The True Cost of Clean Water: A General Chemistry Lab

Katie Gulliford, Tacoma Community College

Summary

In this laboratory experiment, students will investigate methods to purify a sample of "dirty" water to drinking water. The students will look at three different methods for purification: distillation, filtration, and iodine (I2) treatment. The students will then calculate the monetary cost of purifying water. The "big ideas" within chemistry are the separation of mixtures and dimensional analysis. The "big ideas" within sustainability are the triple bottom line and social equity.

Learning Goals

The assignment will be a laboratory experiment in which the students purify unclean water to drinking standards. The "big ideas" within chemistry are the separation of mixtures and dimensional analysis. The "big ideas" within sustainability are the triple bottom line and social equity.

Context for Use

Citizens in the United States often do not think about the source and methods of treating water for drinking use. Students are able to go to their tap, turn it on, and have readily-accessible affordable water. Students do not factor the cost of this water into their budget; to them, it is likely free. The purpose of this activity is to have students investigate how water is purified to drinking standards, to calculate the cost of that purification, to investigate the sources of water, and to investigate the separation of matter.

This activity would be appropriate for a general chemistry class, but could easily be modified for introductory chemistry classes.

Timeframe

This laboratory would occur early in the first quarter of General Chemistry (likely the second lab of the quarter).

The first activity will occur during a brief portion of lecture. During the lecture of classification of matter and separation of mixtures, the source of drinking water will be introduced. There will be a demonstration in which water tainted with food coloring is filtered through activated charcoal.

One other activity before the lab begins is to have students track their water usage for a day.

The main portion of the activity will be a laboratory experiment in three parts: distillation, and filtration, and iodine treatment. The students will provide their own source of water from a local source (such as Puget Sound, Snake Lake, China Lake, a local creek, etc).

As a post-lab activity, students will calculate and compare the monetary cost of each type of purification. The students will also investigate the source of their drinking water, as well as look at sources of drinking water in developing nations.

Description and Teaching Materials

The Learning Activities

Much of this is discussed in the "Timeframe".

Again

The first activity will occur during a brief portion of lecture. During the lecture of classification of matter and separation of mixtures, the source of drinking water will be introduced. There will be a demonstration in which water tainted with food coloring is filtered through activated charcoal.

One other activity before the lab begins is to have students track their water usage for a day.

The main portion of the activity will be a laboratory experiment in three parts: distillation, and filtration, and UV radiation. The students will provide their own source of water from a local source (such as Puget Sound, Snake Lake, China Lake, a local creek, etc).

As a post-lab activity, students will calculate and compare the monetary cost of each type of purification. The students will also investigate the source of their drinking water, as well as look at sources of drinking water in developing nations.

Please see the "Student Handout" below.


Student Handout (Microsoft Word 34kB Oct31 11)

Teaching Notes and Tips

Assessment

The main post-lab activities are written in the "Student Handout."

References and Resources

Evergreen State College