Physics Question #3164

Eduardo, a 14 year old male from Pembroke Pines asks on January 8, 2006,

Is it true that gas particles at higher altitudes are farther away from each other than at lower altitudes, and, if this is true, does it apply to liquid particles too? Do Liquid Particles on say, Mt. Everest have the same pressure as liquid particles at sea level? That is, would an amount of liquid at sea level be "smaller in size", due to greater pressure, than the same amount of liquid on top of Mt. Everest, because the particles of the liquid be pressed closer to each other? If this is true, when does it become noticeable? Finally, does this apply to solids as well?

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The answer

John Jones answered on January 9, 2006

Yes it is true for gasses, but to first approximation, the molecules in a liquid do not become closer together when the pressure increases -- liquids are usually considered to be incompressible. If we measure carefully, though, we do find some compression -- a mile below the ocean's surface, we have a pressure of 175 atmospheres (175 times the normal air pressure at sea level), and the water at that depth is compressed by about 1%. Solids are somewhat less compressible than liquids -- about a third as compressible on average.

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