Graduate Partners in Science Education
Creator
Theresa Marie Lorenzo
Title of Lesson
Our Drinking Water
Intended Grade Level (s)
Primarily Grade 6, possibly Grades 7 and 8
Main objective(s)
This lesson plan was developed to introduce the students to the scarcity of drinking water and possible solutions by which this can be addressed. This will build on previous knowledge of the water cycle and introduce students to the concept of distillation. Students will be introduced to large-scale water purification methods such as desalination and consider their drawbacks and benefits.
Learning Objective(s):
AZ DOE---Grade 6, Strand 3, Science in Personal and Social Perspective, Concept 2
PO 1. Propose viable methods of responding to an identified need or problem.
PO 2. Compare possible solutions to best address an identified need or problem.
AZ DOE---Grade 6, Strand 6, Earth and Space Science, Concept 2
PO1: Explain how water is cycled in nature
15 minutes / Engage
Purpose
Walk students through the scarcity of drinking water available for human use as compared to the total amount of water that can be found on earth.
Materials
· 5 gallon aquarium (fill with water before class begins)
· Tap water
· Measuring cup
· Food coloring
· Ice cube tray
· 2 cups- one with a small amount of sand, the other empty
· Dropper
Instructional Sequence
· Ask the students how much water they think is in or on the Earth and list types of water supplies on the board (oceans, groundwater, rivers, ice caps/glaciers, lakes (fresh and salt))
(Refer to the table in the appendix for exact figures)
· Ask them where we get our drinking water from (general supply) and what percentage it is of all the water on the earth.
· Freshwater lakes, rivers, and groundwater, which make up less than an estimated 1% of the world’s water supply. Students may also point out the connection between glaciers/ice and freshwater: many of the world’s major rivers start from glaciers/ice in mountains.
· Fill the aquarium with water and tell them that this represents all the water in the world.
· Remove 18 ounces of water from the aquarium. Place a few drops of food coloring into the aquarium and tell them this represents the proportion of water that is in our oceans.
· Pour 15 ounces of the water into an ice tray and explain that this represents the water that is in our ice caps/glaciers. Place the ice tray in the aquarium.
· Out of the 3 ounces available, only a fraction is in freshwater lakes or rivers. Place a dropper full of water into a cup or in a student’s hand.
· The remaining water represents groundwater. Pour it into the cup with sand and tell the students that groundwater can be found in the pore spaces of soil or in spaces between bedrock. Not all groundwater is accessible for our use.
· Ask them if they are surprised at how little water on earth is available for drinking and ask them to list possible solutions. Would it be possible to convert different sources of water to drinking water?
20 minutes / Explore
Purpose
Students will gain an understanding of distillation, one way to purify water for drinking, by designing and executing a simple distillation experiment using the setup and extra materials available.
Materials
· Hot Plate (2)
· Beaker (2)
· Tubing (2)
· Stopper (2)
· Small cardboard square with weight (2)
· Ice cubes
· Kool-aid/lemon/oranges
· Table Salt
· waste disposal container
Instructional Sequence
· Before the start of the class, prepare two distillation setups (refer to Figure 1 in appendix)
· Show a video of distillation: https://www.youtube.com/watch?v=N0f73tbGCRE
· Divide students into two groups, one supervised by each volunteer.
· Make available the food coloring, tomatoes/lemon juice/orange juice, and extra salt.
· Under your supervision, the students will design and execute a simple distillation experiment of their own choosing using the distillation setup and materials available.
· Ask the students to write a short description of their experiment.
· Ask them for their predictions. Some examples: What will happen if food coloring is placed in the water before distillation? If you place Kool-aid/lemon juice/orange juice before distillation, will it still be present in the distilled water?
· If the students choose an experiment using the Kool-Aid or juices, have them test for the presence in the distillate by smelling it, not tasting it.
· If time allows, they can have multiple experiments.
Safety
The volunteers should supervise the groups closely, especially when using the hot plate. Make sure they do not taste the distillate!
10 minutes / Explain
Purpose
Students will be able to process their results and connect their experiment to an ecological process.
Instructional Sequence
· Quickly go over the results of both groups if they have different experiments.
· The Kool-Aid, juices, food coloring, and salt represent pollution and contaminants. Simple distillation is enough to get rid of some pollutants, such as the color, but not the flavor. Flavor compounds are volatile and boil off with the water.
· Show a graph of how water is naturally purified through the water cycle (evaporation and precipitation)
· If there is time, share some facts about the history of distillation, the types of different distillers (solar stillers, ship distillers, etc.) and how they are used (from individual use to production of distilled water at a mass scale)
· If there is time, introduce a disadvantage of distillation: water is a source of minerals like calcium, magnesium, and sodium, which help protect against nutritional deficiency.
10 minutes / Expand
Purpose
Introduce another form of water purification to students, which they can compare and contrast with what they learned about distillation.
Instructional Sequence
· Introduce desalination, another form of water purification.
· Talk about the high energy and cost requirement of desalination and how some cities/countries have decided to use it.
15 minutes / Evaluate
Purpose
Students will apply the new concepts that they learned about to a real-life situation.
Instructional Sequence
· Divide students into groups of 3-4. Ask them to list some characteristics of cities/countries where desalination could be an advantage. Would desalination be a valid option for Phoenix or anywhere in Arizona? Why or why not? If not, what are other ways Phoenix/Arizona can deal with potential water shortages?
· Have them report their results to the class.
Figure 1. Estimate of global water distribution, by percentage and amount.
Figure 2. Distillation setup for Explore component. (EPA Water Sourcebooks, Grades 6-8)
Figure 3. Illustration of the water cycle. (http://www.energyroyd.org.uk/archives/4781)