34

Go WGo WGo WGo WGo With the Flowith the Flowith the Flowith the Flowith the FlowWATER CYCLEWATER CYCLEWATER CYCLEWATER CYCLEWATER CYCLE

main ideas

PROGRAMPROGRAMPROGRAMPROGRAMPROGRAMSYNOPSISSYNOPSISSYNOPSISSYNOPSISSYNOPSIS

related ideas

backgroundinformation

� When people use water, theyinterrupt the water cycle andmake the water dirty.

� When certain pollutants in the airmix with rainwater, the result iscalled acid rain.

� The water on our planet isconstantly being cleaned andrecycled in a continuousprocess of evaporation,condensation, and precipitation.

Water on our planet flows ina never-ending cycle. Water inoceans, lakes, and rivers iswarmed by the sun and evapo-rates into the air as clean watervapor, leaving salts, minerals, anddirt behind. The water vaporcools and condenses around dustparticles to form clouds. Whenclouds become saturated withwater vapor, precipitation falls assnow, rain, hail, or sleet. Thiswater flows into lakes, rivers, andoceans where it completes thecycle. When the water evapo-rates, the cycle begins all overagain.

Sometimes sulfur dioxideand other pollutants in the air mixwith water droplets in the clouds.The result is acid rain.

SCENE 4 Birth of a River 2:20Forest ranger Ann Marie Fender tells castmember Robin how the Colorado riverbegins: mountain snow and ice melt, flowdownhill because of gravity, and merge toform a river.

SCENE 5 Is It Clean Yet? :30Z checks on his experiment to find out if thewater has been cleaned. He finds thingsprogressing nicely.

SCENE 6 Water Works 2:20A trip to the New York City aqueduct lets ussee how water is collected, processed, andpiped to people in the Big Apple.

SCENE 7 People and Water :40Z�s experiment is a success�he�s cleaned thewater. But does the natural water cycle alwayseliminate the stuff we put into it?

SCENE 8 Acid Rain 3:30Robin visits a lake in the Adirondacks thathas no fish or other animals. Why? The lakecan�t sustain animal life. Some people sayacid rain �killed� the lake.

SCENE 1 Z�s Contraption 2:00Cast member Z shows how the watercycle�s evaporation process cleans water.He boils water, salt, and purple foodcoloring. As water vapor from the heatedmixture is captured and cooled, it turns backinto clean, clear water without the �stuff �Z put in at the start.

SCENE 2 The Water Cycle 1:30An animation follows water�s flow from theocean up into the clouds, down to land,and back to the ocean where it begins thecycle again. And we find out how we fitinto the cycle.

SCENE 3 Oceans Don�t Boil 1:00In Scene 1, Z boiled dirty water to clean it.But he knows evaporated ocean water�goes up� fresh, and oceans don�t boil!He tries another approach to cleaningwater�kind of like nature does it!

vocabulary: cycle, condensation, evaporation, precipitation, aqueduct, fresh water

35

3-2-1 CL3-2-1 CL3-2-1 CL3-2-1 CL3-2-1 CLAAAAASSSSSSROOM CONTSROOM CONTSROOM CONTSROOM CONTSROOM CONTACTACTACTACTACT

BEFORE-VIEWINGBEFORE-VIEWINGBEFORE-VIEWINGBEFORE-VIEWINGBEFORE-VIEWINGDEMONSTRDEMONSTRDEMONSTRDEMONSTRDEMONSTRAAAAATIONTIONTIONTIONTION

MATERIALS� hot plate� 6-8 ice cubes� two 2-qt. metal saucepans� potholder� 1 qt. warm water

1. Show the water cycle in a simpleway. Pour warm water into onepan, put it on the hot plate, andheat until water vapor rises.

2. Place ice cubes in the second pan.Use the pot holder to hold the panabout 3" above the pan on the hotplate.

3. Ask kids to describe what�s hap-pening. (As water vapor rises fromhot water, it condenses on thebottom of the ice-filled pan, thendrips back into the hot waterwhere the cycle starts again.)

Redo the Before-Viewing Demonstration, but this timemix 1/2 cup of salt into the water on the hot plate. Allow thewater to boil for a few minutes while you ask students toexplain why puddles disappear after it rains. (Sun heatingthe ground causes the water to evaporate.) How can saltyocean water produce rainwater that is fresh? (Theevaporation process cleans water. Salt and dirt are left behindas the water turns to vapor.)

Now direct kids� attention to the boiling salt water. Pointout the white crust along the edge of the pan. What is it?(salt) Now hold the ice-filled pan over the boiling water for afew seconds, then have a student volunteer to rub his/herfinger across the water that collects on the bottom of the panand taste the water. Is it salty? (no) Why not? (Evaporatedwater vapor is fresh; the salt was left behind.)

