[The First Guy]

Please bear with me. I'm sorry if I'm hard to follow.
I know that under 1 standard atmosphere of pressure, water has the following properties:

Freezing/melting point of 0 Celsius
Boiling/condensing point of 100 Celsius
Maximum density of 1.0 g/cm^3 achieved at 4 Celsius

Here's my question: If water were under 0.5 standard atmospheres of pressure or 2 or 3 standard atmospheres of pressure, what numbers would correspond with the above properties and most importantly, would the Maximum density still be 1.0 g/cm^3 and would that still be achieved in the liquid phase?

I do NOT need to know about extreme environments like the high pressures at the bottom of the ocean, or like the vacuum of space. That data is irrelevant to me because I'm only considering pressures at which breathable atmospheres would exist.

Thank you very much and I would love a formula and numbers or a link to a table regarding the all-important MAXIMUM density question: Is the MAXIMUM density that water achieves always 1.0 g/cm^3 under "air-like" conditions that would exist in a range of atmospheric pressures? (not under water)

[Capuchin]

No, maximum density depends on pressure, and will be higher at higher pressures (pretty obviously.. ). The temperature at which maximum density occurs also decreases at higher pressure.

Something like this:


PS. I don't know why you think that bottom of the ocean or outer space is irrelevant to you - the same laws work over the entire ranges of pressures and temperatures.

[The First Guy]

Okay, I'm actually uneducated in physics, so I'm not quite sure of a couple of things. 1 bar is the same as 1 standard atmosphere, right?
Also, there is a reason that I'm not interested in extreme conditions. I understand that the same laws hold true, but for this case I specifically need to know about the range of pressures from about 1/3 or 1/2 standard atmosphere to 3 or 5 standard atmospheres. I appreciate the graph. However, its spread is so vast. Is there some place I could find more confined information with details across the above mentioned range for freezing, boiling and maximum density?

[Perito]

Actually, 1 Bar is 0.98692 atmospheres and 1 atmosphere is 1.01325 Bar. The units are close, but not the same.

[Capuchin]

it's going to be pretty close to 4deg C and 1kg/m^3 for that range of pressures.