The water cycle | Year 7 Physics (Cambridge) PDF Download

The Water Cycle

The water on Earth is constantly moving through a process called the water cycle. The water cycle involves the continuous movement of water from the land to the sky and back again. It ensures that water is recycled over and over.
There are four main stages in the water cycle: evaporation, condensation, precipitation, and collection.

Evaporation

• Evaporation is the first stage of the water cycle. It occurs when the sun heats up water on land, in lakes, rivers, and seas. As the water heats up, it turns into a gas called water vapor. This water vapor then rises into the sky.
• Example: Think about a puddle on a sunny day. Over time, the water in the puddle disappears as it evaporates into the air.

Condensation

• The next stage is condensation. This happens when the water vapor in the air cools down. As it cools, it changes back into small drops of water, forming clouds. Clouds are made up of millions of tiny water droplets.
• Example: On a cold day, you might see your breath. The water vapor from your breath cools and forms tiny droplets in the air, similar to how clouds form.

Precipitation

• After condensation, the water cycle moves to precipitation. This stage occurs when the water droplets in the clouds become too large and heavy for the air to hold. The droplets fall back to Earth as precipitation. Precipitation can be in the form of rain, hail, or snow.
• Example: Rain is the most common form of precipitation. But in winter, if the temperature is low enough, the precipitation might fall as snow.

Collection

• The final stage of the water cycle is collection. When water falls back to Earth as rain, hail, or snow, it is collected in bodies of water like lakes, rivers, and seas. This water will eventually be heated by the sun and start the cycle again.
• Example: Rivers collect rainwater and carry it to lakes or seas. When snow melts, it often flows into rivers and lakes, continuing the collection process.

Summary

The water cycle is a continuous process that moves water from the land to the sky and back again.
It consists of four stages:

• Evaporation: Water heats up and turns into water vapor.
• Condensation: Water vapor cools and forms clouds.
• Precipitation: Water droplets fall as rain, hail, or snow.
• Collection: Water is gathered in lakes, rivers, and seas, starting the cycle over again.