| earthcare balloon preparation
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| Fresh Water - A Scarce Commodity
Water makes up about 65% of our bodies. Humans - and all
other animals, as well as plants - require water to live; without it,
we would last less than a week.
Water is a very important part of our lives in many other
ways. It keeps the air, the land, our cities, and our bodies clean.
We brow crops with it, transport goods on it, swim in it, travel on
it and use its power to make electricity. It forms political boundaries,
cleans our dishes and clothes and carries away our wate. It even enriches
our language.
More than 70% of the earth's surface is covered by water.
But of all that water, about 97% is salty ocean water - great for squids,
but hard to process for use by landlubbers like us. Of the remaining
3% of earth's water, more than two-thirds is frozen in glaciers and
polar ice sheets. that leaves less than 1% of the water on the earth
for our use- and most of that is groundwater, stored underground in
porous rock and loose sand and gravel.
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Objective: To demonstrate how
limited resh water is.
Materials: One 4 litre container
and two 250 millilitre (two 1 cup) measuring cups.
Activity: Fill the four litre
contrainer with water. Place it in the front of the room. Imagine
that this represents all the water in the world. How much of the
4 litres do you think represents the fresh water, using a ucp
for measure? [Discuss the percentages of salt water and resh water
described above.]
Now pour 250 ml from the four litre jug into
cup #1. This represents all the fresh water in the world. From
this cup, measure 30 ml (1/8 cup) into cup #2. What's left in
cup #1 represents all the fresh water that is inaccessible because
it is frozen in polar ice caps. The 30 ml (1/8 cup) in cup #2
represents all of the fresh water available to us for drinking
and other uses. [Remind the class that muich of even this little
bit of water lies deep in the earth and is not easy for us to
reach in economical ways.]
Discussion: Where do you find
fresh water? Does it look clean and drinkable?
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