Kids, did you ever want to try to make your own lava lamp? While real lava lamps rely on materials and chemicals for a more advanced age group, you can get a similar effect with simple household ingredients. Here is what you need: vegetable oil or baby oil, water, food coloring, glitter or small beads, and a glass jar with a lid. First, fill the jar about a third full of oil. Next, sprinkle on glitter, sequins, small beads, or any tiny sparklies that catch your eye. Add water to nearly fill the jar and add a drop or so of food coloring. Finish filling the jar with water, then screw the lid on tightly. Flip the jar over. Flip it back. Shake it up. Have fun!
Please note: All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.
What's going on? The oil is less dense than water, so it wants to float on top. Water is a polar molecule, while oil is nonpolar. Polar molecules stick to each other, but not to nonpolar molecules. Even though oil and water are both liquids, they are what chemists call immiscible liquids. That's a fancy word that means they don't mix. When you add the food coloring, is it in the oil or the water? How can you tell? Is food coloring polar or nonpolar?
Try this variation. Let the liquids settle then open the jar and sprinkle a tiny bit of salt on top. What happens? Why? Salt is heavier than water, so when you pour salt on the oil, it sinks to the bottom of the mixture, carrying a blob of oil with it. In the water, the salt starts to dissolve. As it dissolves, the salt releases the oil, which floats back up to the top of the water.
How does a lava lamp work? Like your oil and water, the "lava" doesn't mix with the liquid that surrounds it. When it's cool, the lava is a little more dense than the liquid surrounding it. When the lava rests on the bottom, the light bulb in the lamp warms it up. As it warms up, the lava expands a little. When it expands, the lava stays the same weight but it takes up more space, which means that it is less dense. When it's warm enough, the lava rises up to the top to float. At the top of the lamp, it cools down, becomes more dense, and sinks once again. This cycle repeats over and over as the lava warms up and rises, then cools down and sinks.
A traditional lava lamp consists of a conical metal base with a 40-watt light bulb, and a teardrop-shaped glass container that fits snugly over the base and bulb. Inside this glass container is a combination of colored water or alcohol and a gooey substance consisting mostly of paraffin wax, carbon tetrachloride and mineral oil. There is also a little science lesson about emulsions and specific gravities in each lava lamp, but above all they offer us some fun!
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Kathleen Carrado Gregar, PhD, Argonne National Labs
[email protected]
January 2006
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Reference:
Dr. Anne Marie Helmenstine at http://chemistry.about.com/cs/howtos/ht/nontoxlavalamp.htm
and Michael Pollick at http://www.wisegeek.com/what-is-a-lava-lamp.htm.
Eric Muller at http://www.oozinggoo.com/howto.html gives the original patent as well as typical homemade mineral oil/alcohol versions.
