Have you ever heard the saying ‘oil and water don’t mix’? Well, today Lahiru and Malinthi are going to demonstrate that this is absolutely true – and sometimes, very beautiful to look at. I love this experiment, and the way the different coloured food dyes start off making an ugly brown mess in the oil before separating out like upside-down fireworks!
Dr Lahiru Gangoda is a cancer researcher and a member of Team WEHI. Her research is on finding better ways to treat skin cancer. Don’t forget wear your sun screen! You can read more about Lahiru here.
Malinthi is in grade 6. She loves science and looking after the environment. She is the Science captain and the Green-house vice-captain at her school. Malinthi is also part of the space-wattle team at her school. Her school will be receiving some Golden Wattle seeds (Australia’s national floral emblem) that has been on board the International Space station for the last 6 months. The space-wattle team will plant and looks after these seeds that has spent time in space.
*Science is great fun! But please, always check with an adult before you start your experiment!*
You will need:
- A tall clear glass of water
- A small glass of oil
- Food colouring in several colours
- A spoon or fork for stirring!
Step 1:
Put a few drops of each colour of food colouring into the oil
Step 2:
Mix the food colouring with the oil (it will not mix completely, but it will break down into smaller droplets of colouring)
Step 3:
Carefully pour the oil into the water.
Step 4:
Watch what happens!
Malinthi will now demonstrate this experiment for you!
What can we learn?
Food colouring is water based, so it dissolves in water, but it doesn’t dissolve in oil. If you mix oil and food colouring together, you will see a lot of tiny particles of food colouring stuck in the oil.
Oil is lighter than water, so when you add the oil to the water, the oil will sit in a layer on top.
However, food colouring is denser (and heavier) than oil, and so bit by bit the particles of food colouring that were mixed with the oil will escape, and sink to the bottom of the oil layer, where they meet the water and start to colour it.
Oil and Water in the Kitchen: Have you ever helped your parents make a salad? When you whisk together oil and vinegar for a dressing, it works much the same way as the oil and food colouring did here – if you beat it very quickly, you can make the droplets of vinegar that are mixed with the oil really, really tiny, until the dressing looks like it is all one colour and texture (this is called an emulsion). But if you leave the salad dressing to sit for a few minutes, the oil and vinegar will separate into two layers again – just like the food colouring separated from the oil in this experiment.
Team WEHI Relay for Life 