What You'll Need
- 3/4 litre vegetable oil
- 1/4 litre water in a jug
- Food colouring
- Alka Seltzer or fizzy Vitamin C tablet
- Litre plastic or glass bottle or a clean jam jar
How to Do It
- 1Pour the water into the bottle or jar ¼ up
- 2Add about 10 drop of food colouring to colour the water.
- 3Carefully fill the remaining jar with the vegetable oil. If you tilt the bottle as your filling it with the oil less bubbles will form. Allow the oil and water to settle until it is completely clear.
- 4Break up the Alka-Seltzer tablet into four pieces.
- 5Now for the Magic:
Drop one of the pieces of the Alka-Seltzer into the oil and water mixture.
Watch what happens, the tablet will sink to the bottom of the bottle. Then it starts to dissolve and create a gas which appears fizzy. This gas forces the coloured water up through the oil. When the bubbling stops, add another piece Alka-Seltzer. It’s just like a lava lamp!
Oil and water do not mix.
Oil stays above the water because oil is lighter then water which is also know as less dense then water. Oil and water not mixing is called “Intermolecular polarity”. (this is the big fancy pants word of the day).
The molecules of water do not like to mix with the molecules of oil. Even if you try to shake up the bottle, the oil breaks up into small little drops, but the oil doesn’t mix with the water. Also, food colouring only mixes with water. It does not colour the oil.
Alka-Seltzer tablet reacts with the water to make tiny bubbles of gas which is known as carbon dioxide. These bubbles attach themselves to the coloured water and that is what causes them to float to the surface. When tiny bubbles pop, the carbon dioxide escapes from the coloured water. Because the coloured water is heavier than the oil it then drops back to the bottom of the bottle.