Page 4 - HA 3

4. Take some freshly prepared lime water in another test tube.

5. Use a syringe or pichkari to pass air through that test tube.

6. Again, note the time taken for this lime water to turn milky.

Observation:
When we blow air through mouth it turns lime water milky instantaneously. While
when we blow air through syringe or pichkari, it takes a lot of time and effort to turn
the lime water milky.

Explanation:
Our body cells produce carbon dioxide through oxidation of food. This gas is exhaled
outside through the lungs. Lime water reacts with CO 2 to form an insoluble
precipitate. This turns lime water milky.
Ca(OH) 2(aq) + CO 2(g) ——–> CaCO 3(s)
(Lime) (Insoluble Precipitate)

When syringe or pichkari is used, atmospheric air is pushed through the lime water.
Atmospheric air contains very less amount of CO 2. As a result lime water does not
turn milky or takes a lot of effort.

Inference:
This experiment demonstrates that our lung exhales more amount of carbon dioxide
than the amount of CO2 present in the atmosphere.

Activity Work Sheet- 4