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 less oxygen and more carbon dioxide.
C Contains no oxygen and only carbon dioxide.
D Contains more nitrogen and less water vapour.
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Worked Solution

Step 1: In the lungs, oxygen is absorbed into the blood and carbon dioxide is released from the blood. Step 2: Exhaled air will have less oxygen (used by the body) and more carbon dioxide (waste product). Step 3: It also contains more water vapour and is warmer.

Correct answer: Contains less oxygen and more carbon dioxide.

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