Investigating air pressure – more eggs!

Today we are looking at air pressure. Air pressure is the force exerted by air on any surface in contact with it.

We are going to demonstrate air pressure by using it to force an egg into a bottle.

What you need:

A boiled egg

A glass bottle or jar with a neck a little smaller than an egg

2 matches

What to do:

  • Place the cooled boiled egg on top of the glass bottle, making sure there is no way the egg fits through.

air pressure

  • Ask an adult to light two matches and drop them inside the glass jar, quickly place the egg back on top.
  • Watch as the egg drops inside the jar.

Ignore the carrot in our jar, we didn’t have any matches so had to fashion a carrot and some cocktail sticks!

The Science Bit

The matches heat up the air inside the glass jar. The air then expands and some escapes out of the jar. Once the matches go out, the air starts to cool, making the pressure drop. The air outside the jar now has a higher pressure than the inside, and forces its way inside the jar, forcing the egg downwards as it does so.

Our jar was quite small, so it would be interesting to see what would happen if a larger one was used. If you try please let us know!

Pop back over next week to see how to make a barometer to measure air pressure.

 

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There are 29 comments

  1. maggy, red ted art

    Ooh very clever… does take me back to science days.. I would have tipped on that there is “less air” in the jar once the fire has “consumed it”… thus lower pressure. Need to scrubbed up my physics. Makes me have a good think again!

    Thank you for linking to kids (&mums) get crafty!

    Maggy

  2. Kayren

    with a larger jar it should suck the egg down into the bottom of it- did this with my kids in 8th grade science class and it never ceases to amaze them (me too)

  3. Andy

    To get the egg out all you need to do is create a higher pressure inside the container. This can be done by holding it upside down and blowing air into it. Since it’s upside down the egg will act as a plug when you stop blowing. With the higher pressure inside of the container now, the egg should pop out.

  4. joyce

    we did this with a balloon filled with water – eggs are a bit too precious over here – and it worked beautifully

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