时差N小时 你知道保鲜膜的原理吗?(上)

What makes kitchen plastic wrap cling so maddeningly to itself, and so conveniently to the sides of bowls and plates?

为何厨房的保鲜膜可以自我吸附，还能巧妙地贴合在碗盘上？

Plastic wrap clings for two reasons: it’s elastic¹ and it’s sticky.

保鲜膜粘附主要有两个原因：弹性和粘性。

That probably seems pretty obvious, but let’s explore the chemistry beneath the elasticity² and stickiness of plastic wrap.

虽然看起来很明显，不过我们还是来探究一下保鲜膜弹性和粘性下的化学原理吧。

Plastic wrap is elastic because of its molecular³ structure.

保鲜膜因其本身的分子结构而具有弹性。

A molecule⁴ of plastic is incredibly long and coiled up like a spring.

塑料的一个分子很长并且可以像弹簧一样蜷曲。

When you stretch out a piece of plastic wrap, you uncoil these long molecules⁵.

当你将一块保鲜膜伸扯开时，同时也拉长了它的分子。

Like a spring, the stretched molecules tend to spring back, perhaps tucking under the rim⁶ of the bowl you just covered!

保鲜膜被拉伸后会像弹簧般收缩，也许就刚好贴合在碗的边缘。

Over time, certain types of plastic wrap lose some of their elasticity, which could explain why that dish you wrapped tightly may loosen up after a day or two.

随着时间推移，有些品种的保鲜膜会逐渐失去弹性。这也就解释了为何紧贴在碗边的保鲜膜会在一两天后松开。

1 elastic   

n.橡皮圈，松紧带；adj.有弹性的；灵活的

参考例句：

• Rubber is an elastic material.橡胶是一种弹性材料。
• These regulations are elastic.这些规定是有弹性的。

2 elasticity   

n.弹性，伸缩力

参考例句：

• The skin eventually loses its elasticity.皮肤最终会失去弹性。
• Every sort of spring has a definite elasticity.每一种弹簧都有一定的弹性。

3 molecular   

adj.分子的；克分子的

参考例句：

• The research will provide direct insight into molecular mechanisms.这项研究将使人能够直接地了解分子的机理。
• For the pressure to become zero, molecular bombardment must cease.当压强趋近于零时，分子的碰撞就停止了。

4 molecule   

n.分子，克分子

参考例句：

• A molecule of water is made up of two atoms of hygrogen and one atom of oxygen.一个水分子是由P妈̬f婘̬ 妈̬成的。
• This gives us the structural formula of the molecule.这种方式给出了分子的结构式。

5 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。

6 rim   

n.(圆物的)边，轮缘；边界

参考例句：

• The water was even with the rim of the basin.盆里的水与盆边平齐了。
• She looked at him over the rim of her glass.她的目光越过玻璃杯的边沿看着他。