This demonstration uses balloons, straws, and a plastic bottle to create a working model of the lungs and diaphragm. Pulling on the bottom balloon increases the chest cavity volume, causing the lung balloons to inflate, while releasing it decreases the volume, causing them to deflate.

1. Cut the bottom off a 2-liter plastic bottle to form the chest cavity.
2. Make a Y-shaped straw connector: cut one straw to create legs for the “Y,” then attach it airtight to another straw with a diamond-shaped opening.
3. Attach a balloon to each end of the Y-shaped connector to act as lungs, securing them with tape or elastic bands.
4. Place the straw and balloon structure inside the bottle and thread the straw through the bottle’s neck. Seal the opening airtight with tape or plasticine.
5. Tie a knot in a third balloon, cut across its widest part, and stretch it tightly over the bottom opening of the bottle, taping in place. This acts as the diaphragm.
6. To operate, gently pull down on the knotted balloon to simulate inhalation and release it to simulate exhalation.

DIY model lungs - MEL Chemistry:

Respiration: Lung model in a bottle - QEST Inc:

📄 Build a model lung - Inverness Science Festival: https://www.uhi.ac.uk/en/t4-media/one-web/university/stem/isf/fayre-22/make-a-lung.pdf

• Use transparent balloons for the lungs so inflation is more visible.
• Try different bottle sizes to model different chest cavity volumes.
• Connect multiple straws and balloons to model additional branching bronchi.

• Use scissors carefully when cutting the bottle and straws.
• Supervise children with balloons, as broken pieces can pose a choking hazard.
• Ensure all seals are tight to avoid frustration if the model doesn’t work initially.

• What happens when the diaphragm balloon is pulled downward? (The chest cavity volume increases, lowering air pressure and drawing air into the lung balloons.)
• What happens when the diaphragm balloon is released? (The chest cavity volume decreases, pushing air out of the lung balloons.)
• What part of the body does the bottle represent? (The chest cavity.)
• Why do the lungs inflate and deflate without being squeezed directly? (Air pressure changes inside the cavity cause the balloons to expand and contract.)