What’s happening?

Water and oil aren’t exactly the best of friends. Because of their shape and the way their atoms stick together, they prefer keeping to themselves rather than mixing with one another. The Greek root for water is ‘hydro’, so we say that water is ‘hydrophilic’ (loves water) while oil is ‘hydrophobic’ (afraid of water). Because a drop of water has more mass than the same sized drop of oil, gravity pulls on it with more force, pulling it to the bottom.
’Fizzing’ tablets contain a mix of chemicals, including sodium bicarbonate and citric acid. Nothing happens when they’re added to oil, but when added to a solvent like water, the sodium bicarbonate separates and reforms with the citric acid to form sodium citrate. In the process, it also creates some carbon dioxide gas and a few water molecules. In your jar, the tablets reacted once they had sunk down into the water at the bottom, where they created bubbles that trapped and carried drops of water up through the oil to create your lava-like eruption.

Applications

Different chemicals need different solvents to dissolve. Some chemicals dissolve in water, but others dissolve in oil or fat.
Your body is over 70 per cent water. You also have plenty of fat (which is chemically similar to oils) – it forms the lining of every cell, and is held in large amounts in special tissue called ‘adipose’.
Vitamins such as Vitamin B and C are water soluable – they dissolve in the water in your body, and can be removed quickly from your body with urine. They need to be replaced fairly regularly to maintain good health.
On the other hand, vitamins like A, D, E and K are fat soluable, so can stick around inside your body for much longer. This might seem like a good thing, however it can lead to these chemicals building up to toxic levels if you take too much of them.
Vitamin supplements can be handy if you’re malnourished or have certain medical conditions. However, by slowly storing away some vitamins in your fat over a long period, you could be doing more harm than good. Nothing beats a well-balanced diet full of fruit and vegetables to grow up strong and healthy.

You will need

• Bottle of vegetable oil
• Glass jar
• Water
• Food colouring
• Aspro Clear, Alka-seltzer, or another kind of fizzing tablet

What to do

1. Pour water into the jar until it is 1/5th full.
2. Add several drops of food colouring to the water to stain it.
3. Fill the remainder of the jar with vegetable oil.
4. Wait about five minutes for the oil and water to separate completely.
5. Drop an Aspro Clear or Alka-seltzer tablet into the bottle and see what happens.

	You’ll need these materials.
	Add some water to the bottom of the jar and add colouring.
	Fill the remainder up with oil.
	Drop in your fizzy tablet and watch!