I'm thoroughly confused by the relationship between the Melting Point of Water and pressure. Some sources suggest that since water expands upon freezing, applying pressure makes it "harder" for the water to expand in volume, thus requiring a greater amount of energy, and thus a greater melting point. Other sources suggest that water does indeed have a lower melting point under greater pressure. Clearly I'm misunderstanding something. What am I missing?
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$\begingroup$ Your first link, the video, does not say what you report. (It says that the melting temperature of water "doesn't change very much" with increasing pressure. It's ignoring the actual decrease as negligible.) $\endgroup$– ChemomechanicsCommented Jan 21, 2022 at 19:55
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Just bear in mind that water has the highest density at 4 Celsius.
Increasing the pressure will increase their melting point, in accordance with Le Chatelier's principle.
Since they expand upon melting, an increase in pressure tends to prevent it from melting, therefore raising their melting point.
With water, it contracts upon melting, so an increase in pressure is encouraging melting, and so, its melting point decreases.
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$\begingroup$ @Qmechanic I posted identical answers because they were identical questions. Is it possible for you to undelete my answer to the other question? physics.stackexchange.com/a/691584/2451 $\endgroup$ Commented Jun 30, 2022 at 18:11
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$\begingroup$ Hi QuantumYitian: If you are willing to give up this answer in exchange, it is likely that this could be arranged with the mod @rob that deleted it. Note however that the votes are different. $\endgroup$– Qmechanic ♦Commented Jun 30, 2022 at 18:30