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Questions

1. The liquid in the flasks is called lime water. At the beginning of the experiment it is clear. What does the lime water indicate if it:

2. If you breathed through this apparatus for a few minutes what would you expect to see happening in Flask A and Flask B?

3. Which of the two flasks has inspired air passing through it?

4. What does this experiment tell us about inspired air compared with expired air?

A good test for oxygen is to try to burn a candle in a sample of of an unknown gas. Oxygen is a gas which supports combustion (burning). If a candle is put into a gas jar containing pure oxygen it will burn for many minutes very brightly. The following experiment was carried out to test the combustion of the air breathed in and out by a man.
To gas jars were taken. Air from the atmosphere was trapped in one and air exhaled from a man's lungs was collected in the other.

Atmospheric air

The candle burns for 30 seconds in A
The candle burns for 4 seconds in B

5. What do these results tell us about the amount of oxygen in the two jars?

6. What does our body do to the air that we breathe in and out? (Explain the difference in the percentage of gases in inhaled and exhaled air).