Fourth Grade
Worksheets
Clouds and Weather
When you are outside on a very cold day, what happens when you exhale (breathe out)? Your breath makes a small cloud, doesn't it? Your breath has water vapor in it. When warm water vapor is cooled by the colder air outside, it changes into tiny water droplets. It makes a little cloud from your breath. Big clouds in the sky are made the same way.
Water vapor is invisible. It is a part of the air around us. When water vapor is cooled, it changes from a gas back into water. Tiny drops of water in the sky clump together. That is what clouds are. When millions and millions of water droplets gather together, clouds get bigger and bigger. The drops of water get bigger and bigger. They get too heavy to stay up in the clouds. They fall back to earth. We have rain!
On some days in the early morning, water vapor cools very close to the ground. You can see sparkling drops of water on the grass. This is called dew.
On very cold mornings, we don't see dew. We see frost! The water vapor has frozen on the grass.
