I’m still in the middle of teaching density. I just found this demo on the net and decided to try it out. This demo illustrates the effect of temperature on the density of liquids. When a liquid’s temperature increases, the density decreases. Why? Remember, density is the amount of matter in a given space (mass in a given volume). When the temperature increases, the molecules of the liquid are slightly spaced farther apart, thus the volume is slightly increased, and the density lowers as a result. The opposite occurs if the temperature decreases. The video below shows what happens when a flask of hot colored tap water is place into a larger beaker of ice water. The less dense colored water rises, like a volcano, to the surface of the higher density ice water. Over time, of course, the colored water cools, and will sink slowly into the surrounding water.
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