Question

Yeast, warm water and substance Z were put into a test-tube. The apparatus was then set up as
shown. After a while, the lime water began to go cloudy.

What is substance Z?
A alcohol
B carbon dioxide
C glucose
D oxygen

Answer 1

The substance Z will be C. glucose.

• Yeast converts glucose to alcohol in order to gain energy.
• Carbon dioxide is released as a by product of this reaction.
• This reaction is referred to as fermentation.
• The occurrence of this reaction is confirmed by the presence of lime water going cloudy as carbon dioxide turns limewater cloudy.
• Hence, we know that the substance Z is glucose.