Kitchen Density Layers

No adult supervision needed: only food-cupboard ingredients are used. Wipe up spills straight away because oil and honey make floors slippery, and note that food colouring can stain.

Protective equipment and “do not substitute” warnings have not been recorded for this experiment yet. They are added when its safety review is completed; until then, follow the supervision notes above.

Disposal: Do not pour oil down the sink: soak it up with kitchen paper and put it in general waste. The honey and water can go down the sink with running water.

Materials

• A tall clear plastic cup
• Runny honey
• Water with a drop of food colouring
• Olive oil or another cooking oil
• A spoon

Steps

1. Pour honey into the cup until it is about a quarter full.
2. Hold the spoon upside down just above the honey and slowly pour the coloured water over the back of the spoon so it runs gently down the side.
3. Do the same with the oil.
4. Look at the cup from the side and draw the layers.
5. Stir the top two layers together, then watch for a minute.

What you should see

• Three separate layers form: honey at the bottom, coloured water in the middle and oil on top.
• After stirring, the oil breaks into drops that rise back up and form a layer on top of the water again.

Why it works

Density is mass divided by volume: how much matter is packed into a given space. A liquid that is less dense than the liquid around it floats on it, and a denser one sinks.

Olive oil has a density of about 0.92 g/cm³ and water about 1.00 g/cm³, so the oil floats on the water. The honey sinking to the bottom shows that it is denser than water. Oil and water also do not mix (they are immiscible), so even after stirring they separate again into layers.

Learn the ideas behind it

• Molecules
• States of Matter

Sources

• College Physics 2e, 11.2 Density — OpenStax
• College Physics 2e, 11.7 Archimedes' Principle — OpenStax
• Chemistry 2e, 11.3 Solubility — OpenStax