Making Lava Lamps

At STEM Club we investigated Alka-Seltzer Powered Lava Lamps and how long it took the tablet to disappear, how vigorous the bubbles were, and the differences in how the reaction happened in the colder liquid versus in the hotter liquid.

The ingredients in Alka-Seltzer combine with water to form a gas called carbon dioxide. The oil and Alka-Seltzer do not combine in this way though. The Alka-Seltzer tablets sink through the vegetable oil until they reach the layer of coloured water. There the Alka-Seltzer dissolves in the water and forms carbon dioxide. The gas is lighter than the water and oil, so it bubbles up, taking a bit of coloured water with it as it moves through the oil layer. You will see those bubbles, looking like colourful blobs, floating through the oil layer to the top of the jar. At the top the bubbles should have burst (releasing the carbon dioxide gas), and then the colourful blobs sank back to the bottom (now without carbon dioxide gas). The effect was reminiscent of a lava lamp.

Click on this video link to find out more.

The chemical reaction that causes the carbon dioxide to form happens more quickly in warmer water. For this reason, the Alka-Seltzer tablet dissolved more quickly in the hot water. This resulted in lots of rapid bubbling and an energetic lava lamp display. In contrast, the Alka-Seltzer tablet in the cold water dissolved more slowly, with most of it disappearing in the first two to three minutes, resulting in a calmer and longer lasting lava lamp effect!

Mr James Bonney, Head of Design & Technology