Big Ideas
Summary
Drinking water passes a variety of required tests. Students will put their own mystery sample solutions to a pH test to determine which one is the actual drinking water.
Engage
Use the Slide Deck notes to prepare for this mystery water activity conducted in Explore and Explain
For this Engage, you will be asking questions to prepare for the Explore and Explain Activity in Explore and Explain.
The activity uses 4 water samples. Only one of the four containers holds potable water, the other solutions are “contaminated” (using common household substances like vinegar, baking soda and household bleach) .
Ask the students the questions on the SLIDE DECK before testing the waters in Explore and Explain.
Explore and Explain
Check out this video that demonstrates how the activity is done: pH Instructional Video
Using the four mystery clear containers (remind students not to taste), students are going to test the water in each container by smelling the water; learning about pH, and then by testing the water with test strips.
Elaborate
Review different water quality reports linked in the MATERIALS tab and SLIDE DECK and see if students have gained more trust in the safety of their drinking water.
Teacher Support
Essential Question:
What does it take for us to drink a glass of fresh, clean, delicious water?
Guiding Questions:
Engage
How can we tell if our water is potable if we can’t see anything in it?
Can we figure out which solution is potable water and which ones are contaminated without tasting?
How do you think the Water Department tests the potable water to determine whether it is safe to drink?
What do we mean when we say clear is not necessarily clean?
Explore and Explain
What can our noses tell us?
What is pH?
What is the average level of pH in potable water?
What causes the pH level change in water?
How can we test for it?
Which container has the drinking water in it? How do we know?
How does a city ensure the safety and quality of its drinking water?
Elaborate
What are the regulated contaminants that a public water system like Philadelphia’s is required to monitor and test for and report to the public every year?
How do we know it is safe?
What other ways does Philadelphia Water Department act to maintain our safe drinking water supply?
What examples do we have that explain what they do when they find unacceptable levels of contaminants in drinking water?
What are some of the challenges and how are they being addressed?
Students will be able to:
Engage
Accurately complete the chart and data analysis.
Use the data from the Water Mystery Data Sheet to determine the tap water sample.
Explore and Explain
Reflect in their Watershed Journal on the key details in the content they have learned so far, and list the questions they still have.
Use chemical tests in order to determine which solution is potable water.
Make a determination as to which unknown sample solution is acid (0-5), neutral (6-8) or alkaline (basic) (9-14) by matching the known values with the values they received by testing.
Individually, write the testing procedure they undertook and explain their findings.
Elaborate
Reflect: Given the complexity that the Philadelphia Water Department is dealing with keeping up with the contaminants in our water supply, what three things will you recommend to your family and community that you and they need to do to prevent more and more contaminants from entering our water supply.
Explore and Explain
5-in-1 test strips with color key
4 samples of liquids in plastic cups marked respectively
4 containers for each group of students
Tap water
Vinegar
Household bleach
Baking soda
Pencils
Safety goggles or glasses
Gloves
Testing the Waters Data Sheet (Attachment 2.5-A)
Preparation:
Create the following solution in the four mason jars (or beakers) before the lesson and label the samples as #1, #2, #3, and #4. Get or make extra copies of color keys so each group has a key.
Drinking water from tap
Acidic solution using tap water diluted with vinegar (950 mL water and 50 mL vinegar)
High chlorine solution using tap water diluted with household bleach (995 mL water and 5 mL bleach)
Hardness/alkalinity solution using tap water with baking soda (980 mL water and 60 g of baking soda)
BASIC WORDS:
Acid noun
Chemical substance that neutralizes alkalis, dissolves some metals and turns litmus red.
Base noun
A substance that, in aqueous solution, are slippery to the touch, reacts with acids and turns litmus blue.
Contaminant noun
a polluting or poisonous substance that makes something impure.
Contaminated adjective
Something (like water) that is impure as a result of an addition of poisonous or polluting substance
Chlorine noun
Chemical used for water purification and in the making of chlorine bleach.
pH noun
In chemistry, pH (power of hydrogen) is a measure of the acidity or basicity of an aqueous solution. Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline. Pure water has a pH very close to 7.
ADVANCED WORDS:
Alkalinity noun
Water’s buffering capacity to resist changes in pH that would make the water more acidic. (The pH of neutral water with zero alkalinity will immediately drop if a weak acid is added. The pH of water with higher alkalinity will change very little or not at all if a weak acid is added)
Chemistry noun
A science that deals with the composition, structure and properties of substances and with the transformations that they undergo.
Turbidity noun
In chemistry, turbidity is a measure of how clear the liquid is.
Accurately complete the chart and data analysis. Use the data from the Water Mystery Data Sheet to determine the tap water sample.
In their Watershed Journal, ask students to reflect on the key details in the content you have learned so far, and describe what you are still wondering about.
Make a determination as to which unknown sample solution (1, 2, 3, or 4) is acid (0-5), neutral (6-8), or alkaline (basic) (9-14 (pH)) by matching the known values with the values they received by testing.
Individually, each student writes up the testing procedure they undertook and explains their findings.
Reflection: Given the complexity that the Philadelphia Water Department is dealing with keeping up with the contaminants in our water supply, what three things will you recommend to your family and community that you and they need to do to prevent more and more contaminants from entering our water supply. Optional: Make a PSA.
PA STEELS
Environmental Literacy and Sustainability
3.4.6-8.G Sustainability and Stewardship: Obtain and communicate information to describe how best resource management practices and environmental laws are designed to achieve environmental sustainability.
Related Standards
NGSS
MS-LS2-1 Ecosystems: Interactions, Energy, and Dynamics – Analyze and interpret data to provide evidence for the effects of resource availability on organisms and populations of organisms in an ecosystem.
ELA W.6.1 Write arguments to support claims with clear reasons and relevant evidence.
Student Materials
Student Worksheet