GRADE 7- BIOLOGY

To show that exhaled air has less oxygen and more carbon dioxide:

This activity was performed with the help of two student volunteers. Two candles were lighted and kept. Air was blown into a glass jar for a minute. Both the glass jars were then upturned over the lighted candles at the same time. The time taken for each candle to extinguish was noted down.

The candle covered by the glass jar into which air was blown, extinguished faster than the other candle. This showed that exhaled air contained carbon dioxide, as it did not support combustion.