水的黏度表（0〜40 C）
水的物理性质
F3 Viscosity decreases with p ressure
(at temp eratures below 33
Water's p ressure-viscosity behavior [534] can be explained by the in creased p ressure (up to about 150 MPa) caus ing deformatio n, so reduci ng the stre ngth of the hydroge n-bon ded n etwork, which is also p artially res pon sible for the viscosity. This reduct ion in cohesivity more tha n compen sates for the reduced void volume. It is thus a direct con seque nee of the bala nee betwee n hydroge n bonding effects and the van der Waals dis persion forces [558] in water; hydroge n bonding p revaili ng at lower temp eratures and p ressures. At higher p ressures (and den sities), the bala nee betwee n hydroge n bonding effects and the van der Waals dis persi on forces is tipped in favor of the dis persion forces and the rema ining hydroge n bonds are stron ger due
Viscous flow occurs by molecules movi ng through the voids that exist betwee n them. As the p ressure in creases, the volume decreases and the volume of
these voids reduces, so no rmally in creas ing p ressure in creases the viscosity.
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to the closer p roximity of the con tribut ing oxyge n atoms [655]. Viscosity, the n, in creases with p ressure. The dashed line (opp osite) in dicates the viscosity mi ni ma.
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The variati on of viscosity with p ressure and temp erature has bee n used as evide nee
that the viscosity is determ ined more by the exte nt of hydroge n bonding rather tha n
hydroge n bonding stre ngth.
Self-diffusio n is also affected by p ressure where (at low temp eratures) both the tran slatio nal and rotati onal moti on of water ano malously in crease as the p ressure in creases.
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