Chemistry students have gone nuts!

by Sara Walsh

October 01, 2009

Which nut has more calories: roasted peanuts or roasted walnuts? The chemistry students were recently asked this same question and completed a lab to find out. Using a homemade calorimeter setup, the lab partners lit a nut on fire and observed how much energy was released. They did this by finding the temperature change of the water in the flask above. They did three trials for each nut to get a sufficient sample size. By the end of the class period, the lab was full of floating carbon pieces and burnt nut smell!

Teamwork--Justine watches for temperature change while the Justin makes sure the nuts stays ignited.

The students then calculated, per gram, how many calories each type of nut held (since the definition of a calorie is the amount of energy needed to raise 1 g of water 1º Celsius). The students had to take into consideration that product labels use the nutritional term “Calorie” (with a capital ‘C’). A Calorie is equal to 1000 calories (scientific unit) or 1 kilocalorie.

After their calculations had been done, they compared their results to the nuts’ product label to check for accuracy. Their numbers varied, but all showed lower calorie levels than the product labels. Students hypothesized that heat energy may have been lost from the set-up to the environment and that a more scientific set-up may reduce the difference.