This project was ridiculously simple. No mess, took seconds to set up, and was tons of fun. Not to mention it provided the perfect background for a discussion on density.
- A glass, jar, or bottle (preferably one with a lid...we used a spaghetti sauce jar)
- Vegetable oil
- Food coloring
The instructions are simple! Fill your jar about 3/4 full of vegetable oil. Then fill the rest of the way with water. Leave a little room at the top of the jar though, you don't want it overflowing. (Notice how the water sinks to the bottom while the oil floats on top.)
Add about 10-12 drops of food coloring and stir. (It only colors the water. Hmmmm....) You want your water to be fairly dark in color so you can really see what's about to happen.
Wait just a minute for the mixture to settle back down from all that stirring. Cut your Alka-Seltzer tablets into smaller pieces (like 6 or so) and drop in one piece at a time. Then, sit back and watch the magic...er...science happen!
So, how does this work?
We all know that oil doesn't mix with water. Water is heavier (more dense), which explains why it sinks to the bottom of the jar. This also explains why the food coloring only mixes with the water. Their densities are similar and their molecules are much more friendly with each other :)
When you add the Alka-Seltzer, this causes little carbon dioxide bubbles to form. These bubbles attach themselves to the colored water, making them float up to the top of the jar. When they pop, the little blobs of water float back down. Voila!
Note: Once you used up all of your Alka-Seltzer and all the bubbling has settled down, tightly screw your lid on the jar and tilt from side to side. The oil and water combo makes a neat wave motion that just might keep your little scientist entertained for a few more minutes!