Directions: Making a Lava Lamp (pdf - 18kb)

The Science behind this activity: Oil and water do not mix. They have different densities. Oil is less dense (less heavy) than water. Even if you try to really shake-up the bottle, the oil breaks up into small little drops, but the oil doesn't mix with the water. Food coloring only mixes with water. That's why it does not color the oil. In addition, the Alka-Seltzer reacted with the water to make tiny bubbles of carbon dioxide gas. These bubbles attached themselves to the blobs of colored water and cause them to float to the surface. When the bubbles popped, the color blobs sank back to the bottom of the bottle.