Water Cycle Review

Water on Earth is constantly moving and changing. The water cycle is the continuous movement of water from the Earth's surface to the atmosphere and back again. It has been repeating for billions of years, ensuring that life on Earth always has fresh water.

The Four Main Stages

1. Evaporation — the Sun heats water in lakes, rivers, and oceans. The water turns into water vapor (an invisible gas) and rises into the atmosphere. Sweating and wet clothes drying are also examples of evaporation.
2. Condensation — as water vapor rises, it cools down. The cool vapor turns back into tiny water droplets that clump together to form clouds. This is why clouds form high in the sky.
3. Precipitation — when water droplets in clouds combine and become heavy enough, they fall back to Earth as rain, snow, sleet, or hail. The type of precipitation depends on the temperature.
4. Collection — water that falls as precipitation collects in rivers, lakes, and oceans. It also soaks into the ground to become groundwater. From here, evaporation begins the cycle again.

Why the Water Cycle Matters

• It distributes fresh water across the Earth, filling rivers and lakes that people, animals, and plants depend on.
• It cleans water naturally — evaporation leaves behind salts and impurities, so the water vapor that rises is pure.
• It helps control temperature — water takes in and gives off heat as it changes state, which keeps Earth from getting too hot or too cold.
• It connects all environments — water that evaporates from the ocean can fall as rain on a distant mountain.