You’ll need

  • Water
  • A tall, clear plastic cup (or glass)
  • Food colouring
  • Liquid honey (not creamed honey)
  • Vegetable oil
  • Several small objects, such as a paperclip, a marble and a toothpick

What to do

  1. Gather your materials on a flat surface.
  2. Pour some water into the cup so it is around one-quarter full.
  3. Add a few drops of food colouring to your water.
  4. Pour the same amount of honey into the cup. Wait for the liquids to stop moving. Does the honey sit above or below the water?
  5. Pour the same amount of oil into the cup. Again, wait for the liquids to stop moving. Where does the oil sit?
  6. Before you drop your small objects in, make a guess about what will happen to them. Now drop them in.

Questions to ask

Where did your small objects end up when you dropped them into your liquid sandwich? Were your guesses right?

What happens if you drop a fizzy tablet, such as an Aspro Clear, into the water? Where does it settle? How do the bubbles travel through the different liquids?

Can you make a 7-layer liquid sandwich? Try using – in order – honey, golden syrup (or corn syrup), liquid soap, water, vegetable oil, methylated sprits and lamp oil (also known a liquid paraffin; kerosene will do). You may need to use a pipette (like a large eye-dropper) and put each liquid in slowly.

Some of these liquids are highly flammable! The 7-layer version needs adult supervision!

What's happening

The liquids make different layers because they have different densities. An object’s density is how much mass a given volume of that object has, or how tightly packed the material that makes up the object is. If you have the same volume of 2 different liquids, like oil and honey, the denser liquid will weigh more. You could check this by weighing a cup each of honey and oil.

Of the 3 layers, honey is the most dense. It sits at the bottom of the cup. The next layer is water. Oil is less dense than both honey and water, so it sits at the top. If a small object that you drop into the cup is less dense than the fluid it displaces (or pushes out of the way), the object will float. If it is more dense than oil and water but less dense than honey, where do you think it will stop sinking?

You can learn more about the science of floating and sinking by doing the activity – Experimenting with floating and sinking.

Did you know

The concept of different liquid layers is often seen in fancy drinks! A tropical sunrise is a drink with 2 layers. It has orange juice on top of red grenadine syrup to create a beautiful sunrise effect.