4 ms·

Why the boiling?

• spectre 16y ago
  As pressure decreases boiling point also decreases, so in a vacuum it is below your body temperature. http://en.wikipedia.org/wiki/Atmospheric_pressure#Boiling_point_of_water http://en.wikipedia.org/wiki/Atmospheric_pressure#Boiling_po...
• fowlerrr 16y ago
  If I can remember my high school physics, basically it's because of the low pressure. Pressure x Volume = Temperature, so as the pressure decreases, so does the temperature. But Wikipedia answers it better than I can: http://en.wikipedia.org/wiki/Boiling_point http://en.wikipedia.org/wiki/Boiling_point
  • jjs 16y ago
    You're looking for the Ideal Gas Law (http://en.wikipedia.org/wiki/Ideal_gas_law http://en.wikipedia.org/wiki/Ideal_gas_law), which is derived from Boyle's Law (relation between gas pressure and volume), and Charles's Law (expansion of gas when heated). The related concept here is that liquids remain liquid when the vapor pressure of the substance is less than the atmospheric pressure. So, by the above laws, you can make water boil by (a) heating the water to increase the vapor pressure, or (b) reducing the atmospheric pressure to less than the existing vapor pressure of the water, or (c) some combination of (a) and (b).
• mmaunder 16y ago
  Get a syringe. Fill it about a quarter way with water. Turn it facing up and squirt out any air bubbles. Block the end where the needle goes with your finger. Pull the plunger back hard as if you're filling it all the way up. You'll pull a hard vacuum and you'll see the water inside bubble as it boils at room temp.
  • ovi256 16y ago
    Used to do that each time I had a syringe available. Such fun.
• by 16y ago
  In a gas the molecules are moving around with lots of space between them without much interaction. Some quickly, some slowly, all in different directions. Occasionally they collide and bounce off each other, or more rarely they may temporarily form weak (liquid) bonds with each other until a fast molecule hits them and breaks them apart. In a liquid the molecules (which are indistinguishable from gas molecules of course if you looked at them individually) are moving much slower and form and re-form weak (liquid) bonds with the molecules near them. But still there are some moving faster and others more slowly and they are going in random directions. Now think about the surface where the liquid meets the gas. There are some gas molecules that plunge into the liquid and become part of the liquid and there are some liquid molecules moving fast enough to escape from the liquid, breaking all their weak (liquid) bonds, and become part of the gas. The liquid surface at a molecular scale will not be a nice flat surface. It will be a complex seething bubbling thing with droplets and molecules leaving and rejoining the liquid. If we heat the liquid, make the molecules move faster, more of them will be moving fast enough to escape from the liquid. Anyway, if there are more molecules going from the gas to the liquid we say the gas is condensing, and if there are more going the other way the liquid is evaporating. Now think what would happen if we take away all the gas molecules - put the liquid into a vacuum. There will no molecules returning to the liquid, only liquid molecules becoming gas. Conversely, if we compressed the gas above the liquid we would get more gas molecules going into the liquid. I think that's how it works.
  • knieveltech 16y ago
    Straight out of Feynman's lectures. Well said.
• elblanco 16y ago
  It's due to the low pressure. Like with these guys. http://www.acenovelty.com/donace/coffeepen06.jpg http://www.acenovelty.com/donace/coffeepen06.jpg