic compound be molten before it can be electrolysed?
- Where does the metal form, and why does it go there?
- Why is aluminium made by electrolysis and not with carbon?
After the chapter, the learner can
- Predict the products of electrolysis of a molten ionic compound
- Explain why aluminium is extracted by electrolysis, not with carbon
What they copy into their notebook
A molten ionic compound conducts because its ions move. Positive ions go to the cathode and make a metal. Negative ions go to the anode. Aluminium needs electrolysis.