Question

Design an experiment to prove that exhaled air is rich in carbon dioxide.

Answer 1

Use the mouse, or tap the screen, to reveal the results. The air we breathe in contains about 0.04% carbon dioxide. The air we breathe out contains about 4% carbon dioxide. In other words, exhaled air contains about 100 times the concentration of carbon dioxide that inhaled air does.

Answer 2

Close end of B. Breathe in. Air from atmosphere enters through A, passes through limewater and enters your mouth (cannot enter through B because closed).

Open end of B and close end of A. Breathe out. Exhaled air passes through limewater in test tube B and exits through B.

Limewater in test tube B (which contained the air you exhaled) turns milky much faster than in test tube A (which contained the air you inhaled).