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How Can We Find Out What Is in Water?

Author(s): Nancy P. Moreno, PhD, Barbara Z. Tharp, MS, and Judith Dresden, MS.


Have students conduct this activity in groups of four. Place materials in a central area for each group's Materials Manager to pick up.

Before starting the activity, prepare the “mystery liquid” by adding 10–15 drops each of red, blue and green food coloring to one cup of water. 

Pour about 1 cm of “mystery liquid” into a 250 mL beaker or 9-ounce clear plastic cup for each group.

Teacher Materials

  • 250 L beaker, or 9-oz clear cup
  • Red, green, and blue food coloring
  • Water

Materials per Student Group

  • 250 mL beaker, or 9 oz clear cup containing approximately 1 cm of mystery liquid
  • 1–2 white, round, basket-type coffee filters
  • 2 pairs of scissors
  • 2 rulers

Funded by the following grant(s)

National Institute of Environmental Health Sciences, NIH

National Institute of Environmental Health Sciences, NIH

The Environment as a Context for Opportunities in Schools
Grant Numbers: 5R25ES010698, R25ES06932

Houston Endowment Inc.

Houston Endowment Inc.

Foundations for the Future: Capitalizing on Technology to Promote Equity, Access and Quality in Elementary Science Education