Standard Science Primary 5 Systems

Which of the following correctly describes the air we breathe out compared to the air we breathe in?

A Contains more oxygen and less carbon dioxide.
B Contains more carbon dioxide and more water vapour.
C Contains less oxygen and less nitrogen.
D Contains more nitrogen and less water vapour.
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Worked Solution

Step 1: Breathing in brings oxygen into the lungs. Step [2-9]: The body uses oxygen and produces carbon dioxide as waste. Step [2-9]: Exhaled air thus contains more carbon dioxide and moisture picked up from the lungs.

Correct answer: Contains more carbon dioxide and more water vapour.

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