What it shows
Oil and water do not mix, but some kitchen ingredients called emulsifiers surround the tiny oil drops and keep them spread in the water. You shake the oil and water with different ingredients and time how long they take to separate.
The science
The molecules in an emulsifier have one end that likes water and another that likes oil. They sit on the surface of each oil droplet and stop the droplets from joining back together. Without an emulsifier the oil drops merge and rise to the top quickly, because oil is lighter than water.
Materials
Cost: under Rs 50. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- 6 small identical clear jars with lids
- Cooking oil
- Water
- Mustard, honey, a drop of dish soap, milk and plain curd
- A teaspoon and a stopwatch
- A marker
- A ruler
Safety
For this project: Do not taste the jars, especially the one with dish soap. Wash the jars well afterwards, and keep them away from small children.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
All the safety rulesStep by step
7 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Pour three spoons of water and three of oil into each of the six jars.
Leave jar 1 as it is, and add a spoon of mustard to jar 2, honey to jar 3, a drop of dish soap to jar 4, milk to jar 5 and curd to jar 6.
Close the lids tight and shake each jar for exactly thirty seconds.
Place the jars in a row and start the stopwatch.
Look at each jar every minute and note when a clear oil layer first forms.
Measure the thickness of the oil layer at ten minutes with a ruler.
Rank the ingredients from best to worst emulsifier.
What you should see
Plain jar separates in under a minute, while jars with mustard, milk or soap stay milky much longer. The ranking tells you which ingredient is the best emulsifier.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1What is an emulsion?
A mixture of tiny drops of one liquid spread in another that normally would not mix.
2What does an emulsifier do?
It coats the drops and stops them from joining together.
3Why does oil float on water?
Oil is less dense than water.
4Name a food that is an emulsion.
Mayonnaise, milk or butter.
Take it further
Make a salad dressing with the best emulsifier and test how long it stays mixed in the fridge.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
Free ebooks for this project
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