英國學生科學讀本 Lesson 70 蒸發(fā)作用(1)

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第70課 蒸發(fā)作用

Let us fill a small kettle with water, and place it on the fire. The water will soon begin to boil. After an hour or so we shall find the kettle quite empty, although no one has touched it since it was placed on the fire.

我們找上一個水壺, 灌滿水, 放在火上。很快, 水就會沸騰起來。經(jīng)過一個小時左右, 我們會發(fā)現(xiàn)水壺已經(jīng)空空如也。但是水壺放到火上之后, 根本沒有人動過。

What has become of the water which we poured into the kettle? It has all been changed into a vapour or gas, called steam, which has passed out of the mouth of the kettle and mixed with the air in the room. Because the liquid water has changed into vapour, we say that it has evaporated.

那么, 我們倒進去的水去了哪里呢? 它們變成了水蒸氣, 經(jīng)過壺嘴跑了出去, 并且與房間里的空氣混合在了一起。我們將這種液態(tài)水變成水蒸氣的過程稱為蒸發(fā)作用。

But we need not put water on the fire to make it evaporate. Let us place a saucer full of water on the mantel-piece, or out in the garden if the weather is fine. In a few hours the water will have changed into water-vapour and mingled with the air, and the saucer will be quite dry. We cannot see the water-vapour in the air, for it has no colour, and is quite transparent. The water in the saucer will evaporate much more slowly than that in the kettle, and we cannot see rising from it any of the white wreaths which we usually call steam.

不過呢, 我們并不需要將水放在火上才能實現(xiàn)蒸發(fā)作用?，F(xiàn)在, 我們將一碟水放在壁爐架上, 如果天氣好, 也可以放在花園中。幾個小時之后, 這一碟水就將變成水蒸氣與空氣混合在一起, 而碟子也就變得完全干燥。我們無法看到空氣中的水蒸氣, 因為它沒有顏色而且完全透明。與水壺相比, 碟子中的水蒸發(fā)速度要慢上很多, 而且我們也無法觀察到通常被稱為水蒸氣的那種白色氣圈。

The hotter the place is in which we put the water, the more quickly will it evaporate. On a hot, dry, and windy day, water placed in the open air evaporates very quickly indeed. Your mother will tell you that such days are the best for drying clothes that have been washed. The water soon evaporates, and leaves the clothes quite dry.

水放的地方越熱, 蒸發(fā)速度就越快。如果遇到炎熱、干燥且有風的天氣, 放置在戶外的水很快就會蒸發(fā)。媽媽一定會告訴你, 這樣的天氣最適合晾曬剛剛清洗過的衣服。水分將會很快蒸發(fā), 而衣服就變得非常干爽。

Some liquids evaporate more quickly than others. Alcohol, or spirit of wine, evaporates more quickly than water. Dip one finger into alcohol, and another finger into water, and then wave both in the air.

不同液體的蒸發(fā)速度存在一定差異：酒精比水的蒸發(fā)速度要快上不少。你可以用一根手指沾一些酒精, 另一根手指沾上水, 然后分別在空氣中揮動。

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