[ELI5] Can one physically compress water, like with a cyclinder of water with a hydraulic press on the top, completely water tight, pressing down on it, and what would happen to the water?
In: 1967
I mean, you can try.
In engineering contexts, water is generally referred to as “incompressible,” which isn’t to say that it literally can’t be compressed, but that it’s exceptionally difficult to do so.
>and what would happen to the water?
The water would be fine and would escape through the weakest point in the press. The hydraulic press would probably be damaged or destroyed.
Yes. Water is not completely incompressible. Increased pressures will vary its density slightly, and at extreme pressures (on the order of >=1 GPa), water will solidify, even at room temperature.
Ice / water / water vapour phase transitions are described by a phase diagram. Water ice can take several different forms depending on the combination of temperature and pressure.
The most likely thing to happen is for the hydraulic press stalling out and not have enough power to push down any further or the metal in the cylinder or the press would fail and start bending.
But you are right that water, just like everything else, does compress under pressure. It is not much though and it required a lot of pressure until it gets noticeable. If you get it to extremely high pressures it will form ice which is less dense then water. And again at even higher pressures the ice changes into other crystal forms of ice. But your small hydraulic press found in most large industrial shops is not able to produce such high pressures.
Yes. Water is not completely incompressible. Increased pressures will vary its density slightly, and at extreme pressures (on the order of >=1 GPa), water will solidify, even at room temperature.
Ice / water / water vapour phase transitions are described by a phase diagram. Water ice can take several different forms depending on the combination of temperature and pressure.
The most likely thing to happen is for the hydraulic press stalling out and not have enough power to push down any further or the metal in the cylinder or the press would fail and start bending.
But you are right that water, just like everything else, does compress under pressure. It is not much though and it required a lot of pressure until it gets noticeable. If you get it to extremely high pressures it will form ice which is less dense then water. And again at even higher pressures the ice changes into other crystal forms of ice. But your small hydraulic press found in most large industrial shops is not able to produce such high pressures.
I mean, you can try.
In engineering contexts, water is generally referred to as “incompressible,” which isn’t to say that it literally can’t be compressed, but that it’s exceptionally difficult to do so.
>and what would happen to the water?
The water would be fine and would escape through the weakest point in the press. The hydraulic press would probably be damaged or destroyed.
The most likely thing to happen is for the hydraulic press stalling out and not have enough power to push down any further or the metal in the cylinder or the press would fail and start bending.
But you are right that water, just like everything else, does compress under pressure. It is not much though and it required a lot of pressure until it gets noticeable. If you get it to extremely high pressures it will form ice which is less dense then water. And again at even higher pressures the ice changes into other crystal forms of ice. But your small hydraulic press found in most large industrial shops is not able to produce such high pressures.
I mean, you can try.
In engineering contexts, water is generally referred to as “incompressible,” which isn’t to say that it literally can’t be compressed, but that it’s exceptionally difficult to do so.
>and what would happen to the water?
The water would be fine and would escape through the weakest point in the press. The hydraulic press would probably be damaged or destroyed.
As others have said, water is considered incompressible for all practical purposes. That’s why hydraulics are so powerful. It’s why you can lift a car on a column of oil. If the liquids compressed, it wouldn’t work.
When you learn about air as a fluid, and related principles like Bernoulli, one of the first things they teach you is that gaseous fluids can generally be compressed, but liquid fluids like water cannot.
Others have explained here that this is a general principle for practical purposes, not an inviolable law. Apparently you can compress water, but not with the pressures associated with normal equipment used in hydraulics.
This is a great question. Good job, OP
Liquids are generally considered incompressible, so in your scenario you would not be able to compress the water, you would simply reach the point at which the cylinder holding the water would burst. That said different liquids do compress slightly, but not a noticeable amount. This is why hydraulic systems are so efficient and effective, the oil used cannot be compressed.
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