Getting a Charge Out of Inquiry

By Eve Pranis

"My fourth graders had finished an electrical unit, and we moved on to growing plants and studying plant needs," said Painted Post, NY, teacher Carolyn Perry. "Then one curious student suggested that since plants have certain needs and since electricity could produce some of those components, such as heat and light, perhaps electrical current would help plants grow better." With support from Dan Fitch, Science Training Specialist in the district, Carolyn's class secured materials to test some "shocking" hypotheses.

The students first brain stormed how to provide electrical current to some pots while leaving an otherwise identical control group shock-free. They decided to plant bean seeds in foil-wrapped pots, treating them equally until they were about two weeks old. The class then chose 16 pots and organized them according to common growth patterns, with eight exhibiting good growth, four exhibiting slow growth, and four exhibiting no growth. In half of each group, students placed zinc and copper plates in the soil, making sure to keep these eight experimental pots from touching the eight control pots.

Next, the attached positive wires to the zinc plats and negative wires to the copper plates, then attached the wires to appropriate terminals on a six-volt battery. Placing a compass near the wired pots, they detected a magnetic field, and using a voltmeter, confirmed that there was electrical current running through the soil. The wired plants all received three hours per day of electric current. Otherwise, they were treated identically to the control plants.

"Although I had never taken on anything like this before," admits Carolyn, "I was pleased with the students' involvement and organization. While we planned the experiment as a class, pairs of students were responsible for measuring, observing, caring for, and recording information on specific plants during the six-week observation period."

Student' observations and records yielded mixed results, and their opinions shifted over time as to what effect, if any, the electricity was having. Although their final results indicated that the electrically treated plants generally had larger, lighter-colored leaves, there were significant inconsistencies in the data, reports Carolyn. Students decided that the results were inconclusive and that further information and experimentation was needed. They brain stormed other factors that might have affected the plants' growth and identified ways they might change their experiment were they to repeat it.

"Students had such pride in what they had done that we invited other school classes in to see and hear about their experiment," reports Carolyn. "It was also a great way to combine both physical and life sciences, but most important, they learned a lot about the precision and time necessary to do real scientific experimenting." As one student's diary entry confirmed, "I didn't know it would take so much time to get ready. I thought it would be easy to set up. Now I know what scientists go through, and I've learned a lot."

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