【英语时差8,16】谈谈减肥

 Why does blowing on hot soup help to cool it off? It’s because of evaporation¹. Evaporation cools down a liquid because the most energetic molecules³ leap off the surface and leave the slower-moving molecules behind. Slower-moving means lower temperature. The more a liquid evaporates, the more it loses heat. The hot soup forms a little cloud of vapor² above it that prevents more evaporation from taking place. The fast-moving molecules can’t escape the soup any more, because this little fog of water vapor has saturated⁴ the air. It just can’t take any more vapor, but blow that cloud away and the fastest molecules can escape the soup! The more you help the fastest molecules to escape the soup, the more you help the soup to cool off.

1 evaporation   

n.蒸发，消失

参考例句：

• Be careful not to lose too much liquid by evaporation.小心不要因蒸发失去太多水分。
• Our bodies can sweat,thereby losing heat by evaporation.我们的身体能出汗，由此可以蒸发散热。

2 vapor   

n.蒸汽，雾气

参考例句：

• The cold wind condenses vapor into rain.冷风使水蒸气凝结成雨。
• This new machine sometimes transpires a lot of hot vapor.这部机器有时排出大量的热气。

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 saturated   

a.饱和的，充满的

参考例句：

• The continuous rain had saturated the soil. 连绵不断的雨把土地淋了个透。
• a saturated solution of sodium chloride 氯化钠饱和溶液