Method:

What you have to do:: 1) Fill the plastic bottle about three quarters full with cooking oil

.2) Top up with water. The water is considerably denser than the oil, so it should flow to the bottom of the bottle.

3) Add approximately 10 drops of food colouring to the bottle. The colouring has the same density as the water, so will sink through the oil and enter the water.

4) Add half an Alka-Seltzer tablet to the bottle.

5) Observe.

Result: The food colouring mixes with the water and bubbles up through the oil and then falls back down in droplet form.

Conclusion: The Alka-Seltzer tablet reacts with the water and creates carbon dioxide. The carbon dioxide particles latch on to the water making it rise through the oil in drops. The bubbles of carbon dioxide burst when they reach the surface of the oil and their payload - the drops of coloured water - fall back through the oil because water is denser than the oil. The cycle continues as long as the Alka-Seltzer tablet is working.

Warning - Health and Safety: Do not put the cap on the bottle during this experiment. Carbon dioxide is produced by the Alka-Seltzer tablet and the bottle may burst.

Sixth Class Experiments