Always wear eye protection during science experiments. Never handle sharp objects, open flames, chemicals, or other dangerous objects without adult permission and supervision.
This demonstration requires adult help. Never handle hydrogen peroxide without adult permission and supervision.
In this demonstration, we're going to learn about enzymes. An enzyme is a special protein that living organisms use to break down other molecules. Our stomachs have many enzymes used to break down the foods that we eat, for example.
Catalase is an enzyme present in almost all land-dwelling organisms. Its purpose is to break down harmful oxygen-related compounds into its harmless components. These harmful compounds are extremely greedy for electrons, and can end up stealing them from the molecules found in cells. Hydrogen peroxide (H2O2) is one of these harmful compounds––in fact it's often used to kill germs because it can do so much damage to cells.
Because yeast is one such land-dwelling organism, its cells contain catalase to protect against these harmful compounds. By adding yeast to H2O2, we're going to examine the chemical reaction that takes place as the catalase breaks down the hydrogen peroxide into harmless water and oxygen. This reaction is what's called an exothermic reaction because it releases energy in the form of heat.
Place the bowl into a sink or an area that can afford to get a little messy.
With adult permission and supervision, pour the hydrogen peroxide and yeast into the bowl. Immediately measure the temperature of the solution with the thermometer and record the temperature and the time (with seconds) in your notes.
Stir the solution briefly with the spoon and observe. If there are any changes occurring, what do you think they are?
Measure the temperature of the solution every 10 seconds or so and record the time and temperatures in your notes. If you know how, try making a scatter plot of the results. What seems to be happening to the temperature over time?