58 The Water Cycle-Mid

The Water Cycle Written by Robert N. Knight

《水循环》罗伯特·N。 骑士

Introduction Water covers three-fourths of Earth's surface. Other planets have only traces of water or no water at all This is why Earth is called the "water planet." As the number of people on Earth increases, more water is used. More people also mean more pollution. Earth's fresh water becomes more and more precious. In this book, you will learn about how Earth's water moves and changes. You will also learn how it is used and why it must be protected and conserved.

水覆盖了地球表面的四分之三。 其他行星上只有水的痕迹，或者根本没有水，这就是为什么地球被称为“水行星”。 随着地球上人口的增加，水的使用量也在增加。 更多的人也意味着更多的污染。 地球上的淡水变得越来越珍贵。 在这本书中，你将了解到地球上的水是如何移动和变化的。 您还将了解如何使用它，以及为什么必须保护和保存它。

The majority of Earth's water is found in the oceans that cover most of Earth's surface. Ocean water has many minerals. These minerals make ocean water taste salty. For this reason, ocean water is called salt water. The water that is not found in the oceans is called fresh water. Only 3 percent of Earth's water is fresh water. Fresh water is found in lakes, rivers, and streams. It is also found under the ground. Most of Earth's fresh water is ice. It is found around the North and South Poles in ice sheets and icebergs. It is also found in mountain glaciers.

地球上大部分的水是在覆盖地球表面大部分的海洋中发现的。 海水含有许多矿物质。 这些矿物质使海水有咸味。 因此，海水被称为盐水。 在海洋中找不到的水叫做淡水。 地球上只有3%的水是淡水。 淡水存在于湖泊、河流和小溪中。 它也被发现在地下。 地球上大部分的淡水都是冰。 它在南极和北极的冰原和冰山中被发现。 它也存在于高山冰川中。

The Movement of Water Everything on Earth is made of matter. The three states of matter are solid, liquid, and gas. Most water on Earth is liquid. Some of it is solid ice and some is a gas we can't see. That gas is called water vapor. Earth's water moves in a cycle called the water cycle. As it moves from place to place, it changes from liquid to gas and gas to liquid. It also changes from liquid to solid and solid to liquid.

地球上的一切都是由物质构成的。 物质的三种状态是固体、液体和气体。 地球上大部分水都是液体。 有些是固态冰，有些是我们看不见的气体。 这种气体叫做水蒸气。 地球上的水在一个叫做水循环的循环中运动。 当它从一处移动到另一处时，它从液体变成气体，再从气体变成液体。 它也会从液体变成固体，从固体变成液体。

Water needs energy to change from liquid to gas or from solid to liquid. The energy it needs comes from the Sun. When water changes from liquid to water vapor, the process is called evaporation. This is the first step in the water cycle. Sunlight hits water on Earth's surface. Tiny particles that make up water, called water molecules, absorb some of the light energy and begin to move. As they get more energy from the Sun, they move even faster. When they get enough energy, they escape the liquid water and enter the air as water vapor.

水从液体变成气体或从固体变成液体需要能量。 它所需要的能量来自太阳。 当水从液体变成水蒸气时，这个过程叫做蒸发。 这是水循环的第一步。 阳光照射到地球表面的水上。 构成水的微小粒子，称为水分子，吸收了一些光能并开始移动。 当它们从太阳获得更多的能量时，它们移动得更快。 当它们获得足够的能量时，就会脱离液态水，以水蒸气的形式进入空气。

When warm air near Earth's surface begins to rise, it cools. As the air cools, the water molecules in the air begin to slow down and lose energy. They collect on dust particles floating in the air. These molecules join other molecules and form tiny water droplets. As they lose energy, they change back to a liquid. This process is called condensation. That's the next step in the water cycle. As more and more water droplets gather on dust particles, clouds begin to form. As more droplets form, the clouds get thicker and thicker. The clouds can get so thick, that they form thick dark storm clouds.

当地球表面附近的热空气开始上升时，它就会冷却。 随着空气冷却，空气中的水分子开始减速并失去能量。 它们收集漂浮在空气中的尘埃颗粒。 这些分子与其他分子结合，形成微小的水滴。 当它们失去能量时，就会变回液体。 这个过程叫做凝结。 这是水循环的下一步。 随着越来越多的水滴聚集在尘埃颗粒上，云就开始形成了。 随着越来越多的水滴形成，云层变得越来越厚。 这些云可以变得非常厚，形成又厚又暗的风暴云。