Penny Lab: Soap and Surface Tension

Most science classes begin the year with an exercise on the scientific method.  It can be difficult to plan a short activity that will reinforce the main ideas of developing and testing a hypothesis.  This lab is simple and doesn’t require much in the way of materials: pennies, water, and pipettes (and paper towels for clean-up).  Each section of the activity correlates to scientific processes that are discussed in their textbook:  developing a hypothesis, gathering data, analyzing data, communication, and developing further questions.

There is a question about independent and dependent variables, but if you wanted to use this before discussing those details you could help the class with this one during the activity.   Most of my freshman biology students will remember these terms from previous classes.  The final question asks them to pose other questions they might ask about surface tension.  They might wonder, for instance, if other substances can affect the surface tension or if temperature has an effect.  If you have enough time, you could have them develop a new experiment to answer those questions.  Some students may need guidance here, they are usually not comfortable with posing their own questions, likely because most of their experience involves them answering questions that have been posed *to* them.

My AP Biology class does a more advanced version of this activity that includes statistics:  “Investigation: Properties of Water with Statistics

Grade Level: 6-9
Time Required:  15 – 20 minutes

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