LA LA LAVVVVAA
For a quick and easy activity, I highly recommend lava lamps! I did this over the summer at Boys' and Girls' Club, and it was a huge hit! The kids were able to take their lava lamps home along with a few alkaline seltzer tablets to prolong the fun!
Estimated time: 20-30 minutes
Materials
Mason jars
Alka-Seltzer tablets (lots of them)
vegetable oil
food dye
glitter
water
Directions
1. Fill the mason jar a third of the way with water. Add a few drops of food dye of the desired color. Mix.
2. Fill the remainder of the jar with vegetable oil, leaving a few inches of room at the top to avoid spillage.
3. For an optional element of fun, add some glitter!
4. Split an Alka-Seltzer tablet in half, and drop it in. Watch as the lava lamp magic begins!
Science
I did a lesson on density for this project. I asked the kids to tell me which they thought was more dense before we started--water or oil. After taking a poll, we started our project. Once we realized that water was more dense, I explained:
Density is the measurement of how compact a substance is - how much of it fits in a certain amount of space. (The scientific equation is density = mass/volume.) If you measure an equal volume of oil and water, you'll find that the water is heavier than the same amount of oil. This is because water molecules are packed more tightly and a cup of water actually has more mass than a cup of oil. Because water is more dense than oil, it will sink to the bottom when the two are put in the same container.
So how does our lava lamp work?
The alka-seltzer reacts with the water to produce carbon dioxide gas bubbles. These stick to the water droplets. The water/gas combo is less dense than the oil, so they rise to the top of the flask. At the top, the gas bubbles pop and escape into the air, allowing the dense water to sink back to the bottom again.
Lessons Learned
Make sure to bring a lot of extra Alka-Seltzer tablets so the kids can bring them home. You can find them at the dollar store or any drug store. Don't let the kids mix too many colors without warning them that it'll probably turn a brownish black. The color that looks best in contrast with the yellow vegetable oil is a blueish/green.
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