# Lava Lamp Density

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In the lamp you have two liquids which are: * Very close in density * Insoluble in one another Oil and water are insoluble in one another (that's where the expression "oil and water don't mix" comes from), but oil and water have very different densities (a volume of water weighs a lot more than the same volume of oil). They won't work, so you search to find two liquids that are very close in density and are insoluble. This site can help you in that search. (Alka Seltzer will substitute for heat ) Now you apply heat to the bottom of the mixture. In a liquid motion lamp, the heat usually comes from a light bulb. The heavier liquid absorbs the heat, and as it heats up, it expands. As it expands it becomes less dense. Because the liquids have very similar densities, the formerly heavier liquid is suddenly lighter than the other liquid, so it rises. As it rises, it cools, making it denser and therefore heavier, so it sinks. This all happens in slow motion because heat absorption and dissipation are fairly slow processes, and the density changes we are discussing here are very slight. To create the floating blobs, the two compounds in a motion lamp must be immiscible, or mutually insoluble. All this means is that liquid A doesn't dissolve in liquid B -- the two don't mix, so you see two separate liquids, one floating on top of or within the other. The classic example of immiscible compounds is oil and water. If you fill a jar with common mineral oil and water, you'll get a water layer with a layer of oil floating above it. This combination of water and oil in a jar has a similar look to a commercial motion lamp with its light turned off; in a cold lamp you see two separate layers. The coolest thing about motion lamps, of course, is that they produce distinct amorphous blobs that rise and fall in the lamp's "globe" on their own. To produce this