College Student Instructions For The Decomposition Of Hydrogen Peroxide Experiment

Introduction:

This experiment will investigate the factors that affect the rate of reaction of the enzyme catalyse, an enzyme found in food such as potato and liver. Catalyse is used to remove hydrogen peroxide from cells. The enzyme speeds up the rate of decomposition of hydrogen peroxide into water and oxygen. The reaction is:

Catalyse is able to speed up the process because the enzyme lowers the activation energy of the reaction. This means that the free energy required for the reaction to take place is made smaller by the presence of catalyse. In fact, catalyse is a particularly reactive enzyme. Biological molecules are damaged greatly by free radicals which is effectively what peroxide is. For this reason living cells evolved highly effective enzymes to decompose peroxide into harmless byproducts.

Hypothesis:

Several factors influence the effect of enzymes including concentration, pH, temperature, and the material being consumed by the reaction, called the substrate. Of interest in this reaction, is the effect of varying enzyme availability. Changing the amount of enzyme able to diffuse to the peroxide solution will cause the reaction rate to vary. One would expect the more surface area for the enzyme to leave the potato the higher the reaction rate. This hypothesis will be tested by observing the rate at which oxygen is evolved from the decomposition of hydrogen peroxide with two different sizes of potato cubes and one pureed. The same volume of potato will be used, only the geometry of the potato will be modified.

Materials:

* 450 ml Hydrogen Peroxide

* Water

* 2 Erlenmeyer flasks

* 1 Stopper w/hole

* Surgical tube (18 inches)

* 150mL measuring beaker

* Potato (Have each potato skinned and cut into 4'x4' cubes)

* Stop watch

Student Instructions for experimental setup:

* Organize into groups of 4 or 5 students

* Obtain a full set of materials from your instructor

* Take time to familiarize yourself with each piece of equipment

* Place the delivery tube into the hole in the stopper

* Carefully pour 150mL of hydrogen peroxide from the bottle into your measuring beaker, and add it to one of the Erlenmeyer flasks.

* Next, pour 150mL of water into the other Erlenmeyer flask.

* 1 student should stand ready with the stop watch, and another should student stand ready by the conical flask containing water.

* The remaining students should carefully remove the stopper from the first conical flask, place sixteen 1cm3 cubes of potato, and quickly put the stopper back on the flask, and then put the free end of the delivery tube under the water level in the second flask

* Start the stop watch and to count the bubbles in the second conical flask every minute for five minutes and record it on the Excel spreadsheet.

* Repeat