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An egg with a green yolk in a bowl

Prank your friends with a green egg!

Time for an Easter trick! There are lots of eggs around at this time of year, but this one is sure to raise some eyebrows. And when you’re finished, you can get your parents to help you cook your green egg, so you can gross out your entire family!

food safety hazard iconSafety: Use clean hands and clean equipment when handling food. Ask an adult to help cook eggs.

You will need

  • 2 bowls
  • Fresh eggs
  • Empty plastic bottle
  • Fork
  • Green food dye

What to do

Someone is holding a plastic bottle over a cracked egg.

Gently touch the bottle to the yolk

  1. Crack an egg into one of the bowls.
  2. Grab the plastic bottle.

The next part is a bit tricky and might take some practice!

  1. Squeeze the bottle gently.
  2. Carefully touch the egg yolk with the mouth of the bottle. Be careful not to break the yolk!
    There's a yolk in a plastic bottle.

    Release the bottle and the yolk will be sucked up!

  3. Release the squeeze on the bottle. The yolk should be sucked into the bottle.
  4. Pour the egg yolk into the other bowl.
  5. Add a few drops of green food dye to the egg white and stir gently with the fork.
  6. Using the same method as before, take the yolk out of the second bowl and place it back into the centre of the egg white. You now have a green egg!
    Someone is stirring a green liquid.

    Add some green food colouring to the egg white

  7. Ask an adult to help you cook the egg, just like a normal egg. Make sure everyone is watching when you eat your green eggs!

What’s happening?

You were able to suck the egg yolk into the bottle thanks to the difference in pressure created between the inside and outside of the bottle.

An empty bottle actually has something in it – air! Air is made up of tiny particles. The force of all these particles pushing on an object is called air pressure. And, air pressure changes depending on how tightly packed the air particles are.

If a large amount of air is forced into a small container, the air particles won’t have much room to move about, putting high pressure on the walls of the container. In a larger container, the same amount of air particles has more room to spread out, reducing the pressure on the walls of the container.

When you squeezed the bottle, you forced some air out and created a smaller volume inside it. By releasing the squeeze on the bottle, the volume increased. This created a pressure difference, where the air pressure inside the bottle became lower than the air pressure outside the bottle. The higher pressure outside the bottle then forced air (and the egg yolk) inside the bottle!

Real-life science

A difference in pressure causes something that we experience every day: wind!

Air is warmed by the Sun, which gives the air particles more energy and makes them spread out. Wind is created as the warm air (low pressure) rises into the atmosphere, causing colder air (high pressure) to move in and replace it.

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