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!
Think of the radiator and cooling system in most cars – you can use plain old water in your car’s cooling system, and the pressure allows it to be higher than boiling and can carry more heat to the radiator. (Antifreeze is used because it has a higher boiling point and lower freezing point than plain water, so it’s more effective for cooling and safer in the winter since frozen water expands and can break things, and there’s anti-corrosion agents and I assume it’s a better lubricant for the water pump?)
Not a scientist but that’s how I understand what’s going on, and why if you open the cap on a hot radiator, you get a pretty dangerous, explosive release of steam and boiling coolant due to the sudden release of pressure allowing the liquid to suddenly expand.
You’d get what is called a BLEVE (blev-E)! Boiling liquid expanding vapor *explosion*. The pressure builds and builds until the container fails or ruptures. There are a lot of crazy firefighting videos about them.
Fun fact – to make soda they have to raise the temperature way higher than it should be to dissolve enough sugar into the water/ other liquids through this and other methods
As the water starts to boil and release steam the pressure in the container increases. With higher pressure the boiling point of water increases. Basically the container would increase in pressure and the liquid water content would become lower and lower until the container cannot hold the pressure and you get an explosion(assuming that you continue to apply heat).
Finding the pressure, vapour to liquid ratio etc. is a common exercise in introductory thermodynamics.
This is the application of a phase diagram.
Wiki is nice enough to show a simple example of water (in reality, solid water is super complex, consisting of multiple types of ice depending on conditions, but we don’t care about solids)
https://en.m.wikipedia.org/wiki/Phase_diagram
As water is heated you would reach an equilibrium where the additional volume occupied by the steam increases the pressure in the chamber where no additional water can evaporate. The hotter you get, the more pressure is required and that equilibrium mix of liquid and gas shift up, increasing the pressure.
Eventually you reach the critical point where water is indistinguishable as a liquid or gas. It becomes another state of matter.
A perfect example of the situation the poster described is the common household water heater. If the temp control fails and the relief valve is damaged or in some way purposely disabled, the results are catastrophic. For an eye-opening demonstration, check the Myth Busters water heater explosion on YouTube.
If your container is a solid unbreakable block, than nothing, you could heat it as long as you want.
But in reality the more heat you put in the more water wants to become steam. At 100C steam expands about 1600-1700 times the original water wolume. That is a lot.
If It is not allowed to expand, that is a lot of pressure, the more energy you put in the more pressure you get.
HOWEVER under high pressure you can force water to stay water, way above 100C… Pressurized water reactors is a form of nuclear reactor which uses high pressure water to transfer heat out the reactor at 200 even 300 C That heats normal water.
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pressure affects boiling point of everything. Water can boil at 40-50 C at the top of mount everest or not boil even at 300C under heavy pressure
boiling point is relative to pressure. e.g. at sea level water boils at 212 degrees (f), at 5,000 ft of elevation (less pressure) it boils at 203 degrees. 1000 ft below sea level it takes 214 degrees.
tl/dr it will get hotter but it wont steam/ boil until it’s returned to the room pressure at which point it will boil/ steam.
The science is kind of important here, and its being omitted by many of the top comments.
We state that water boils at 212 degrees F or 100 degrees C but what we don’t generally reference is that those numbers are assuming we are at atmospheric pressure at sea level. We know that water boils at a lower temperature at higher altitudes, you can see this in some recipes or cooking instructions where there is a separate set of instructions for high altitude cooking specifically because when you cook something in boiling water at higher elevation(lower pressure) it doesn’t reach 212 degrees, more like 190 degrees or even lower.
By the same rules, if you increase the pressure you increase the temperature that water boils. This means that as the pressure cooker heats up you cause some water (liquid) to boil and turn into water vapor(steam). Under normal circumstances water turning to steam increase in volume tremendously, around 1800 times as much volume.
So in your pressure cooker you create this moving target of what is the boiling point, as the pressure cooker attempts to increase the amount of water vapor(boiling water), the pressure goes up which means the temperature of the water continues to increase beyond 212 without boiling. Without a way to exhaust water vapor(like the relief valve) or turn off the heat(temperature controls in the electronics of the unit), the temperature and pressure would continue to rise until the device failed.
In reality, you couldn’t realistically reach a temperature where most of the water turned into water vapor, the pressure and temperature would be astronomical to support the vapor not condensing back into liquid water. Your at home pressure cooker still has overwhelmingly water in it until you open the vent on the cooker which lets water vapor out. At that point the water inside will instantly start to boil(its hotter than 212 degrees as discussed and the pressure was just reduced back to atmospheric) and much of the remaining water will quickly boil off.
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