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Water Cycle and Global Warming

Water Cycle and Global Warming

Parallel cloud bands over ice floes and melt pools in the Arctic.
Collection of Dr. Pablo Clemente-Colon, National Ice Center, NOAA.

  • Grades:
  • 6-8 9-12
  • Length: Variable

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Overview

Students trace the flow of water in the environment, investigate simulated effects of global temperature change on oceanic surface levels, use data from current models to evaluate the consequences of changes within water cycle, and observe and explain several different properties of water.

This activity is most appropriate for grades 8-12, but it also may be used with other grade levels.


Teacher Background

Life on Earth is dependent on water and variations in its availability. The Earth's hydrological (water) cycle controls the distribution of water, which is always in movement; and always changing states from liquid to vapor to ice and back again. The water cycle is integrated with the complex physical, chemical, and biological processes that sustain ecosystems and influence climate. Ongoing research focuses on human activities that influence the natural distribution system and quality of water within the Earth's systems and to what extent the resulting changes are predictable.

Objectives and Standards

The Interdependence of Organisms

  • The atoms and molecules on the earth cycle among the living and nonliving components of the biosphere.

  • Human activities modify ecosystems.

  • Physical properties of compounds reflect the nature of the interactions among their molecules.

Materials and Setup

Teacher Materials (see Setup)

  • Computer, projector and projection screen 

  • PowerPoint® slides number 13 "Biogeochemical Cycles," and number 14, "Water Cycle."

  • Overhead projector (optional, see Setup)

  • Transparencies of slides (optional)

Materials per Group of Students

  • Computer access for each group member, with four different articles per group preloaded, OR one set of articles listed below (see Setup)

  • Hot plate

Materials per Student

  • Pair of safety glasses and appropriate safety gear for handling liquids and heat

  • Copy of "Why Should I Care" and "3-2-1" student sheets


SETUP

  1. Prepare to project the slides (see Teacher Materials, above) from a computer OR make transparencies of the slides and use an overhead projector.

  2. Demonstration: Assemble the materials listed for the demonstration of "The Three States of Water Demonstration."

  3. Assemble the materials for the "Water Level Investigation" activity.

  4. Access the most recent yearly "State of the Climate Report" from the National Climatic Data Center. Make a PowerPoint® slide or a transparency of "Global Surface Mean Temp Anomalies."

  5. Each student group member will read a different article (below). Have students read the articles online, OR make a photocopied set for each group and distribute before beginning the activity.

  6. If students will read the articles online, pre-load the articles before class.

  7. Have students work in pairs.


Safety

Have students wear safety goggles and appropriate safety gear when heating liquids. Please follow all district and school laboratory safety regulations.

Procedure and Extensions

Time: Two 55-minute sessions.

Engage

  • Project and discuss the "Biogeochemical Cycles" slide to introduce Earth cycles.

  • Follow instructions for "The Three State of Water Demonstration." Begin the activity by conducting Part 1 as a class demonstration.

  • Distribute the activity sheet entitled, "Why Should I Care?" or demonstrate to students how to set up their own paper.

  • Show the "Water Cycle" slide. Ask students (working in pairs) to respond to the questions in column 1 (column 2 is for additional notes and changes later in the lesson). Each student should fill out an activity sheet.

  • Discuss the responses that different groups listed for each question. As the discussion progresses, refer to the diagram. Ask students to add information and questions to think about in Column 2.

  • Conduct Part 2 of "The Three States of Water Demonstration" as a class demonstration.

Explore

Option 1

  1. Have students conduct the "Water Level Investigation" in groups of two. Follow proper safety guidelines when using a hot plate. Make certain that students wear safety goggles and use appropriate safety gear when heating liquids.

  2. Students should notice that ice melting in the container does not raise the water level since ice is less dense than liquid water.

    As water cools, the molecules pack together and it becomes more and more dense until it reaches 4° C. Any attempt to pack them closer together cause the molecules to repel each other; at freezing point, the molecules form a lattice structure, such as ice and snow, which is significantly less dense than liquid water. Ask students, What things in your lives would be different if ice were more dense than liquid water?

  3. Conversely, as water temperature increases, liquid water becomes less dense and expands. Student may or may not observe the water in the container expanding enough to overflow. Ask students, Did you notice water vapor escaping from the container? Did you detect a change in the shape of the water surface? Depending on the air temperature, evaporation rates change. Surface tension is also reduced as water is heated. This is a great time for students to research some of the properties of water.

Option 2

Ask students to design an investigation that will explore how temperature affects water level.

Explain

  1. Present "State of the Climate Report" graph, "Global Surface Mean Temp Anomalies." [Anomaly refers to a deviation from a normal or average and often is used when describing climatic data.]

  2. Based on the results from the "Water Level Investigation," ask students to propose and support ideas about the effect that increasing temperatures might have on ocean water levels. For example, as water temperature in the ocean increases, the volume expands and levels rise. As ice floating in the ocean melts, the level is not raised, however, as surface temperature increases, additional ice breaks off which causes an increase in ocean levels. Ask students to access data from the internet to see if their ideas are supported. (Examples: the IPCC Third Assessment Report, and United Nations Environment Programme: Vital Graphic Series).

    If you only have one computer in the classroom, consider projecting the screen and ask the class to direct the search.

  3. Encourage students to suggest additional factors that influence ocean levels such as movement of the ocean floor, evaporation, subsidence, run off from snow melt, changes in currents, salinity levels and so on. It is important for them to realize that determining the cause of events is not simple.

Elaborate/Extend

  1. Divide students into groups of four. Have each student group member to read of the following articles.

  2. Ask each student to summarize the article they read and share the information with the group. Distribute the "3-2-1 Activity" sheets and have each student to complete it based on all four articles.

Evaluate

Ask each student to create an article or biopolitical cartoon for the school newspaper concerning problems with any of the resources or processes within the water cycle.


Extension

Use the internet to access data on sea level changes, climate changes, and coastal changes. Have students explore questions such as: Is the hydrological cycle (water) changing? Are sea levels changing? Is the climate becoming more variable? Why is Antarctica important to all of us?

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