時差N小時:為什么冰不滑

Try telling someone who has just fallen on a patch ofice that ice is not slippery and they'll think you'recrazy. But, in fact, ice itself isn't slippery because itis a solid. One quality of solids is that when twosolids are together there is friction between themthat will keep them from slipping.

告訴某個剛在冰上滑倒的人冰其實不滑，那人肯定會覺得你瘋了。不過事實的確如此，冰本身并不滑，因為它是固體。固體的一個特點就是當兩個固體接觸時會產(chǎn)生摩擦防止打滑。

So how can your shoe slip on ice? The answer lies in two peculiar properties of ice. The first isthat as water freezes, its molecules move farther apart. The molecules of most substancesmove closer together as they freeze, making them shrink at lower temperatures.

因此，為什么你的鞋子會在冰上打滑?原因在于冰具有兩種特性。第一種特性就是水結冰時，水分子分離得更遠。但多數(shù)物質在結冰時，分子會緊密聚集在一起，溫度一降低物質就會收縮。

But water molecules move farther apart at temperatures below 39 degrees Fahrenheit, makingwater expand as it freezes. That is why frozen water pipes burst, and a tray of ice cubes willfreeze over its top if you fill it too full. The second peculiar property of ice is directly linked toits first peculiarity.

但當溫度低于39攝氏度時，水分子會分散開來，因此結冰后冰的體積大于水的體積。這就是為什么水管會凍裂，用盤子盛滿水，結冰后冰面會超過容器的平面。冰的第二種特性與第一種特性是直接相關的。

When subjected to pressure, ice melts. Remember that the molecules in ice are farther apartthan the molecules in water; therefore ice molecules are vulnerable to pressure whichpushes them closer together, causing the ice to change into water.

冰在壓力作用下會融化。記住冰的分子比在水的狀態(tài)時更分散，受壓后導致分子聚集，此時冰會變成水。

So when you step on a patch of ice, you exert pressure on the ice, which causes itsmolecules to move closer together. That makes them revert to their more dense state, whichis water. If you slip on a patch of ice, then, you in fact are slipping on a thin layer of waterthat the pressure from your weight has created. And, unlike solid ice, water, as a liquid , isquite slippery.

所以，當你踏在一塊冰上時，會對它產(chǎn)生壓力，這個壓力導致分子相互間靠得更近，使之恢復到更加緊密的形態(tài)——水。如果你在冰面上打滑了，實際上是你在一層薄薄的水面上打滑了，而這些水正是因為你體重帶來的壓力導致的。跟固態(tài)的冰不一樣，液態(tài)的水是相當滑的。