英語聽力文摘 燒開水的秘密

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You may be surprised to hear that it’s actually easier to boil water on stormy days than it is when the weather is clear and sunny.

Can you guess why?

The reason is that the boiling point of water changes slightly in response to air pressure. High air pressure, found on sunny, clear days, means just what it sounds like: crowded air molecules are pressing down on the water in the pot, just like they press on the stove, the floor and on you. This causes the molecules that make up the water to be squeezed more tightly together, which means that the steam bubbles trying to form at the bottom of the pot have a harder job pressing outward. It’s somewhat like trying to stretch your arms in a crowded room: the more crowded it is, the harder it will be for you to stretch without being bumped back again by someone else.

On stormy days, the air pressure is relatively low; you have probably heard the weather person refer to a “low pressure system” moving in just before it rains. When there is low air pressure the water in your pot is not compressed as much by the air around it. Because it’s easier to displace that water, the bubbles of steam form more easily at the bottom of the pot; and voila — boiling begins.

There is a catch, however. Although the boiling point of water — 212 degrees — is reduced on stormy days, and thus water boils faster, the temperature of that boiling water is also lower. That means it will actually take LONGER to cook things — an effect that more than counters the ten seconds or so you save in waiting for the boil.

譯文：

你或許會覺得驚奇，在暴風雨的天氣比在晴朗的天氣更容易把水燒開。

你猜猜這是為什么呢?

原因就是水的沸點根據(jù)氣壓有細微的變化。高壓一般出現(xiàn)在晴好的天氣，就如聽起來的那樣：擁擠的空氣分子擠壓在鍋里的水上空，就像它們擠壓在爐子，地板以及你的身上一樣。這讓構(gòu)成水的水分子擠壓的更緊，也就意味著在壺底形成的氣泡更難向外冒。這就像在一個狹窄的屋子里，你試圖伸展四肢：它越狹窄，你越難在不被什么東西撞回來的情況下伸展。

在暴風雨的天氣，氣壓相對較低，你或許聽到過天氣預報員報道下雨之前，“低壓系統(tǒng)”正在進入。當?shù)蛪捍嬖诘臅r候，壺里的水不會像周圍的空氣那樣被擠壓，所以水之間的更替的更迅速，蒸汽氣泡在壺底也更容易形成，瞧-已經(jīng)開了。

但是仍有一個不好之處。盡管水的沸點-212度-在暴風雨天氣會降低，水會燒開的比較快，可是開水的溫度也會相對較低。也就是說煮東西的時間就會變長-這就是在等待水開過程中節(jié)約下來的那十秒時間而造成的一種負面效應。