Lesson 3: Testing the
Waters
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3: Testing Water for
pH, Temperature, Phosphates and Nitrates
What is in the water, besides all those molecules of H2O? To answer this question, you will need to do some chemistry! In this lesson, you will be running chemical tests of water quality on your local source of drinking water and water collected from a nearby stream, river or lake. As you study the quality of this water, you will probably want to further consider the water quality standards and the causes of certain pollutants. We will be comparing our results with those of our partners across the globe, and will be making some decisions about which water characteristics we may want to continue to monitor.
Objectives
In this activity you
will...
- measure pH, temperature, phospates, and nitrates in tap (drinking) water and an outdoor water sample.
- post and evaluate the results of these water quality tests.
- make conclusions about whether the water needs to be cleaned or regularly monitored for these characteristics.
Materials
- pH test paper or test kit
- thermometer
- phosphate test kit
- nitrates test kit (both narrow range 0.1-1 ppm and wide range 1-5 ppm)
- samples of water, taken from the water source of a local stream
- samples of water, taken from students' homes or school water fountain
Your teacher will review your activities from lesson two. From your work in lesson 2, you are already familiar with water test kits. Your teacher will explain the new tests you will use today. The phosphate and nitrate test kits are similar to the test kits used in lesson 2. The temperature reading will need to be taken as the water is collected at its source. The pH should be measured with fresh water samples. Give careful attention to the discussion on accurate readings of the phosphate and nitrate tests. You may want to visit the Chemetrics website to read about the test kits.
Before conducting
the tests, predict whether you anticipate any water
quality problems. In other words, do you expect
your water to be within or outside of the acceptable range
for pH, temperature, phosphates, and
nitrates?
Top
Exploration
1. Before
we test our water, let's take a look at these four water
quality characteristics.
Investigate each
of the links below. Consider what each characteristic
teaches us about water quality. Write down the acceptable
range or "satisfactory level" of each.
2. Based on the information you have found, predict the level of each characteristic for the tap water and outdoor water sample you will be testing. Discuss this with your classmates and write down what you expect.
3. Now it's time to test water for each of the four indicators. Each group of 3-4 students will be given water testing materials for pH, phosphates and nitrates. The water temperature should be recorded by the person collecting the water. You will be testing two water samples: drinking water and outdoor water sample.
Students will test both water samples, record results, and discuss them in their groups.
4. Your
teacher will draw a data table in which each group will
write their results for the water tests. From this group
data, calculate class averages for each of the four tests,
and post the class results on the Eco-Connections
Project Forum.
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pH |
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temperature |
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phosphates |
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nitrates |
How do your results compare to your predictions? What have you learned about your drinking water, and your outdoor water sample?
After sharing your
results on the bulletin board, compare what you found with
the results of your partners across the globe. Compare and
contrast the results found in Russia and the United States.
How are the results similar? How do the results
differ?
Top
Taking
Action
Write a summary of the class results, including the comparison with the other groups. Post your conclusions and final thoughts on the Eco-Connections Project Forum for other students to read. Do any of the results raise concern over water quality? Discuss whether the water source needs to be cleaned or regularly monitored for certain pollutants. If you have an interest in organizing an ongoing effort to monitor the water quality of your stream, river or lake check out these web-sites:
In this lesson, you have learned about three additional chemical indicators of water quality, pH, phosphates and nitrates. In addition to these, the physical property of temperature has an influence on dissolved oxygen. If you have not yet visited the outdoor water source from which your samples were taken, the fourth lesson will provide you with an opportunity to do so.