Written by Sarah Kellett

Life jackets are often orange to make them easy to spot after an accident. And orange fruit have their own life jackets, all built in!

You will need

  • An orange
  • Water
  • Large bucket or bowl

What to do

  1. Fill the bucket or bowl with water.
  2. Drop in the orange. Does it float?
  3. Take out the orange and remove all of the peel.
  4. Drop the orange flesh into the water. Does it still float?
  5. Try dropping a piece of peel into the water. What happens?

What’s happening?

Look carefully when you put the orange into the water and you might see the water level rise. When any object goes into water, it pushes some of the water out of the way. It’s called displacement, and you’ll also see it happening when you get into a bath. Your body displaces water, and the water level rises.

An object sinks when it weighs more than the water it displaces. The object goes down because it is heavier than the amount of water that has to go up. When you first put the orange into water, it floats because it is lighter than the amount of water that it displaces.

But take off the peel, and you’ll find the flesh of the orange is heavy, and the peel is light. Orange flesh contains water, sugar and other bits and pieces that makes it heavier than if it was just all water. Orange peel has pockets of air which makes it lighter than the water it displaces, so it floats.

Real-life science

The orange peel acts like a life jacket; it keeps the orange flesh floating when its on, but without it the orange will sink. When people go sailing, they wear life jackets so they will float better in water.

Ships use water displacement to keep afloat. Even large tankers can float because of their shape and pockets of air within the metal hull.

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