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J. Perelman
"Entertaining physics". Book 1.
Chapter 6. Thermal phenomena


Take a test tube, fill with water, immerse the piece of ice, and that he should not come up (the ice is lighter than water), push its lead bullet, copper weight, and so on; however, the water must have free access to the ice. Now move the tube to the spirit bulb so that the flames licked only the upper part of the tube. Soon the water begins to boil, releasing clouds of steam. But the strange thing: the ice on the bottom of the tube does not melt! We have in front of you like a small miracle: the ice is not melting in boiling water...

Water in the upper part of boils, meanwhile, the ice does not melt below.

The answer lies in the fact that at the bottom of the tube the water is not boiling, but remains cold ; it boils only at the top. We are not a “ice in boiling water”and “ice under the boiling water”. Extending from the heat, the water becomes lighter and does not fall to the bottom and remains in the upper part of the tube. Currents of warm water and mixing layers will occur only in the upper part of the tube and is flush with the lower more dense layers. The heat can be passed down only by conduction, but the thermal conductivity of water is extremely small.

Entertaining physics J. Perelman


System Orphus


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