Breath Composition
Biology: Edexcel IGCSE, topic 3.2.9
Breath Composition
The air that is breathed in is different to the air breathed out. The amount of carbon dioxide in our breath can be tested using a solution called lime water.
Differences
- Some of the oxygen that is breathed in is used up in respiration, and the carbon dioxide produced in respiration is breathed out.
- So air that is breathed out contains less oxygen but more carbon dioxide than air breathed in.
- The air that is breathed out also has more water vapour in it because the airways are moist inside.
Investigate
- Lime water is a clear solution that turns cloudy when carbon dioxide dissolves in it.
- An experiment where air that has passed through lime water is breathed in (so the carbon dioxide in the air is not breathed in) and exhaled air passes through lime water and turns it cloudy shows that more carbon dioxide is breathed out.
Test yourself on Breath Composition
What solution can be used to test the amount of carbon dioxide in our breath?
How does the air that we breathe out compare to the air that we breathe in?
What are the differences between air that is breathed in and air that is breathed out?