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Professor Uses Kitchen Chemistry to Teach Scientific Principles

032403chemistry_dl.jpgBy Jane Nicholson

BOONE–The breakfast table is Sandy Eagle’s chemistry lab.

Eagle, a professor of chemistry at Appalachian State University, uses common kitchen activities to illustrate scientific principles such as kinetics, which determines how fast yolks turn green when eggs are hard-boiled. It’s an effective way to reach students, she says.

“There is a lot of really good chemistry that goes on with food, and it makes chemistry so much more approachable if we talk about food in the context of chemistry, rather than talk about chemistry theoretically on its own,” she said.

She also shared her techniques with middle school teachers in a workshop offered by the university’s Math and Science Education Center. She has developed easy and inexpensive lab projects to teach chemistry without concerns about cleanup or use of toxic materials.

Eagle was recognized by Appalachian in 2002 for her exemplary teaching at the undergraduate level.

Eagle became interested in the chemistry of cooking while teaching at Williams College in Massachusetts. She thought the culinary approach would be a fun way to get students involved in research.

Eggs can be used to teach several chemistry concepts. “It turns out that eggs are really quite cool,” Eagle said. “They have a lot of great chemistry in them.”

For instance, if you want green eggs to go with your ham, just hard boil eggs for a really long time. A kinetic reaction takes place in which the cooked egg white releases hydrogen sulfide gas. The gas reacts with iron in the yolk and forms a green compound around the yolk called iron sulfide.

“That is a indication of how long the egg has cooked. The longer the egg is cooked, the more green around the yolk,” Eagle said.

Place the cooked eggs in an ice-water bath and the kinetic process is stopped, preventing the iron sulfide from forming.

“Cooling the eggs at room temperature vs. in an ice bath brings gas laws of chemistry into play. Kinetics and gas laws are something students have a hard time understanding,” Eagle said. “It’s a nice way to talk about kinetics without the use of any toxic chemicals.”

Poaching an egg at varying temperatures helps illustrate the relationship between temperature and time in kinetics found in the Arrhenius equation. A rule of thumb for the equation states that a 10-degree increase in temperature doubles the reaction rate. For instance, if an egg poaches in 10 minutes at 80 degrees, it should poach in 5 minutes at 90 degrees.

“The equation looks kind of scary, but you can illustrate it with egg chemistry,” Eagle said.

One of Eagle’s undergraduate students is working on a project to make tofu in the lab to teach about protein extraction and protein coagulation, and to illustrate techniques such as filtration and calculating percent yield.

“Often times in introductory chemistry labs we have to filter something and make quantitative measurements and calculations. But it doesn’t relate to something that makes sense to the student. These activities provide context, and they are fun.”

Eagle’s reference books are “The Chemistry of Cooking,” by Harold McGee and “CookWise: The Hows and Whys of Successful Cooking” by Shirley O. Corriher.


Picture Caption: Chemistry Professor Sandy Eagle uses common kitchen activities like boiling eggs to illustrate scientific principles. (Appalachian photo by University Photographer Mike Rominger)