.
Materials
Tray, goggles, two infusion
bottles 50 mL with stopper pierced by two tubes,
drinking straw, lime water.
Experiment
1. Prepare the stopper like seen in Fig. a and
b.
2. Pour 20 mL of lime water into two 50-ml
infusion bottles.
3. Close the right bottle by stopper pierced by
two tubings: The longer one dips into lime water, the shorter one is for inhaling
of air.
4. Inhale by sucking one long breath of
fresh air through the short green tubing.
5. After that exhale this air through
a drinking straw into the lime water of the left bottle.
Observation (Fig.
b)
The exhaled air makes lime water (left bottle)
milky while inhaled does not change it (right bottle).
Explanation
Lime water is a reagent
for the gas carbon dioxide that was formed in the body cells by chemical
reaction of air with nutrients.