AFTER-VIEWINGAFTER-VIEWINGAFTER-VIEWINGAFTER-VIEWINGAFTER-VIEWINGACTIVITYACTIVITYACTIVITYACTIVITYACTIVITY

TUNING INTUNING INTUNING INTUNING INTUNING INAsk kids if they would ever want to drink the water left in the tub after theyshowered or bathed. Why not? (dirty; has soap in it) Explain that there�sonly so much fresh water on Earth and that it�s constantly being recycled.So someday they may be drinking the water they showered with today�orwater that a dinosaur washed in long ago! Invite kids to watch the video tolearn more.

LESLESLESLESLESSSSSSON ONEON ONEON ONEON ONEON ONE

36

LESLESLESLESLESSSSSSON TWOON TWOON TWOON TWOON TWO 3-2-1 CL3-2-1 CL3-2-1 CL3-2-1 CL3-2-1 CLAAAAASSSSSSROOM CONTSROOM CONTSROOM CONTSROOM CONTSROOM CONTACTACTACTACTACT

To have studentsobserve and recordhow fast waterevaporates.

PURPOSEMATERIALS(per 3 students)� 3 plastic cups� plastic beaker that

measures millilitersby tens, or a plasticmeasuring cup

� marker� about 1/4 liter tap water� pencil

WHAWHAWHAWHAWHAT TO DOT TO DOT TO DOT TO DOT TO DO:::::1. Divide the class into groups of 3, then distribute

the materials.2. Have one group member measure 50 milliliters (or

1/4 cup) of water into each cup, marking the waterlevel by drawing a line on the outside of the cup.(Figure A)

3. Tell the class that they will be observing evapora-tion and looking for conditions that affect howquickly or slowly water evaporates. Have groupsget together to decide where to place three cupsof water. Suggest possibilities such as: on a sunnywindow sill, next to a heater, fan, or air conditioner,inside a closed cupboard, and outside in a sunnyand/or a shady spot. Group members might alsoconsider covering the top of one cup with plasticwrap, covering the outside of one cup with blackpaper, testing hot water versus cold water in thesame location, and so on. Students will observehow much water evaporates in each location andmake comparisons.

4. Give each student a copy of the activity sheet, �DisappearingWater,� and ask them to record the location and conditions,amount of water, and start time for each of their group�s cups.Then ask kids to predict which cup�s water will evaporatefastest and slowest, and why they think so.

5. Have a discussion with the whole class in order to decide onthe time interval according to which groups will check theircups of water, pouring what�s left back into the measuringflask to see how much has evaporated. (An interval of about24 hours works well.) After the designated number of hourshave elapsed, have groups measure the water left in each cupby pouring it back into the measuring flask and recording themeasurements on their activity sheets.

How do people cope when water evaporates from oceans,rivers, streams, and reservoirs, but no rain falls to replenishthe water supplies? What rules do people need to follow whenthere�s less and less water available for personal use, for grow-ing things, for factories, and for recreation? Have studentsinvestigate to find out what really happens in extendeddroughts like the California drought of 1990-91. How muststate and city leaders play a part in water conservation? Askkids to suggest other ways help might be given to areas withvery little water. For example, for years some people havesuggested towing icebergs--made of fresh water--todrought-stricken areas of the world. Do kids think this is agood idea? Why or why not?

After kids complete the activity sheets, discuss the ex-periment. Which part of the water cycle did the experimentillustrate? (evaporation) Did location of the cups have anyeffect on how much water evaporated in the set amount oftime? If yes, under what conditions did it evaporate fastest?slowest? Why do you think that is? What happens to thewater after it evaporates? (Water vapor rises and condenses,eventually becomes precipitation that falls back to Earth andinto oceans, etc., completing the water cycle.)

CURRICULUMCURRICULUMCURRICULUMCURRICULUMCURRICULUMCONNECTIONSCONNECTIONSCONNECTIONSCONNECTIONSCONNECTIONS

Ask kids to imagine how it must feel to live in a drought- strickenarea. Have them write a paragraph or two about the things theymust do to conserve water, and how they feel as the droughtgoes on and on.

SOCIALSTUDIES LANGUAGE

ARTS

37

Name: Date:

Predict:Which cup�s water Which cup�s water will evaporate fastest? will evaporate slowest?

Why do you think so?

○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

Describe where cup B is:

Date and time Started:

Date and time Ended:

Amount of water that evaporated:

Is it covered?

Amount of water:

Amount of water:

Describe where cup A is:

Date and time started:

Date and time Ended:

Amount of water that evaporated:

Is it covered?

Amount of water:

Amount of water:

Describe where cup C is:

Date and time started:

Date and time ended:

Amount of water that evaporated:

Is it covered?

Amount of water:

Amount of water:

3-2-1 CLASSROOM CONTACT© 1993 Children�s Television Workshop

TM