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Drinking Water in Arid Climates

This is an activity on water condensation that illustrates to students how water droplets collect on surfaces under certain circumstances. Students measure condensation formed in their water traps and chart the results over several days. They learn to observe and evaluate experimental results and discuss their conclusions as a group. They also design improved water traps to collect greater amounts of water. A narrative about Native American tradition teaches students that water condensation could be an important source of drinking water in arid climates.

Key Concepts

Atmospheric Science, Water Cycle, Condensation

Program/Collection

Multicultural Classroom Activities  View All »

Duration

2 - 50 minute class period

Audience

3-5

Partners

National Teachers Enhancement Network

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http://btc.montana.edu/courses/aspx/lessons.aspx?TheID=33

water

Topics

Earth Science

Resource Type

Extended Lesson Plan

Format

Website

Updated

1/23/2017

You'll find additional information specific to this extended lesson plan below.

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More Info for this Extended Lesson Plan

Background

Many years ago, Native Americans -- especially those who moved frequently across the Great Plains -- often had problems finding safe sources of drinking water. Many tribes lived in very arid regions of North America that often had few easily available sources of water. Native Americans used to migrate from hunting spot to hunting spot and often were not near a river or lake when they needed water. They watched and learned from animals that condensation was a natural source of good-quality water. Animals know by instinct how to find water and food. In the early morning hours, animals like deer, antelope, and buffalo would lick plant leaves to get water. If the Native Americans did not have containers of water with them, they also had to collect water from natural condensation. This traditional source of water in dry landscapes illustrates that the concept of condensation can be used to recover drinkable water from the atmosphere.

Water has three physical states -- gas, liquid, and solid. The gas phase is often called water vapor. The physical state of water is determined by how fast the molecules that make up water are moving. If the molecules are moving quickly then the water is in the gas phase. As the molecules slow down, the water goes from the gas phase to the liquid phase and then to the solid phase. Water in the water cycle moves from the gas phase in the atmosphere (water vapor) to the liquid phase as rain and the solid phase as snow or ice, and then back into the atmosphere as a gas (water vapor) through the process of evaporation.

The movement from gas form to liquid form is called condensation. In order for water to condense, the water molecules must slow down. One way for the molecules to slow down is to come into contact with a surface that is cooler than the dew point. The dew point is the temperature to which the air must be cooled for condensation to occur. Dew point is related to relative humidity because they both indicate the amount of moisture in the air. When relative humidity is high, the dew point is close to the current air temperature. As relative humidity falls, so does the dew point. When water vapor comes into contact with a surface cooler than the dew point and when a condensation nucleus is present, then the water vapor will change into liquid form. Condensation nuclei are particles such as dust, dirt, salt, smoke particles, etc., around which water molecules collect and form water droplets.

Problem/Purpose

The purpose of this multi-day activity is to give students an introductory understanding of water condensation, humidity, dew point, and the water cycle. Students construct water traps outdoors to collect water droplets from the atmosphere. Using results collected over several days, students chart and discuss daily collection amounts as related to daily temperature readings. They learn that Native Americans imitated indigenous animals by collecting drinking water from condensation formed on local plants.

Author

Theresa Murray
Cultural Consultant - Prarie Band Potawatomi

My name is Theresa Murray. I am a Prairie Band Potowatomi Indian from Topeka, Kansas. I am married to Rober D. Murray Jr., an Assiniboine/Sioux Indian. We live in Poplar, MT. the tribal headquarters of the Fort Peck Reservation. We have three children: Isaac a sophomore who is currently attending Fort Peck Community College in Poplar; Jessie, who just graduated high school in Poplar and will be attending college in Missoula this fall; and Bobby, Robert Murray III is a freshman at Poplar High School. I have taught the 5th and 6th grades in Poplar Middle School for the past five years. Before that I worked at For Peck Community College as a Distance Learning Assistant for three years while I was completing my college education. I worked as City Clerk for the City of Poplar for 9 years until I returned to college and started to work as a Tutor under the CSAP program (Center for Substance Abuse and Prevention Program) for 3 1/2 years then I transferred to the high school and worked 1 year there. I worked full time and attended college full to part time while raising my three children. I am currently completing a Technology in the Classroom Master's Program through Lesley College, Cambridge, Massachusetts. I will complete it in the spring of 2004. I am serving my second term on Poplar's City Council.

Vocabulary

Learner Outcomes

  • Understand the source of condensation formed on various surfaces under certain circumstances.
  • Use water traps to collect water droplets formed by condensation of atmospheric moisture and then discuss their results from repeated collections.
  • Appreciate that native peoples often had to find drinking water from nontraditional sources.

Content Standards

  • Blah

Materials

  • Plastic bowls, such as margarine/butter containers (one/group of 6 students)
  • Small gardening shovels/trowels (to dig small holes)
  • 12-inch squares of plastic wrap, each with small hole punched into center (one/group)
  • 4 – 6 large stones/group (about 2-inch diameter)
  • 6 small pebbles/group
  • Science journals (one/student)
  • Printer paper (one/group)

Lesson Procedures

  • Discuss as a class how Native Americans survived where there was no visible drinking water. Ask students whether they have seen dew on the grass in the morning or water on the outside of a glass of ice on a hot day. Have students walked through grass and gotten their shoes wet? Have they seen water or ice formed on the windows of vehicles or houses? Discuss how the condensation formed. Discuss ideas for a water trap to collect condensation.
  • Divide students into groups of six. Have students predict how much water they think they can collect from a water trap in a single night. Have them write their predictions into their journals.
    • Take students to a protected area outdoors where they can leave their water traps for several days.
    • Have each group dig a small hole and set their plastic container into the bottom of the hole. The rim of the container should be level with the ground surface.
    • At the end of the school day, lay the plastic wrap over the container with the hole in the plastic wrap centered over the bowl. Secure the plastic wrap with the large stones around the edge. You might have to use more stones in a windy area.
    • Carefully set the small pebbles into the middle of the plastic wrap, avoiding the hole in the plastic wrap. The plastic wrap should bend downward into the bowl to funnel any condensation into the bowl.
    • Have students record in their journals the relative humidity and the dew point expected that night. This information might be printed in the local daily newspaper. If not, consult a weather website like Weather Underground's http://www.wunderground.com/US/
    • The next morning, instruct students to remove the rocks carefully from their water trap. Make certain that they funnel any water on the plastic wrap into the plasic container underneath.
    • Ask groups to measure the water in their bowls. They might have to measure it as just one drop or two drops, depending on the amount of condensation during the night. Record the amount in the science journals.
    • Repeat the experiment for four nights. Have students plot the results on the piece of printer paper and in their science notebooks, with days on the x axis and number of drops on the y axis.
    • Gather students into a large class discussion. Have each group present its results. Tape the group graphs on the bulletin board. Discuss the connection between relative humidity, dew point, and amount of condensation. **Note that the experiment will not work unless the air temperature is at or below the dew point temperature for the night.
    • Have students return to their desks and design a better water trap as a group. Have the class select one water trap to test and repeat the experiment with the newly redesigned water trap. If necessary, students can bring materials from home to construct the newly designed water trap. Compare the results from the original design and the new design. Are they the same? Why or why not?

    Conclusions

    • Water droplets form on surfaces during the process called condensation.
    • Several factors affect whether condensation occurs, including atmospheric humidity and temperature.

    Assessments

    • Participation in class discussions
    • Participation in group activities (building water trap, graphing results, designing better water trap)
    • Individual science journal

    Extensions

    • Do research on solar stills and purification of drinking water from salt or polluted water
    • Build a simple solar still

    Resources