On Thursday 9th January, a group of Senior I students made a simple lava lamp using readily available everyday
A half litre plastic bottle was filled with approximately 200ml of coloured water. 250ml of oil were then
added to the water. Since oil is less dense than water, it settled on the surface of the water. Two distinct liquid
layers could be noted.
The students were then provided with half an Alka-Seltzer tablet. This table was inserted in
the water bottle. The Alka-Seltzer tablet reacted with the water to produce carbon dioxide gas bubbles. These stuck
to the water droplets. The water/gas combination rose to the top of the flask since it is less dense than the oil. On
reaching the top, the gas bubbles popped and escaped into the air, allowing the (dense) water to sink back to the
bottom. A circulating current was observed.