Rain is part of a very important cycle—the water cycle. The sun shines on the water in the earth, the rivers, the lakes, and the s    15    . The water becomes water vapour(水蒸气). The water vapour rises(上升) w    16    the warm air. It is very c    17    in the sky, The water vapour b    18    clouds. The wind blows the clouds. The cold clouds meets a warm cloud. The clouds grow larger and darker, and the warm cloud becomes water again. It falls from the clouds as r    19    .

Water is very important to living things. Without water there can be no life on the earth. All animals and plants need water.   Man also needs water. We need water to drink, to cook our food and to clean ourselves. Water is needed in offices, factories and schools. Water is needed everywhere.

There is water in seas, rivers and lakes. Water is found almost everywhere. Even in the driest part of the world, there is some water in the air. You cannot see or feel it when it is a part of the air. The water in the seas, rivers and lakes is a liquid. The water in the air is a gas, and we call it water vapor(水蒸气).

Clouds are made of water. They may be made of very small drops of water. They may also be made of snow crystals(晶体). Snow crystals are very, very small crystals of ice. Ice is frozen water. It is a solid(固体). There can be snow and ice everywhere in winter.

Water may be a solid or liquid (液体) or a gas. When it is a solid, it may be as hard as a stone. When it is a liquid, you can drink it. When it is a gas, you can not see or feel it.

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