Water to Drink/Water Filtration

Water to Drink: Lesson Overview
Students read and listen to stories that highlight the problems of access to clean water around the world. Many children and adults get sick and die each day from drinking contaminated water.  Students are introduced to the concept of filtering water using clay pots. People in many countries use this simple technology to remove particulate matter, bacteria and parasites from contaminated water.  Students use Plaster of Paris and chemical additives to make their own filters and then test their effectiveness. They ultimately engineer recommendation for a filter design based on the data they gather from conducting a series of tests.

1. LA STEM Story:  Water to Drink

Fresh, drinkable water is something most citizens of the United States take for granted. We turn on a faucet and out comes water free from chemicals, dirt, bacteria, and parasites.  In many countries, this is not the case.  After a hurricane destroyed the water supply in Honduras, for example, people had to depend on rainfall and small streams for water to drink. In some countries water is taken from lakes, rivers or streams and is often contaminated.  Read about and watch the stories of people challenged to obtain water to drink here: Water to Drink

It is important to engage students in these stories in order to spark their interest in the unit. Prompt students to ask questions and to note interesting information. You can use questions such as: What interested you in the story? What did it make you think about? What else might you want to learn?

For more information about how students can read the story, go to Reading LA STEM Stories.

Students should record observations or questions in a notebook. See directions for the STEM Notebook here.

2. The following explorations should be done in sequence:

A. Experiments with making carbon dioxide gas

B. Making Plaster of Paris with CO2 bubbles

C. Molding filters

DPercolation Rate

E. Turbidity

3. STEM Challenge for Students

Students have learned how to make a filter using Plaster of Paris, baking soda, and cream of tartar.  They have tested their filters in terms of controlling turbidity and how fast the water can be filtered.  They can extend their learning by testing how bacteria might be filtered or killed in the process of filtering.  In this STEM challenge, students add silver nitrate to the plaster mold materials to embed small amounts chemical that act on bacteria. Using culture media, students can test the effectiveness of their filter.  Here are some suggestions.