2.21 蒸发
Section outline
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The clothes on this clothesline are soaking wet, but before too long they will be completely dry. How does this happen? Where does the water go? And what factors might help the clothes on the line dry more quickly?
::衣裙上的衣服湿透了,但不久它们就会完全干涸。 怎么会这样? 水流向哪里? 哪些因素能帮助线上的衣服干得更快?From Liquid to Gas Without Boiling
::从液体到气体无沸水Evaporation explains why clothes dry on a clothesline. Evaporation is the process in which a changes to a without becoming hot enough to boil. It occurs when individual liquid particles at the exposed surface of the liquid absorb just enough to overcome the force of attraction with other liquid particles. If the surface particles are moving in the right direction, they will pull away from the liquid and move into the air. This is illustrated in the Figure .
::蒸发可以解释为什么衣服在衣绳上干燥。 蒸发是一个过程, 在一个过程中, 一个变化不会变得热到足以煮沸。 当液体的暴露表面的单个液体粒子吸收到足以克服与其他液体粒子的吸引力。 如果表面粒子向正确的方向移动, 它们会从液体中拉开并移动到空气中。 这一点在图中说明 。Factors That Affect the Rate of Evaporation
::影响蒸发率的因素Many factors influence how quickly a liquid evaporates. They include:
::许多因素影响液体蒸发的速度。-
of the liquid. A cup of hot water will evaporate more quickly than a cup of cold water.
::一杯热水会比一杯冷水蒸发得更快 -
exposed surface area of the liquid. The same amount of water will evaporate more quickly in a wide shallow bowl than in a tall narrow glass.
::同样的水量会在宽浅的浅碗中蒸发,比在一个高深的狭窄玻璃杯中蒸发的快。 -
presence or absence of other substances in the liquid. Pure water will evaporate more quickly than
salt
water.
::纯水将比盐水蒸发得更快。 -
air movement. Clothes on a clothesline will dry more quickly on a windy day than on a still day.
::衣服上的衣服会在风天干得比静静的一天干得更快 -
of the evaporating substance in the air. Clothes will dry more quickly when air contains little water vapor.
::当空气中含有少量水蒸气时,衣服会干得更快。
Evaporative Cooling
::蒸汽冷却Did you ever notice that moving air cools you down when you’re hot and sweaty? For example, if you sit in front of a fan, you feel cooler. That’s because moving air helps to evaporate the sweat on your skin. But why does the evaporation of sweat cool you down? When a liquid such as sweat evaporates, energetic particles on the surface of the liquid escape into the air. After these particles leave, the remaining liquid has less energy, so it is cooler. This is called evaporative cooling.
::你是否注意到,当热热汗时,移动空气会使你降温?例如,如果你坐在风扇前面,你会感到更凉爽。这是因为移动空气有助于将汗水蒸发在皮肤上。但是,为什么汗水蒸发会使你降温呢?当流汗等液体蒸发时,流到空气中的充满活力的粒子会释放出来。这些粒子离开后,剩下的液体能量会减少,因此更冷。这被称为蒸发冷却。Q: On a hot day, high humidity makes you feel even hotter. Can you explain why?
::问:在炎热的一天,高湿度使你感到更热。你能解释为什么吗?A: Humidity is a measure of the amount of water vapor in the air. When humidity is high, sweat evaporates more slowly because there is already a lot of water vapor in the air. The slower evaporation rate reduces the potential for evaporative cooling.
::A:湿度是测量空气中水蒸发量的尺度。当湿度高时,汗水蒸发速度会更慢,因为空气中已经有大量水蒸发。蒸发速度的减缓降低了蒸发冷却的可能性。Summary
::摘要-
Evaporation is the process in which a liquid changes to a gas without becoming hot enough to boil. It occurs only at the exposed surface of a liquid.
::蒸发过程是液态改变气体而没有热到足以沸腾的过程,它只在液体的暴露表面发生。 -
Many factors affect how quickly a liquid evaporates, including the temperature of the liquid and air movement.
::许多因素影响液体蒸发的速度,包括液体和空气运动的温度。 -
When particles evaporate from the surface of a liquid, the remaining liquid is cooler because it has less energy. This is called evaporative cooling.
::当粒子从液体表面蒸发时,剩余的液体会更冷却,因为它的能量较少。这被称为蒸发冷却。
Review
::回顾-
Define evaporation, and describe how it occurs.
::定义蒸发,并描述它是如何发生的。 -
List four factors that influence the rate of evaporation.
::列出影响蒸发速度的四个因素。 -
What is evaporative cooling? Why does it happen?
::什么是蒸发式冷却?为什么会发生? -
Dorrance mopped the floor and now it is wet. She wants the floor to dry more quickly, so she plugs in an electric fan, aims it at the floor, and turns it on. Do you think this will help the floor dry faster? Why or why not?
::Dorrance 擦地板,现在地板湿透了。 她希望地板干得更快, 所以她用电扇插上电扇, 瞄准地板, 打开它。 你觉得这样能帮助地板干得更快吗? 为什么不行?
Resources
::资源 -
of the liquid. A cup of hot water will evaporate more quickly than a cup of cold water.
