Can you boil water without heat? Why and how does it occur?
As usual, I will start with the short answer: Yes.
Now to the details. Boiling is the spontaneous change of water from the liquid phase to the gas phase. However, as is true for all materials, temperature is not the only parameter that determines the phase; there is also pressure that affects its phase. Thus, every material has a "phase diagram", with temperature and pressure as its coordinates.
Although water has some strange behaviour at the liquid-solid boundary, the liquid-gas boundary is quite standard. The boiling point drops with decreasing pressure. The familiar 100°C (212°F) is the boiling point of water at 1 atmospheric pressure (i.e., the mean pressure at sea level). When the pressure drops, the boiling point drops as well.
So, if you want to boil water, you have two options:
1. Add heat until the temperature reaches the boiling point at the fixed pressure.
2. Reduce pressure (e.g. by vacuuming the container water is in) until the boiling point at that pressure drops below the fixed temperature.
So, if you would rather not heat your water, you can lower the pressure around it. Then it will boil, but of course it does not mean that it is "hot"! Obviously not a way to cook your spaghetti.
Yasar Safkan, Ph.D., Software Engineer, GVZ., Istanbul, Turkey
'The strength and weakness of physicists is that we believe in what we can measure. And if we can't measure it, then we say it probably doesn't exist. And that closes us off to an enormous amount of phenomena that we may not be able to measure because they only happened once. For example, the Big Bang. ... That's one reason why they scoffed at higher dimensions for so many years. Now we realize that there's no alternative... '