Mixing oil and water with detergent is a fun way to explore basic chemistry with kids. This science experiment is suitable for kids over 4 years of age. You don’t need any special equipment… in fact I am sure you already have everything you need in the kitchen cupboards. It can be a little messy so I suggest attempting the experiment outside or somewhere that is easy to clean. When my kids and I are playing with science I like to ask them lots of questions and listen to their answers – they come up with some very imaginative responses. But if you are interested in the facts I have included further explanation for what is happening at the end of the post.
Oil, Water & Detergent Experiment
You will need:
- Glass jam jars (with lids if you want to shake them)
- Jug of water
- Vegetable oil
- Food colouring
- Small container
- Syringes or droppers
- A cloth for accidental spills
- Optional: Table salt
1. Pour one cup of water into your glass jam jar.
2. Pour half a cup of vegetable oil on top of the water in the jar.
3. Stop and observe. Does the oil mix with the water? Screw the lid onto the jar and shake it…. can you get the oil and water to mix?
4. Mix a generous squirt of detergent with some food colouring in a separate small container.
5. Using a dropper or a syringe squirt some coloured detergent into your oil and water filled jar.
6. Watch what happens….. you should see a lava lamp like affect with bubbles of colour falling through the mixture.
Repeat this progress as many times as you like.
7. If you would like to see a different reaction try pouring a teaspoon of salt into the mixture and watch what happens.
So, what is happening?
There are a lot of interesting things to note during this experiment. Firstly oil and water do not mix. Even if you shake the jar the oil will immediately separate from the water as soon as it settles. Oil molecules are attracted to other oil molecules so they stick together. The same goes for water molecules….. so they just don’t mix.
The oil always floats on top of the water because the oil has a lower density than water.
Detergent is different again. It is attracted to both water and oil molecules. Detergent grabs onto both types of molecules causing oil droplets to be suspended in the water. When you shake the jar the detergent molecules adhere the water and oil together forming an emulsion. An emulsion is a substance of molecules who are not normally attracted. That is why detergent is so useful for cleaning greasy dishes!
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