– Why is water ‘virtually’ incompressible?
In: 30
“Virtually” means that it’s a little compressible, but so little that you can do all your math assuming it’s not compressible at all, and the end result won’t be different enough to matter
“Virtually” means that it’s a little compressible, but so little that you can do all your math assuming it’s not compressible at all, and the end result won’t be different enough to matter
Because nothing is TRULY incompressible. Any liquid or solid will be squished a bit under pressure. IIRC water density increases by a few tens of a percent under tens or hundreds of atmospheres. You have to be doing something hyper specific for that difference to matter.
In comparison, you can decrease the volume of air a few hundred times, until the gasses eventually turn to liquid themselves under pressure. The tiny CO2 canisters used in airsoft hold 60 liters of gas, for example.
Water is compressible, but not too much.
It’s just that gases are very very very compressible.
If you have ever tried to compress a closed, empty syringe before, you are able to compress it somewhat with a little difficulty.
To get an idea for that, i want you to guess how many air molecules there are in a small cube(take 1cm sided cube for example).
A million? Seems low, a billion maybe? Even a trillion?
Nope, its around 10^16 atoms. That’s like a million trillion. Seems very large.(Incorrect)
Now guess how many atoms in one cm³ of water? Maybe like 10 or 100 times more?
Nope, its around 10^22 atoms. Basically a million times more atoms. Not too difficult to see why that might be hard to compress.
Of course, there are several other factors at play, like the energy of gas particles, the intermolecular attraction of water, attraction of the gas molecules, relation between temperature and pressure, and many more. Although i do think the significantly more amount of water molecules is the biggest reason for the less compressibility of water (or of any liquids, compared to gas).
Tldr: Water(or any liquid) has a lot more atoms than any gas. So its much harder to compress.
Edit: Whoops, use a few wrong numbers in the formulas
The number of atoms in one cm³ of air is around 10^19. That water/air molecules factor to around 1000. Should still. Still that’s a lot more atoms.
Water is compressible, but not too much.
It’s just that gases are very very very compressible.
If you have ever tried to compress a closed, empty syringe before, you are able to compress it somewhat with a little difficulty.
To get an idea for that, i want you to guess how many air molecules there are in a small cube(take 1cm sided cube for example).
A million? Seems low, a billion maybe? Even a trillion?
Nope, its around 10^16 atoms. That’s like a million trillion. Seems very large.(Incorrect)
Now guess how many atoms in one cm³ of water? Maybe like 10 or 100 times more?
Nope, its around 10^22 atoms. Basically a million times more atoms. Not too difficult to see why that might be hard to compress.
Of course, there are several other factors at play, like the energy of gas particles, the intermolecular attraction of water, attraction of the gas molecules, relation between temperature and pressure, and many more. Although i do think the significantly more amount of water molecules is the biggest reason for the less compressibility of water (or of any liquids, compared to gas).
Tldr: Water(or any liquid) has a lot more atoms than any gas. So its much harder to compress.
Edit: Whoops, use a few wrong numbers in the formulas
The number of atoms in one cm³ of air is around 10^19. That water/air molecules factor to around 1000. Should still. Still that’s a lot more atoms.
Because nothing is TRULY incompressible. Any liquid or solid will be squished a bit under pressure. IIRC water density increases by a few tens of a percent under tens or hundreds of atmospheres. You have to be doing something hyper specific for that difference to matter.
In comparison, you can decrease the volume of air a few hundred times, until the gasses eventually turn to liquid themselves under pressure. The tiny CO2 canisters used in airsoft hold 60 liters of gas, for example.
Imagine water molecules as really tiny, stubborn balls. When you try to squeeze them together, they push back really, really hard, making it almost impossible to make water take up less space. That’s why we say water is “virtually” incompressible because it’s really tough to squash it down.
Imagine water molecules as really tiny, stubborn balls. When you try to squeeze them together, they push back really, really hard, making it almost impossible to make water take up less space. That’s why we say water is “virtually” incompressible because it’s really tough to squash it down.
How compressed is the water at the bottom of the ocean?
How compressed is the water at the bottom of the ocean?
Latest Answers