– Why is water ‘virtually’ incompressible?
In: 30
Most liquids are very hard to compress. Same as solids. Only gases and plasma is easily compressible due to the amount of freedom the atoms have
Most liquids are very hard to compress. Same as solids. Only gases and plasma is easily compressible due to the amount of freedom the atoms have
Not a chemist, so someone will be able to poke holes in this explanation. Please do.
Water is made up of three atoms: one oxygen and two hydrogen atoms. They bond because the oxygen atom is able to “steal” the electrons away from the hydrogen atoms. These are called covalent bonds.
What this does is it creates positive and negative sides of the molecule. The hydrogen sides are positive (from their single proton) and the oxygen from the increase in the electrons (2 extra electrons.)
Normally, a molecule like that would have the two hydrogen atoms be as far apart from each other as possible. They’re both positive, they both repel the other, and they don’t WANT to be near each other.
But, in water, the hydrogen atoms are at an angle (104.5 degrees) instead of being opposite to each other (180 degrees). (No, I don’t know why. Water is weird.) This means the entire atom has a strong electromagnetic difference. One side of the atom is positive (between the two positives) and the other side is negative.
Because those differences are across ALL the water molecules, the atoms do not like being near each other. Like, REALLY do not like being near each other. That’s why, even when you make water into a solid (freezing), the water molecules want to stay farther apart than when they’re free to move (liquid). That’s why water is one of the only substances that exists where the solid is less dense than the liquid (ice floats in liquid water).
Yes, you CAN compress water. But, in functional terms f human experience and engineering, that compressibility is negligible.
At 6000 psi, water only compresses 1.8%. There’s not a lot of places where we compress things to 6000 psi, not even in most hydraulic systems. And most other things compress more than that. We don’t use it for hydraulic systems because water under pressure becomes really reactive. It corrodes things.
Not a chemist, so someone will be able to poke holes in this explanation. Please do.
Water is made up of three atoms: one oxygen and two hydrogen atoms. They bond because the oxygen atom is able to “steal” the electrons away from the hydrogen atoms. These are called covalent bonds.
What this does is it creates positive and negative sides of the molecule. The hydrogen sides are positive (from their single proton) and the oxygen from the increase in the electrons (2 extra electrons.)
Normally, a molecule like that would have the two hydrogen atoms be as far apart from each other as possible. They’re both positive, they both repel the other, and they don’t WANT to be near each other.
But, in water, the hydrogen atoms are at an angle (104.5 degrees) instead of being opposite to each other (180 degrees). (No, I don’t know why. Water is weird.) This means the entire atom has a strong electromagnetic difference. One side of the atom is positive (between the two positives) and the other side is negative.
Because those differences are across ALL the water molecules, the atoms do not like being near each other. Like, REALLY do not like being near each other. That’s why, even when you make water into a solid (freezing), the water molecules want to stay farther apart than when they’re free to move (liquid). That’s why water is one of the only substances that exists where the solid is less dense than the liquid (ice floats in liquid water).
Yes, you CAN compress water. But, in functional terms f human experience and engineering, that compressibility is negligible.
At 6000 psi, water only compresses 1.8%. There’s not a lot of places where we compress things to 6000 psi, not even in most hydraulic systems. And most other things compress more than that. We don’t use it for hydraulic systems because water under pressure becomes really reactive. It corrodes things.
It depends on the context. At Earth’s surface at about one atmosphere of pressure, you can put air in a canister and push on it pretty easily to squeeze it and increase its pressure. For a liquid, you need very high pressures (and thus strong/stiff containers) and pretty sensitive measuring devices to detect it.
https://www.usgs.gov/special-topics/water-science-school/science/water-compressibility says that 150x atmospheric pressure water will compress by 1%. That same pressure would compress a gas to less than 1% of its volume at the surface.
“Virtually” comes from being able to say that the effect is small enough that it can be ignored to make the calculations easier. How much gravity is there between your body and your neighbor? It can be calculated, but it is so tiny relative to the gravity between your body and Earth, so it can be ignored.
It depends on the context. At Earth’s surface at about one atmosphere of pressure, you can put air in a canister and push on it pretty easily to squeeze it and increase its pressure. For a liquid, you need very high pressures (and thus strong/stiff containers) and pretty sensitive measuring devices to detect it.
https://www.usgs.gov/special-topics/water-science-school/science/water-compressibility says that 150x atmospheric pressure water will compress by 1%. That same pressure would compress a gas to less than 1% of its volume at the surface.
“Virtually” comes from being able to say that the effect is small enough that it can be ignored to make the calculations easier. How much gravity is there between your body and your neighbor? It can be calculated, but it is so tiny relative to the gravity between your body and Earth, so it can be ignored.
Solids and liquids are called “condensed states”
This simply means that all the atoms and molecules are really close to each other so there’s no space to force out to get them closer (i.e. compress them).
In a gas, molecules are really far apart so they are compressible.
Solids and liquids are called “condensed states”
This simply means that all the atoms and molecules are really close to each other so there’s no space to force out to get them closer (i.e. compress them).
In a gas, molecules are really far apart so they are compressible.
Note, virtually here is not a scientific word.
Its like when someone says something is “virtually impossible!” Its not actually impossible, it just might be very very difficult.
Latest Answers