In the Phase Change Update the 7 in-game gases (O2, N2, CO2, N2O, H2O, Volatiles and Pollutant) can now be in three different states; gas, liquid and solid. Gases and solids can exist by themselves, but a liquid will always co-exist with a gas (of any type). Phase changes are not instant, it will take some time for them to reach their endpoint.

<br>'''Freezing temperature''' = where a gas or liquid turns into solid (this will damage pipes!)

<br>(unimportant) '''Boiling temperature''' = the temperature where the "Vapor pressure" is equal to 100kPa (slightly incorrect values)

<br>'''Latent heat''' = the energy per mol released by condensation and consumed by evaporation

<br>(unimportant) '''Min Condensation Pressure''' = below this pressure a gas will not condense into liquid (allows gases to freeze into solids)

<br>'''Max liquid temperature''' = gas can't condense into liquid above this temperature (gas-pipes are safe from liquid damage)

<br>'''Vapor pressure''' = (the pressure given by the graph) a liquid evaporates when below it, a gas condensates when above it

The Stationpedia graphs are divided into 3 different regions. Solid-state to the left, liquid-state in the middle and the gas-state on the right. The term "Vapor pressure" isn't mentioned but is the pressure value that is read from the graph for any given temperature. This value is not completely accurate however, comparing the graph to in-game pressures show that they are slightly off, but it's close enough.

For '''solids''' the "Vapor pressure" is actually zero, even though the graph claims it to be 6.3 kPa (see footnote 1)

For '''liquids''' the "Vapor pressure" is the pressure where a liquid will stop evaporating. This pressure doesn't have to come from the same type of gas, another gas can also provide this pressure. Oxygen is the gas with the lowest value for "Max liquid temperature", which makes it the hardest to liquidize (which would contaminate the liquid it's supposed to pressurize). This makes Oxygen ideal as a pressurant, but Nitrogen and Volatiles are almost as good so these can also be used.

For a '''gas''' with a temperature above the "Max liquid temperature" the "Vapor pressure" means nothing, because it's too hot to undergo any phase-changes. But when the temperature drops below the "Max liquid temperature" the "Vapor pressure" is the lowest pressure required for a gas to start condensating. A gas can also turn into a solid (ice) directly without becoming a liquid first, this will happen if the temperature drops to the freezing point while the pressure of the gas is kept below the "Min Condensation Pressure". This makes pipes with just gas vulnerable to freezing too.

'''Freezing''' is when a gas or liquid becomes solid, this doesn't appear to change the temperature.  

*One-way Valves

Filtration units can separate both gases and liquids, but too much liquid will damage the gas-pipes (unless using an exploit to protect the pipes, see "Pipe damage" above).

Examples:

2) (distillation) A liquid mix of N2O and Pollutant can be separated via a distillation that only evaporates the Pollutant. When comparing the "Vapor pressures" of N2O and Pollutant one can see that for each temperature the Pollutant will always have the higher "Vapor pressure" value. With a Purge Valve or Evaporation Chamber it's possible to keep the pressure above the N2O's "Vapor pressure" and below the Pollutants, which means that only the Pollutant will be able to evaporate. When all the liquid Pollutant has been removed, only Pollutant gas and liquid N2O will remain. An Evaporation Valve can then be used to move just the liquid, but some engineering may be required to prevent pipe damage during this step.

When an AC is used for heating, its waste pipe can get extremely cold. The same goes for using passive Radiators on the Moon or on Mimas (keep the radiators exposed to sunlight to prevent the pipe temperature from getting too low). The best gas choice for cold pipes is Oxygen, since it is the hardest to liquify (-111°C at 6MPa), and all of it should (not properly tested!) turn into a liquid before it freezes into a solid. If the pipe pressure is above 6MPa the excess Oxygen will start to condense when the temperature dips to -111MPa. Attach a "Passive Liquid Drain" is a good way to protect the pipe, any liquid Oxygen will be removed from the pipe before it takes any damage. Instead of using pure Oxygen, crushed Oxite will do just fine, the Nitrogen will condense first and remove itself through the drain.  

 

==Heating/Cooling with phase change loops==

Since condensation increases the temperature and evaporation decreases the temperature, it's possible to build a loop where the gas-side becomes warmer and the liquid-side colder. The Condensation and Evaporation Chambers are good for this (note: a Purge Valve (set to 0 kPa) on the liquid-pipe between them is often necessary to prevent that pipe from breaking), but a phase change loop can also be made from pipes by using a Condensation Valve and a Purge Valve (set to 0kPa). By heating the colder liquid-side, or cooling the warmer gas-side, it's possible to keep the heating/cooling going.

3) on Mars, capture cold night-time atmospheric gas in a pipe with a small/moderate volume, preferably with a fast Powered Vent. Since only Pollutant and CO2 can phase-change into liquids below -8°C, both of these can be removed from the pipe via Passive liquid drains. The O2 and N2 however remains trapped inside. The condensation of CO2 will heat up the pipe (to -8°C), but if the temperature can be kept down the pipe will eventually contain a mix of just O2 and N2.