Summary

In this lesson, students will compare polluted and filtered water to observe how filtering can remove some kinds of pollutants. Students will also be asked to consider how people affect ecosystems and use the scientific method to conduct an experiment on polluted water.

Grade Level

Elementary and Middle School

Objectives

By the end of this lesson, students should be able to

• Use the filtration technique to separate a mixture.
• Compare polluted and filtered water.
• Draw appropriate scientific conclusions given data from a scientific experiment.
• Describe how people can have an effect on the ecosystem.

Chemistry Topics

This lesson supports students’ understanding of

• Separating mixtures
• Physical Properties
• Chemical Properties
• Observations

Time

Teacher Preparation: 15 minutes

Lesson: 20-40 minutes

Materials

Per group:

• 3 cups with lids
• 3 cups without lids
• 1 wax pencil
• 1.5 cups of water
• ½ measuring cup
• 3 coffee filters
• 3 rubber bands
• Pollutants: 10 drops of food coloring, ¼ cup torn paper, 10 drops of vegetable oil, ¼ cup of cut strips of old towel, 10 drops of green dishwashing detergent, and ¼ cup of small pieces of bread.

Safety

• Always wear safety goggles when handling chemicals in the lab.
• Students should wash their hands thoroughly before leaving the lab.
• When students complete the lab, instruct them how to clean up their materials and dispose of any chemicals.
• Do not consume lab solutions, even if they’re otherwise edible products.
• Food in the lab should be considered a chemical not for consumption.

Teacher Notes

• Introduce the lesson by discussing the places we swim and the waterways around us. For example: in Louisiana you could introduce Kistachie National Park, discuss the water we fish and swim in while on a vacation. Introduce Lake Pontchartrain, Mississippi River, and the nearby bayous for discussion.
• Use the suggested websites below to read about and discuss water and air pollution. Some text books in science and social studies also have great, relevant material:
  • What is Water Pollution?
  • What is Air Pollution?

• Monitor student understanding through the experiment.
• Students will filter 3 cups of mixtures, containing different combinations of pollutants to see just what pollutants get extracted.
• Depending on the age and ability level of students, teachers may want to prepare these cups in advance, or allow students to mix the contents themselves.
• Label the first cup “Pollutant 1,” this container will have the ½ cup of water, 10 drops of food coloring and ¼ cup of torn paper.
  • Expect to have some of the coloring get soaked up into the filter and therefore the rest to pollute the water when filtered. The torn paper will also filter out leaving the water cloudy (slightly polluted). This can be filtered more than once to see how much pollution they can get out of it.

• Label the second cup “Pollutant 2,” this will also have the ½ cup water, 10 drops of vegetable oil, ¼ cup of cut strips of old towel to be filtered.
• Label the third cup “Pollutant 3,”this one will have ½ cup of water, 10 drops of green dishwashing detergent, and ¼ cup of small pieces of bread.
  • Expect the green dishwashing detergent to leave bubbles and difficult to filter along with the pieces of bread. The bread begins to break down and create the haze in the bubbles. Pollution.

• Extension Idea: Students can try sand as a filter agent to clean pollution from water. Conduct the same activity on household pollutants such as shampoo or lotion. Vermillion has a wonderful power point that discusses pollution in our waterways and leads into recycle, reduce and reusing material.