Did you know that we're using the same water over and over again? The water on the earth today has been there for millions of years. It moves from the earth to the air and back to the earth again through a process called the water cycle.
When you lay a wet towel outside in the hot sun, the towel dries because of evaporation. Rivers, lakes and oceans lose water everyday because of evaporation. That water travels into the air as water vapor and becomes part of a cloud. Through condensation, the water vapor in clouds becomes a liquid (such as rain, snow or sleet) or precipitation. The water then comes back to the earth and the process begins all over again.
Not all precipitation falls into bodies of water. Some rain falls on the ground where it may seep through the soil through a process called percolation. The water eventually reaches underground streams and becomes part of the groundwater system.
The Water Cycle keeps water moving - from earth to air and back to earth.
The Water Cycle keeps water changing - from liquid (rain, river water, groundwater) to gas (water vapor) and even to solid (snow and sleet).
We need to keep the water that we have free of contamination.
Task: Watch the video and read the text after that make the task with the text and your book on page 25, explain:
- How is the water cycle?
- What is evaporation process?
- What is condensation process?
- What is the meaning of precipitation?
- What is the meaning of percolation or infiltration process ?