Density Dan’s “Groovy” Lava Lamp


To observe that all liquids do not mix together in a "groovy" fun way


  • Empty, clean plastic soda bottle
  • Vegetable oil (any kind, any price)
  • Water
  •  Food coloring
  •  Alka-Seltzer tablet or fizzy antacid tablets


Fill the bottle 3/4 full with vegetable oil. Fill the rest of the bottle with water (almost to the top but not overflowing). Add about ten drops of food coloring. Notice that the food coloring only colors the water and not the oil. Divide the antacid tablet into eight pieces. Drop one of the small pieces into the oil and water mixture. Watch what happens. When the bubbling stops, add another chunk of antacid.


You’ve just made a version of a groovy lava lamp! The molecules of water do not like to mix with the molecules of oil. Even if you try to shake up the bottle, the oil breaks up into small little drops, but the oil doesn’t mix with the water. Also, food coloring only mixes with water. It does not color the oil. When you pour the water into the bottle with the oil, the water sinks to the bottom and the oil floats to the top. Oil floats on the surface because water is heavier than oil. Scientists say that the water is more dense than the oil. The antacid tablet reacts with the water to make tiny bubbles of carbon dioxide gas. These bubbles attach themselves to the blobs of colored water and cause them to float to the surface. When the bubbles pop, the color blobs sink back to the bottom of the bottle.