More scaffolding

A math activity (5-6) Math-Where is the fresh water? compliments this activity.

Engage/Elicit:

by Flickr user bram app http://flickr.com/photos/bramapp/266010360/ Cannot resolve external resource into attachment. http://creativecommons.org/licenses/by-nc-nd/2.0/

Where do you think the water you drink comes from?

Explore:

The water in the oceans is salty, and you cannot drink it.

[ART: Background Image, Ocean]

1. Most of the water on earth is contained in the world's oceans. In the Drawing Tool below, a giant puddle of water is shown, which represents all the water in the oceans. If all the snow and ice in the world melted into a puddle next to this one, how big would this other puddle be? Next to the graphic of the ocean water, use the Drawing Tool to draw what you think the size of this snow and ice puddle would be in relation to the ocean. Refer to Technical Hints to use the Drawing Tool. This stamp represents the amount of salt water in all the oceans of the Earth.
2. Now check your prediction. A stamp has been added to the Drawing Tool that represents all the fresh water on Earth. Fresh water makes up less than 4% of all the water on Earth. How does that compare to your prediction?

   [ART: Background image, Ice & Snow]

3. Ice and snow account for less than 2% of the water on earth. How much of the fresh water on Earth is in liquid form? Draw the size of the puddle next to the graphic of the ice and snow puzzle.
4. Now check your prediction. A stamp has been added to the Drawing Tool that represents all the liquid fresh water on Earth, which is found in lakes, streams and under the ground. Although snow and ice only account for less than 2% of all the water on earth, they store the majority of the earth's fresh water (69%). How did the size of the stamp compare with your predicted size?
5. What other forms does the freshwater take?

Explain:

Most of the water on the Earth (over 96%) is in the oceans, seas and bays, and is salty. We can't drink that water, or use it for agriculture, and we don't use saltwater in our homes. That leaves less than 4% of the water for use by humans and many plants and animals. And half of that water is permanently frozen! The fresh water available for human use is limited, and it is important to conserve our fresh water and protect it from being wasted or polluted.

Why haven't we run out of water already? Well, the answer is clouds. Clouds are an important part of the water cycle, a process that recycles water. I helps get water from the ocean back into fresh water we can drink!

Can't be same as 3-4 act 4

• Water vapor, the form of water that is a gas, is released by plants (transpiration) and evaporates from lakes, the ocean and the surface of the Earth.
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  ART

• When conditions are right, water turns back into a liquid in the form of tiny droplets.
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  ART

• As the tiny droplets form, they start to clump together and increase in size. When the droplets are big enough, they fall to the ground as precipitation.
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  ART

Now that you've taken a close look at the water on the earth, why do you say we need clouds?

L5: Write your response in the box below. L4: What part do clouds play in the water cycle? L3: Without clouds there would be no... and we wouldn't have any ... for drinking. L2: Without clouds there would be no (sunshine, rain and snow, oceans) and we wouldn't have any fresh water for drinking. L1: Without clouds there would be no rain and snow and we wouldn't have any fresh water for drinking.

Ed: do we need a stamp, or can we just put a background picture into the drawing tool of freshwater compared to saltwater? I don't see that the student is actively using the stamp. Would it be fun (and instructive) to make some  saltwater like seawater (35 g/l) and have everybody taste it?   Posted by ehazzard at Aug 09, 2007 11:41

Ed: follow-up comment: what if you started with fresh water, then added salt until you couldn't stand the taste, then continued to add salt until it was the same as seatwater? That would be dramatic. How about making this an off-computer activity? For 5-6 the measuring of salt (by volume if a scale is not available)  could be a MATH off-computer activity.They could make bar graphs of how  much salt is added vs results of taste test. Posted by ehazzard at Aug 09, 2007 11:46