- ?Lv 61 0 年前最佳解答
The Water Cycle
Precipitation, evaporation, and transpiration are all terms that sound familiar, yet may not mean much to you. They are all part of the water cycle, a complex process that not only gives us water to drink, fish to eat, but also weather patterns that help grow our crops.
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)
Evaporation is when the sun heats up water in rivers or lakes or the ocean and turns it into vapor or steam. The water vapor or steam leaves the river, lake or ocean and goes into the air.
Water vapor 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 vapor in the warm air, turns back into liquid when it touches the cold glass.
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.
And you thought your parents were OLD
Water is an integral part of life on this planet. It is an odorless, tasteless, substance that covers more than three-fourths of the Earth's surface. Most of the water on Earth, 97% to be exact, is salt water found in the oceans. We can not drink salt water or use it for crops because of the salt content. We can remove salt from ocean water, but the process is very expensive.
Only about 3% of Earth's water is fresh. Two percent of the Earth's water (about 66% of all fresh water) is in solid form, found in ice caps and glaciers. Because it is frozen and so far away, the fresh water in ice caps is not available for use by people or plants. That leaves about 1% of all the Earth's water in a form useable to humans and land animals. This fresh water is found in lakes, rivers, streams, ponds, and in the ground. (A small amount of water is found as vapor in the atmosphere.)
Each part of the cycle drives the other parts.
Water is constantly being cycled between the atmosphere, the ocean and land. This cycling is a very important process that helps sustain life on Earth.
As the water evaporates, vapors rise and condense into clouds. The clouds move over the land, and precipitation falls in the form of rain, ice or snow. The water fills streams and rivers, and eventually flows back into the oceans where evaporation starts the process anew. Learn a lot more about this complicated process in concepts.
Water's state (solid, liquid or gas) is determined mostly by temperature. Although water continuously changes states from solid to liquid to gas, the amount of water on Earth remains constant. There is as much water now as there was hundreds of millions of years ago.
- 匿名使用者1 0 年前
I am the invisible gas form of water.
You call me "water vapor."
My body is light enough so that I am flying and rising into the air now.
In the clouds, my friends are gathering and waiting for me over there.
Before long, cold air surrounds me and my body starts to condense.
Because of my heavy weight, I topple in a liquid form of water from the sky to the streams, lakes or oceans.
Going with the flow, I reach Mt. Everest this time and become part of the glacier.
I am frozen in a solid form of water, just like ice.
Next year, when summer comes, my journey will start all over again.參考資料： my draft