Would it just turn into a pressurized container full of steam? Would the water stay water but just like, really hot?
In: 98
The boiling point of water changes with the pressure. This book has a phase diagram for water you can look at for a visual (Figure 2b): [https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Physical_Properties_of_Matter/States_of_Matter/Phase_Transitions/Phase_Diagrams](https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Physical_Properties_of_Matter/States_of_Matter/Phase_Transitions/Phase_Diagrams)
You can see from that diagram that at 1 atm (regular atmospheric pressure) the boiling point of water is 373 K (which is 100 C, or 212 F). If you put the water in a sealed container and increased the temperature, the pressure inside would increase as some of the water turned to vapor. Since it can’t all turn to vapor, the pressure would rise along with the temperature following that curve.
What is happening physically is that the water molecules in the liquid move around more quickly as the temperature increases, eventually leaving the liquid because their kinetic energy is higher than the potential energy holding them together. If the container were open, they would escape as steam. However, in a closed container, they can’t escape, so they run into the walls of the container, exerting a force on it before bouncing off and going back into the liquid. If you could see inside, you would see something that looks kind of like boiling but much more chaotic. The pressure would continue to rise with the temperature until the force exerted on the walls by the water vapor became greater than the forces holding the walls together, at which point the vessel would explode and release all of that energy at once.
This is an extremely dangerous thing when it happens, and can easily destroy buildings or kill people. [Large boiler explosions](https://en.wikipedia.org/wiki/Boiler_explosion) have destroyed ships and leveled city blocks, killing hundreds of people.
As a result, all pressure vessels have safety valves that release gas when the internal pressure gets too high. When those fail, it is a serious safety hazard. The water heater in your house can contain enough pressure that if it were to explode, it would destroy your home and potentially your neighbor’s home as well.
Even breaches that aren’t explosions but just vent steam from a pressurized pipe or vessel are extremely dangerous. The leaks are invisible, extremely hot, and can cut through people.
All of this is to say, don’t try to do this yourself!
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