EquipmentPlastic bottleScissors‘Gaffer tape’Elastic band/ ThreadTube (straw)Plastic bagBalloon

Method1. Remove the label from the bottle by filling the bottle with hot water to

melt the glue then peel off the label. This will enable you to view the inside of the bottle clearer.

2. Cut the base of the bottle using scissors. N.B. cut away from yourself for safety reasons.

3. Fasten a balloon to a tube using an elastic band or piece of thread.4. Put the balloon inside the bottleneck and put the lips of the balloon back

over the bottle head.5. Insert the plastic sheet inside the bottle but make sure that the edges

remain just outside the bottle.6. Use gaffer tape to create a seal so no air can get between the plastic and

the circumference of the bottle.

ObservationsAs the plastic sheet, representing the diaphragm, is pulled down the balloon expands however when the plastic sheet is pushed up the balloon contracts. The expansion is as a result of a larger volume in the bottle, which reduces the pressure, and therefore air is drawn in the balloon in the same way that air is drawn into the lungs. The opposite happens when the plastic pushes up as it causes the pressure to increase causing air to be forced out the lungs or in this case balloon.

Part of model Part of real body Similarities Differences

Plastic bottle Rib cage/ Thorax Capacity can be changed from diaphragm movement.

Bottle doesn’t have intercostal muscle so cant expand.

Balloon Lungs Inflate when the diaphragm pushes down.

There are 2 lungs with millions of alveoli but only 1 balloon.

Plastic sheet Diaphragm Creates a partial vacuum.

Movement of diaphragm is an involuntary action

Tube into the bottle Trachea Connects the lungs to the air

Doesn’t have ciliated epithelium so doesn’t produce mucus.