Did you know that lava lamps don't actually contain any lava? lava lamps are essentially just wax and water. There are two things that make these substances unique: They have very close densities and they are insoluble between one another. the density of water is 1000kg/m^3. Insoluble means that the two substances don't mix. Water and oil are examples of insoluble substances.in lava lamps, there is a light bulb at the bottom of the glass container. the light bulb heats up the wax at the bottom. wax has a melting point of 115o F. when the wax changes from solid to liquid, the molecules begin to move apart from each other. The density changes from over 1000kg/m^3 to under 1000kg/m^3. this means that when the wax reaches a certain temperature, it begins to float. when the wax is at the top of the glass container, it begins to cool off. when the wax cools off, the molecules come back together, the wax solidifies, and the wax sinks. this constant cycle of sinking and floating wax is what creates the random flowing of liquids in a lava lamp.