Make your lava lamp. Oil is hydrophobic – it will not mix with water – even if you try to shake the bottle. The Alka-Seltzer® tablet reacts with the water to make tiny bubbles of carbon dioxide lighter than water. They attach themselves to the blobs of colored water, causing them to float to the surface. When the bubbles pop, the colored blobs sink back to the bottom of the bottle.
- Empty water bottle
- A large bottle of vegetable oil
- Food coloring
- Alka-Seltzer® tablets (with adult supervision)
- A flashlight
Fill the empty bottle ¾ full with vegetable oil.
Top it off with water and about 10 drops of food coloring.
Break an Alka-Seltzer® tablet into pieces, and add pieces of the tablet to the bottle. The mixture will bubble.
Put the cap on and gently tip the bottle back and forth. This will cause the tiny droplets of colored water moving around inside the oil to join together, making bigger blobs. Do not shake the bottle.
Shine a flashlight into the bottle from underneath, illuminating the bubbles.