Make Your Own Bubbling Lava Lamp Learn how to make an inexpensive science toy. email to friend
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• 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 10 drops of food coloring. Be sure to make the water fairly dark in color. Notice that the food coloring only colors the water and not the oil. Hmmm?
• Divide the Alka-Seltzer tablet into 8 pieces.
• Drop one of the tiny pieces of Alka-Seltzer into the oil and water mixture. Watch what happens. When the bubbling stops, add another chunk of Alka-Seltzer. It’s just like a lava lamp!
  
• When you have used up all of the Alka-Seltzer and the bubbling has completely stopped, screw on the soda bottle cap. Tip the bottle back and forth and watch the wave appear. The tiny droplets of liquid join together to make one big lava-like blob.

How does it work?

First of all, you confirmed what you already knew... oil and water do not mix. The molecules of water do not like to mix with the molecules of oil. 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.

When you poured the water into the soda bottle with the oil, the water sank to the bottom. That’s because water is heavier than oil. Scientists say that the water is more dense than the oil. If oil from a ship spills in the ocean, the oil floats on top of the water.

Here’s the surprising part... The Alka-Seltzer tablet 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. Now that’s a burst of color!