In this activity (on page 2 of the PDF), learners explore surface tension by adding pennies to cups which are "full" of plain water or soapy water. The surface tension of the plain water allows learners to add many coins to the water before it overflows. In the soapy water, fewer pennies can be added. Learners are encouraged to think about the environmental implications of soapy water, or other pollutants that may affect surface tension. Included on the PDF are two additional activities from the Environmental Chemistry unit in OMSI's Chemistry Lab: Iron in The Environment and Recycling Paper.