Breathing and Diseases of Lungs and Airways

June 28, 2009

Breathing: Inhaled and Exhaled Air

Filed under: breathing system — Tags: , , , , , , — 11:27 am

One way to find out what happens when we breathe is to compare the air which we inhale with the air which we exhale. If there are any differences, these should give us a clue about what happens to the air inside us and why we need it.

  • Move your hand gently backwards and forwards in the air in front of you. This shows you what ordinary inhaled air feels like.
  • Hold your hand a few centimetres in front of your open mouth. Breathe out against it as if trying to whisper the word ‘hah’. You should be able to feel two differences between ordinary (inhaled) air and exhaled air. One of these differences is even easier to see if you breathe onto a mirror.
  • Collect a sample of exhaled air in a gas jar or similar container.
  • Use an identical container for a sample of ordinary air.
  • Find out how long a candle burns in the jar of ordinary air. Then see how long it burns in exhaled air.

After all the difference is pretty obvious. But why do we breathe? What do we need air for? When we eat plants (or animals that have eaten plants), the energy they contain passes into us. Oxygen is used by the body to help to break down the energy-containing foods. This releases the energy in them. This energy is used for many things including moving around/ keeping the heart beating and the body warm. Without oxygen there is no energy, and these vital processes will stop. The body must get enough oxygen. It must also get rid of carbon dioxide because this is poisonous if too much stays in the body. The next activity follows the route taken by oxygen and carbon dioxide as they pass into or out of the body.

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