Page 29 - ICSE Science 3 : E-book

What to Do:
• With the help of an elder, cut the bottom of the soft-
drink bottle using scissors.

• Fix the two small balloons using rubber bands at the
openings of the Y-shaped glass tube or a hose connector.
• Insert the tube into the mouth of the bottle. Fix it tightly
using the tape.

• Take the large balloon and tie a knot at its end. Then cut
it half horizontally using scissors.
• Now fi x the open end of the half balloon with knot over the wide bottom of the
bottle. Tighten it using a large rubber band. This acts as the diaphragm of your lung
model.

• Tie a string to the knot of the balloon.
• Gently pull down the string and then release it.
Observe what happens to the two small balloons within your lung model.

Observation:

On pulling down the string, the two balloons inside the bottle expand as air fl ows into
them. But when the string is released, the balloons contract. This is because the air within
the balloons is expelled out.

Result:
The purpose of making this lung model is to show what happens when we breathe in

and out.
During inhalation, the diaphragm contracts (moves downwards) and air enters the
lungs. As a result, lungs expand and get fi lled with air. During exhalation, the diaphragm
expands (move upwards) and air is expelled which causes lungs to contract.

Based on the above activity, match the following things with the organs they
represent in a human respiratory system.
Column A Column B

1. A Y-shaped glass tube or a hose connector (a) Chest cavity and
ribcage
2. A large balloon that covers the bottom (b) Lungs
of the bottle

3. A two-litre empty soft drink bottle (c) Diaphragm
4. Two small balloons attached to the glass tube (d) Windpipe

15