• A clean 1-litre clear soda bottle
• 3/4 cup of water
• Vegetable oil
• Fizzing tablets (such as Alka Seltzer)
• Food colouring
What to do:
1. Pour the water into the bottle.
2. Use a measuring cup or funnel to slowly pour the vegetable oil into the bottle until it’s almost full. You may have to wait a few minutes for the oil and water to separate.
3. Add 10 drops of food colouring to the bottle. (We like red, but any colour will look great.) The drops will pass through the oil and then mix with the water below.
4. Break an Alka Seltzer tablet in half, and drop the half tablet into the bottle. Watch it sink to the bottom, and let the blobby greatness begin!
5. To keep the effect going, just add another piece of the tablet. For a true lava lamp effect, shine a flashlight through the bottom of the bottle.
How does it work?
The oil stays above the water because oil is less dense than water. The oil and water do not mix because of something called intermolecular polarity — a term that is fun to bring up during dinner conversations. Intermolecular polarity means that water molecules are attracted to other water molecules. They get along fine and can loosely bond together, forming drops. This is similar to the action of magnets that are attracted to each other. Similarly, oil molecules are attracted to other oil molecules. The structure of the water and oil molecules does not allow them to bond with each other. Of course, there’s a lot more fancy scientific language to describe density and intermolecular polarity, but maybe now, you’ll at least look at that vinaigrette salad dressing in a whole new way.
When you added the piece of tablet, it sank to the bottom and started dissolving and creating a gas. As the gas bubbles rose, they took some of the coloured water with them. When the blob of water reached the top, the gas escaped and down went the water. Cool, huh? By the way, you can store your “Blobs in a Bottle“ by putting the cap on the bottle. Then whenever you want to bring it back to life, just add another piece of the tablet.