The Little Tinkerer

Lava Lamp Polarity demonstration

What you’ll need:

• one large plastic bottle (like a soda bottle)
• ¾ cup vegetable oil
• ¼ cup water
• food coloring
• Alka-Seltzer tablet

What to do:

• Pour the water into the bottom of the bottle
• Pour the oil in on top, and wait a few minutes for the water and oil to separate
• Add some drops of food coloring until the water gets darkly colored
• Break the Alka-Seltzer tablet in to a couple of pieces, and drop one of the pieces into the water
• Watch what happens to the bubbles as the tablet dissolves
• Tip: shine a light through the bottom of the bottle to make it look even more like a lava lamp!

How it works:

Water is a polar molecule, which means it has an uneven charge distribution within the molecule. This means it doesn’t mix or interact with vegetable oil, which is a nonpolar molecule. This concept is best summarized as ‘like dissolves like’

Notice that the food coloring only mixes with the water, which tells us that the food coloring molecules must also be polar.

When you add the Alka-Seltzer, it begins to release carbon dioxide bubbles which attach to the water blobs that have formed in the bottle and causes them to float to the top. This is what creates the colored bubble effect in the lava lamp!