التصنيف: الصف الحادي عشر

The amazing thing about water is that it never disappears! It has always been on the move, changing from one state to another, in a cycle that is called the Natural Water Cycle. Are you ready for the ride? Read on.

Raindrops keep falling on my head!
What does rain fall out of? That’s right, from clouds! In fact, clouds are made up of millions of water drops, which fall to Earth when they get too heavy! When the water drops are really cold, they freeze and fall as snow, hail or sleet. The scientific word for water falling from the sky is precipitation.

Precipitation falls in different amounts in different parts of the world. Just because it’s raining where you live doesn’t mean it is raining in the next suburb, or even the next street!

Challenge! Can you think of a country where it rains a lot? What about a country where it rains very little?

Water, water everywhere!
There is one place where most of the rain falls; the oceans! Rain that falls onto land flows naturally downhill, into creeks, rivers and lakes. Do you know where most rivers lead to? That’s right, into the oceans and seas! But water may take other paths as well, like seeping into the soil deep underground, where it is then called groundwater.

The trees join the cycle!
Everyone knows that plants and tress need water too. Trees use their roots to take some of the water out of the soil and transport it to their leaves. Here it is used for the process of photosynthesis to grow and reproduce.

On a hot day, some of the water in plants is drawn out of tiny little holes in the leaves called stomata, becoming water vapour in the air. This process is called transpiration.

Where does the water go?
We’ve talked about how water falls down to earth, but how does water actually get back up into the sky? This is where the sun comes in. The sun’s heat causes water on the Earth’s surface to dry up and rise into the sky as water vapour. This process is called evaporation. Without the sun, the water cycle would come to a complete stop! Next time you boil some water at home, watch the steam evaporating out the top of your kettle!

Completing the cycle!
The water vapour evaporating from the Earth’s surface and transpiring from plants travels very high in the sky, where the temperature is much colder. When the water cools down, the water changes back into liquid water drops, a process called condensation. These water drops join together to form a cloud again!