時(shí)差N小時(shí):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(gè)剛在冰上滑倒的人冰其實(shí)不滑，那人肯定會(huì)覺(jué)得你瘋了。不過(guò)事實(shí)的確如此，冰本身并不滑，因?yàn)樗枪腆w。固體的一個(gè)特點(diǎn)就是當(dāng)兩個(gè)固體接觸時(shí)會(huì)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(huì)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(jié)冰時(shí)，水分子分離得更遠(yuǎn)。但多數(shù)物質(zhì)在結(jié)冰時(shí)，分子會(huì)緊密聚集在一起，溫度一降低物質(zhì)就會(huì)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(dāng)溫度低于39攝氏度時(shí)，水分子會(huì)分散開(kāi)來(lái)，因此結(jié)冰后冰的體積大于水的體積。這就是為什么水管會(huì)凍裂，用盤(pán)子盛滿水，結(jié)冰后冰面會(huì)超過(guò)容器的平面。冰的第二種特性與第一種特性是直接相關(guān)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(huì)融化。記住冰的分子比在水的狀態(tài)時(shí)更分散，受壓后導(dǎo)致分子聚集，此時(shí)冰會(huì)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(dāng)你踏在一塊冰上時(shí)，會(huì)對(duì)它產(chǎn)生壓力，這個(gè)壓力導(dǎo)致分子相互間靠得更近，使之恢復(fù)到更加緊密的形態(tài)——水。如果你在冰面上打滑了，實(shí)際上是你在一層薄薄的水面上打滑了，而這些水正是因?yàn)槟泱w重帶來(lái)的壓力導(dǎo)致的。跟固態(tài)的冰不一樣，液態(tài)的水是相當(dāng)滑的。