|
Water:
The Facts
The
Water Cycle
Run and get a glass of water and put it on the table
next to you. Take a good long look at the water. Now
- can you guess how old it is?
The water in your glass may have fallen from the sky
as rain just last week, but the water itself has
been around pretty much as long as the earth has!
When the first fish crawled out of the ocean onto
the land, your glass of water was part of that
ocean. When the Brontosaurus walked through lakes
feeding on plants, your glass of water was part of
those lakes. When kings and princesses, knights and
squires took a drink from their wells, your glass of
water was part of those wells.
|
The earth has a limited amount of water. That
water keeps going around and around and around
and around and (well, you get the idea) in what
we call the "Water Cycle". This cycle is made up
of a few main parts:
•
evaporation (and transpiration)
•
condensation
•
precipitation
•
collection |
 |
Evaporation
Evaporation is when the sun heats up water in rivers
or lakes or the ocean and turns it into vapour or
steam. The water vapour or steam leaves the river,
lake or ocean and goes into the air.
Do
plants sweat?
Well, sort of.... people perspire (sweat) and plants
transpire. Transpiration is the process by which
plants lose water out of their leaves. Transpiration
gives evaporation a bit of a hand in getting the
water vapour back up into the air.
Condensation
Water vapour in the air gets cold and changes back
into liquid, forming clouds. This is called
condensation. You can see the same sort of thing at
home... pour a glass of cold water on a hot day and
watch what happens. Water forms on the outside of
the glass. That water didn't somehow leak through
the glass! It actually came from the air. Water
vapour in the warm air turns back into liquid when
it touches the cold glass.
Precipitation
Precipitation occurs when so much water has
condensed that the air cannot hold it anymore. The
clouds get heavy and water falls back to the earth
in the form of rain, hail, sleet or snow.
Collection
When water falls back to earth as precipitation, it
may fall back in the oceans, lakes or rivers or it
may end up on land. When it ends up on land, it will
either soak into the earth or become part of the
“ground water” that plants and animals use to drink
or it may run over the soil and collect in the
oceans, lakes or rivers where the cycle starts all
over again.
|
|
