【英语时差8,16】为什么冰不滑

 Why Ice Is Not Slippery Try telling someone who has just fallen on a patch of ice that ice is not slippery and they’ll think you’re crazy. But, in fact, ice itself isn’t slippery because it is a solid. One quality of solids is that when two solids are together there is friction¹ between them that will keep them from slipping. So how can your shoe slip on ice? The answer lies in two peculiar² properties of ice. The first is that as water freezes, its molecules³ move farther apart. The molecules of most substances move closer together as they freeze, making them shrink at lower temperatures. But water molecules move farther apart at temperatures below 39 degrees Fahrenheit⁴, making water expand as it freezes. That is why frozen water pipes burst, and a tray of ice cubes will freeze over its top if you fill it too full. The second peculiar property of ice is directly linked to its first peculiarity⁵. When subjected to pressure, ice melts. Remember that the molecules in ice are farther apart than the molecules in water; therefore ice molecules are vulnerable to pressure which pushes them closer together, causing the ice to change into water. So when you step on a patch of ice, you exert pressure on the ice, which causes its molecules to move closer together. That makes them revert⁶ to their more dense⁷ state, which is water. If you slip on a patch of ice, then, you in fact are slipping on a thin layer of water that the pressure from your weight has created. And, unlike solid ice, water, as a liquid , is quite slippery.

 

1 friction   

n.摩擦，摩擦力

参考例句：

• When Joan returned to work,the friction between them increased.琼回来工作后，他们之间的摩擦加剧了。
• Friction acts on moving bodies and brings them to a stop.摩擦力作用于运动着的物体，并使其停止。

2 peculiar   

adj.古怪的，异常的；特殊的，特有的

参考例句：

• He walks in a peculiar fashion.他走路的样子很奇特。
• He looked at me with a very peculiar expression.他用一种很奇怪的表情看着我。

3 molecules   

分子( molecule的名词复数 )

参考例句：

• The structure of molecules can be seen under an electron microscope. 分子的结构可在电子显微镜下观察到。
• Inside the reactor the large molecules are cracked into smaller molecules. 在反应堆里，大分子裂变为小分子。

4 Fahrenheit   

n./adj.华氏温度；华氏温度计(的)

参考例句：

• He was asked for the boiling point of water in Fahrenheit.他被问到水的沸点是华氏多少度。
• The thermometer reads 80 degrees Fahrenheit.寒暑表指出华氏80度。

5 peculiarity   

n.独特性，特色；特殊的东西；怪癖

参考例句：

• Each country has its own peculiarity.每个国家都有自己的独特之处。
• The peculiarity of this shop is its day and nigth service.这家商店的特点是昼夜服务。

6 revert   

v.恢复，复归，回到

参考例句：

• Let us revert to the earlier part of the chapter.让我们回到本章的前面部分。
• Shall we revert to the matter we talked about yesterday?我们接着昨天谈过的问题谈，好吗？

7 dense   

a.密集的，稠密的，浓密的；密度大的

参考例句：

• The general ambushed his troops in the dense woods. 将军把部队埋伏在浓密的树林里。
• The path was completely covered by the dense foliage. 小路被树叶厚厚地盖了一层。