Understanding Weather The Earth is surrounded by a layer of air called the atmosphere. Weather on Earth is caused by the heating of the air in the lower part of the atmosphere by the Sun. The heating and cooling of the air causes it to move in different ways. This movement of air is called wind. Air also contains water in the form of a gas called water vapor. The heating and cooling of air causes the water vapor to condense into clouds. This can cause it to rain or snow. Weather is always changing. The weather in the morning may be different from the weather in the afternoon. Weather changes from day to day and from season to season. Weather is also different in different places.
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Activity 9.1
