Why does lava rise in a lava lamp

Home Archives About Contact. Media Player Error Update your browser or Flash plugin. Density Whether something sinks or rises in water is determined by its density. Hot And Cold When you turn on the bulb in the lamp's base, that heats the wax enough so that it starts to rise. Become an Indiana Public Media supporter. Sign-Up Here. The whirling globs we remember are made mainly of paraffin wax, with compounds like carbon tetrachloride added to increase its density.

Ada McVean B. The Science of Basil 11 Sep How do you know? Washing your hair? Ask an adult for help disposing of it. Options may include putting it in a sealed container in the trash or pouring it outside. This activity brought to you in partnership with Science Buddies. Follow him on Twitter BenFinio. Already a subscriber? Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options. Go Paperless with Digital.

Materials Clear glass Tap water Vegetable or mineral oil Food coloring Alka—Seltzer tablets Flashlight optional Preparation Prepare a work area where you can easily clean up any spills, such as a kitchen counter. Procedure Fill your glass about one quarter full with water. Add several drops of food coloring. Fill the rest of the glass with oil not all the way to the brim. Break an Alka—Seltzer tablet into four roughly equal-size pieces.

Drop one of the pieces into the glass. What happens? Oil floats on water because a drop of oil is lighter than a drop of water the same size. Another way of saying this is to say that water is denser than oil. Density is a measurement of how much a given volume of something weighs. Things that are less dense than water will float in water. Things that are more dense than water will sink. 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. 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. This looks like a Lava Lite.