Fake Lung Experiment – Find out how lungs work

The lungs are an essential organ to all mammals. It is the organ that allows for gaseous exchange to ensure we get the enough oxygen into our bodies and also exhale the waste products. Today we’re going to find our how lungs work by making a fake lung.

What you will need

  • A plastic bottle
  • A straw
  • An elastic band
  • Scissors
  • 2 balloons
  • Play dough


1. Remove the bottom of your bottle.

2. Tie a knot in one end of a balloon and snip of the fat end.

3. Stretch this end around the bottom of your plastic bottle.

4.  Put a straw in the neck of the other balloon and secure tightly with the elastic band but not so that you crush the straw. The air must flow through, so test it with a little bow through the straw to see if the balloon inflates.

5. Put the straw and the balloon into the neck of the bottle and secure with the play dough to make a seal around the bottle – make sure that again, you don’t crush the straw.


How lungs work

Hold the bottle and pull the knot of the ballon at the bottom. What happens?

You should find that the balloon inside the bottle inflates, and that as you let go it deflates.

Why does this happen?

As the knotted ballon is pulled it creates more space inside the bottle. Air then comes down the straw and fills the balloon with some air to fill the space! When you let go of the knot the space no longer exists, so the air from the balloon is expelled making it deflate.

This demonstrates how our lungs work. Air is taken in through the mouth and nose, passes down the windpipe and into our lungs. The diaphragm at the bottom of our chest moves down to create more space. As we breathe out the diaphragm raises again. The knotted balloon represents the diaphragm and the balloon inside the container the lung.


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There are 57 comments

  1. Emily

    This is excellent, thank you. My son and I have just started exploring science at home and this site is wonderful. I’m so glad you link up to Sharing Saturday, thank you.

  2. Mama B

    I am new to your site and really like it! I pinned the how to make a lung idea to my learning ideas board – what a great idea…can be used in so many ways! Thank you!

  3. Amy

    This is a great idea! And it would work well to show the effects of smoking too. Use a wide straw (like one from McDonald’s) to fill the lung, then feel the difference in how fast or easily the lung fills using a narrow straw (like a tiny one for stirring coffee). I will for sure be doing this demo with kids! Thanks!

  4. tracey

    You have to use a very sturdy water bottle for this project. My son and I went through many balloons trying to make it fit over a standard water bottle…..we ended up using a Snapple drink bottle because the plastic is stronger.

  5. Ellie

    I’m making this for a science project and I hope that I do it right!How clever!It must have taken a while to think of that.GREAT IDEA!

  6. Becca

    Great demonstration, I just wanted to correct the following statement:

    “This demonstrates how our lungs work. Air is taken in through the mouth and nose, passes down the windpipe and into our lungs. The diaphragm at the bottom of our chest moves down dot create more space.”

    The diaphragm is the muscle that makes breathing happen. As it contracts and spreads flat in the abdomen, it creates a vacuum that draws air into the body. This model demonstrates how a vacuum works.

  7. Leila

    This is so great. I teach flute and was looking for some kind of demo – this is perfect – if I can get mine to work as well as yours does 🙂

  8. Aasiyah

    Suggestions: Instead of using a balloon as the lung, you can cut off the fingers of a doctors glove and Sellotape it to a y tube. It’s much more accurate

  9. Rose

    It can be difficult to find plastic bottles that hold up to having a balloon stretched across the bottom. They all seem too thin. Can anyone suggest brands?

  10. jess

    This s a great experiment, we did it with 10 year olds and really got them thinking – easy and clear – thanks for the clear instructions 🙂
    Just in case you want to know – few spelilng errors noticed – of not off and ballon and bow not blow.. x

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