I’ve been watching this videos on YouTube of people boiling water in vacuums. Pretty interesting and I understand the basics. Kind of lol. When the atmospheric pressure is equal or less than the liquid pushing up it’ll turn into a gas but my question is.
How come I can’t see the vapor like when I’m boiling water in a pot? Also since it was a closed vessel that the guy was making the vacuum in when the water turns to gas doesn’t that make the pressure go up in the vessel? Thanks for any insight or food for thought!
In: Chemistry
The vapor you see when boiling a pot isn’t the water vapor, its water that has condensed back into tiny droplets. Water vapor is invisible/clear. Edit for the why: Traditional boiling happens in an air filled room. That air is much cooler than the freshly boiled vapor and cools it. The air can only hold limited water and the vapor is a lot of water, so it condenses out of the air into tiny droplets, creating the steam cloud you see. In a vacuum chamber there is no* air and the water doesn’t convert to vapor by heating. So it cooling down doesn’t cause a phase transition back to a liquid and it remains gas.
Yes, as the water boils in the vacuum chamber the vapor will increase the pressure. But they leave the pump running in demonstrations so the vapor is pumped out keeping the pressure low enough to maintain the boil.
*Its not a true vacuum, just a greatly reduced amount of air. Vacuum chambers still contain some gas.
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