Energy Transformation: A Mooverlous Lab with Hydrogen Peroxide

This week my students have been doing various demonstrations representing various digestive organs: Cracker in mouth to demonstrate saliva and amylase, bread and orange juice to represent stomach and hydro-chloric Acid (HCL) and aspirin in vinegar, then transferred to baking soda and water to represent the stomach to the small intestine. Today students demonstrated energy transformation chemical to thermal by using cow liver and hydrogen peroxide. 

All organisms rely on enzymes to catalyze chemical reactions.  An enzyme is a biological catalyst that increases the rate of chemical reaction by lowering the level of activation energy necessary to start the reaction.  In other wards it is the spark that ignites a reaction quickly without needing extra energy to do so. Without enzymes, many of the chemical reactions that occur within living things would proceed to slowly to be useful.  We need these reactions to occur quickly during digestion in order to receive the energy in a timely fashion. Enzymes speed up these reactions by bringing the reactants into close proximity and facilitating their interaction. When hydrogen peroxide (H₂O₂) is added to liver, a chemical reaction occurs which results in the products of oxygen gas (O₂) and liquid water (H₂O) (foam).

It was a smelly lab but students really enjoyed using the probes for the first time. I cut the liver ahead of time so students only had to pour the hydrogen peroxide, swirl, and time the chemical reaction. The temperature spiked very quickly then dropped off slowly. I walked around the stations and asked questions to steer them to the correct answer. They were surprised this occurred until they talked about it together then they determined that the hydrogen peroxide was a catalyst and that it only spiked the temperature because at the end of the reaction the temperature went back down. It was a discrepant event for students. 

This was a great inquiry lab that led students on a journey. It was their first time using the probes and "gross, Mrs. CJ, liver is gross." and liver. After the lab as a class we debriefed and then they wrote up a reflection in their journals.