Exhaled air and lime water
It has more carbon dioxide.
Is breath the same?
The air we breathe out is not exactly the air we breathe in.
How could we find out if exhaled air has more carbon dioxide?
What this lesson covers
The idea
Exhaled air contains more carbon dioxide than inhaled air, though not all the oxygen in inhaled air is used up.
Is breath the same?
The air we breathe out is not exactly the air we breathe in.
How could we find out if exhaled air has more carbon dioxide?
- Use lime water, which turns milky with carbon dioxide
- Look at the air with our eyes
- Smell the air
Lime water test
A teacher passes ordinary air into tube A and blows breath into tube B. Press the two buttons and watch the lime water.
B turned milky
Lime water turns milky when it reacts with carbon dioxide. B turned milky and A did not. Not all the oxygen of the inhaled air is used up, so some oxygen is breathed out as well.
Exhaled air contains more carbon dioxide than inhaled air, though not all the oxygen in inhaled air is used up.
Notes
Exhaled air contains more carbon dioxide than inhaled air, though not all the oxygen in inhaled air is used up.
Check yourself
What turns lime water milky?
Tube B got our breath and turned milky. Tube A got ordinary air and did not. What does this show?
Is all the oxygen of the inhaled air used up in the body?
Which air has more carbon dioxide?
- Carbon dioxide — correct. Yes!
- Oxygen. Lime water turns milky with carbon dioxide, not with oxygen.
- Sugar. Lime water turns milky when it reacts with carbon dioxide.
- Exhaled air has no carbon dioxide. B turned milky, so exhaled air has carbon dioxide.
- Exhaled air has more carbon dioxide than inhaled air — correct. Yes!
- Inhaled air has more carbon dioxide. A did not turn milky. It is exhaled air that has more carbon dioxide.
- Yes, all of it. Not all the oxygen is used up. Some of it is breathed out.
- No oxygen is used at all. The body does use oxygen, but not all of it is used up.
- No, some oxygen is breathed out — correct. Yes!
- The air we breathe out — correct. Yes!
- The air we breathe in. The air we breathe in has less carbon dioxide than the air we breathe out.
- Both have exactly the same amount. Exhaled air has more carbon dioxide than inhaled air.