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Compressibility of Water

Hi,
I've been trying to understand the compressibility of liquids. I can't seem to find anything definitive on the Internet on the subject. All I get is that liquids are practically incompressibile. However, I AM interested in how much they do compress, regardless of how small it is, or how much pressure is needed.

One figure I could was as follows: 0.46 GPa-1

Does this mean that water under 1 GPa (GigaPascal) of pressure will compress by a volumetric factor of 0.46??

If you think it is correct, can you verify this? Do you have a link to some site where this is documented?

Also, I wouldn't think that compression would be a linear function of pressure. Is it? If not, does anyone have a graph that shows water's (or other liquid's) volume as a function of pressure?

Thanks!

Reply 1

sazzles

Quimbly

Hi,
I've been trying to understand the compressibility of liquids. I can't seem to find anything definitive on the Internet on the subject. All I get is that liquids are practically incompressibile. However, I AM interested in how much they do compress, regardless of how small it is, or how much pressure is needed.

One figure I could was as follows: 0.46 GPa-1

Does this mean that water under 1 GPa (GigaPascal) of pressure will compress by a volumetric factor of 0.46??

If you think it is correct, can you verify this? Do you have a link to some site where this is docu*mented?

Also, I wouldn't think that compression would be a linear function of pressure. Is it? If not, does anyone have a graph that shows water's (or other liquid's) volume as a function of pressure?

Thanks!

Really interesting question! I'd never thought about it. This link takes you to some data on volumes, temperatures and pressure of water. You might be able to fiddle it to make it what you need.
http://van.hep.uiuc.edu/van/qa/section/Underwater_and_in_the_Air/Pressure/20030603113030.htm
Hope that helps.

Reply 2

Quimbly

OP

Thank you, this is a start. However, I'm looking at larger pressures than this. I'm trying to figure out what the environment would be like at the bottom of the ocean. According to this link, http://www.nodc.noaa.gov/General/NODC-oceanfaq.html
the deepest pit in the ocean is around 11,000 meters down. According to one estimate I discovered, the pressure at 10,000 meters would be around 10,000 atm (roughly 1 GPa). I'm not sure if those estimates are accurate, but these are the numbers I'm looking for verify also.

Anyone else with info on the subject?

Reply 3

sazzles

There'e another question in that section about pressure in the ocean;
http://van.hep.uiuc.edu/van/qa/section/Underwater_and_in_the_Air/Pressure/20020205114842.htm
Is that more what you are looking for?

Reply 4

sazzles

I can also give you the derivation of the formula for the pressure in a column of fluid (liquid or gas) height h, density ρ and cross sectional area A;
Volume of fluid in column=hA
mass of fluid=hAρ
Weight of fluid=hAρg
Pressure=weight/area=hAρg/A=hρg
This will only be useful if you can find the density of the water, though.

Reply 5

Quimbly

OP

Cool, yes, this is another good link. Thanks again!

So, according to this formula, the pressure at a depth of 10,000 meter (in fresh water, anyway), at the same atmospheric pressure above the water, would be 98,101,000 Pascals, which (If I'm not mistaken) is 0.98101 GPa.

Excellent. So, this verifies my pressure assumptions. Now all I need to do is find some number to verify the compressibility of water under pressures around 1 GPa.

Also, would anyone know how cold it would be at the bottom of the ocean (10,000m) ??

Reply 6

Quimbly

OP

Ok, I found some info on ocean water density:
http://www.windows.ucar.edu/tour/link=/earth/Water/density.html&edu=high

It looks like it stays at around 1028 g / cm^3 for depths below 1000m.

What next?

Reply 7

FANNY HOLE

You can compress liquid why do you think pressure increases with depth of Oqean for example? Course you can.

Reply 8

Quimbly

OP

Well, the question was never whether or not you can compress liquids. The question was: by HOW MUCH does water compress under great pressures, (e.g. water at the bottom of the ocean)?

Reply 9

FANNY HOLE

Quimbly

Well, the question was never whether or not you can compress liquids. The question was: by HOW MUCH does water compress under great pressures, (e.g. water at the bottom of the ocean)?

Well I don't know that, but the question also mentioned that compressing liquid is practially impossible. Well in so many words:

All I get is that liquids are practically incompressibile.

Reply 10

Quimbly

OP

FANNY HOLE

Well I don't know that, but the question also mentioned that compressing liquid is practially impossible. Well in so many words:

Well, I appologize if it was unclear. However, the point was that I am looking for the compressibility factor of water at high pressures, and all I could find on the Internet was that "liquids are practically incompressible". I wasn't saying that liquids weren't compressible. How could I be?! I'm looking for compressibility factors!!!

Reply 11

FANNY HOLE

Quimbly

Well, I appologize if it was unclear. However, the point was that I am looking for the compressibility factor of water at high pressures, and all I could find on the Internet was that "liquids are practically incompressible". I wasn't saying that liquids weren't compressible. How could I be?! I'm looking for compressibility factors!!!

Fair dinkum, well im not a physicist so dont know sorry

Reply 12

Quimbly

OP

FANNY HOLE

Fair dinkum, well im not a physicist so dont know sorry

Where on earth did you get such digusting pictures?

Reply 13

username9816

14

if they were of actual people then i would be afraid right now!

Reply 14

sazzles

Quimbly

Also, would anyone know how cold it would be at the bottom of the ocean (10,000m) ??

Again, I know nothing, but this link seems to suggest ocean floor temperatures are very variable.
http://www.gsfc.nasa.gov/gsfc/educ/science/2001/11-09-00.htm

Reply 15

sazzles

This site says the current temp varies between 1.9-22.8oC, but I'm rather dubious of the accuracy.
http://www.arm.gov/docs/education/lessons/pacifictemp.html

Reply 16

Quimbly

OP

Let's assume that the temperature is fairly standard, and that we're not near any fissures to the mantle.

http://www.windows.ucar.edu/tour/link=/earth/Water/temp.html&edu=high

This site would indicate that the temperature would be somewhere between 0 and 3 degrees C at a depth of 10,000m. Let's go with that.