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J. Perelman
"Entertaining physics". Book 2.
Chapter 7. Thermal phenomena


"If boiling water is not suitable for this purpose, what to talk about snow!" - will answer some readers. Do not hurry with the answer, and do better experience at least with the same glass bottle that you just ate.

Fill it with water up to half and cook in boiling salted water. When the water in the bottle boil, remove it from the pan and quickly seal prepared with a tight closure. Now turn the bottle and wait until boiling inside him will stop.

After this time, pour the bottle with boiling water, the water will not boil. But put on his bottom a little snow or even just pour cold water, as shown in the picture, and you will see that the water boils... Snow did what the could not do the boiling water!

The boiling water in the flask, oblivious cold water.

This is all the more mysterious that touch the bottle is not particularly hot. Meanwhile you own eyes see how the water is boiling!

The clue is in the fact that the snow cooled walls of the bottle; as a consequence, the steam inside the condensed water drops. As well as the air from the glass vial was even expelled by boiling, the water is exposed to much less pressure. But it is known that reducing the pressure on the liquid, it boils at a temperature lower. We have, therefore, in our bottle though and boiling water, but boiling water. unheated.

If the walls of the bottle is very thin, the sudden condensation of vapor inside it can cause a sort of explosion; the pressure of the external air, without sufficient opposition from within the bottle, able to crush it (you see, incidentally, that the word "explosion" is inappropriate here). It is better to take so round flask (flask with a rounded bottom), so that the air is pressed on the vault.

Just safer to produce a similar experience with a tin Cup for kerosene, oil, etc., Schipachev it a little water, screw tight tube and pour the dishes with cold water. Immediately tin of steam will slyshitsja pressure of external air as the steam inside will turn when cooled in water. The tin will be wrinkled by the pressure of the air as it struck the heavy hammer.

An unexpected result of the cooling of the cans.

Entertaining physics J. Perelman


System Orphus


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