Name:
Date:
Period:_________
Elephant’s Toothpaste!
Alternative Lab Assignment
Due to either being absent from class on October 6, 2015, and/or not having your signed
Hampton District One Science Safety Contract on file, you missed a lab that is worth a major
test grade this quarter. The following is the assignment you must complete by October 12,
2015 to replace that lab assignment.
Introduction:
Millions of chemical reactions, like cellular respiration, are occurring in your body all the time. Hydrogen
peroxide, H2O2, is a toxic (poisonous) by-product of respiration. Most living things, including yeast, contain
an enzyme that helps the breakdown of hydrogen peroxide into other substances that are not poisonous. The
reaction between hydrogen peroxide and yeast is similar to the breakdown of hydrogen peroxide that can
occur in the cells of your body.
2H2O2
2H2O + O2
Question: What happens when yeast is added to hydrogen peroxide?
EXPLANATION:
When yeast goes through the process of cellular respiration, some unintended hydrogen peroxide is
produced. Since this is toxic to the cells, it must be quickly converted into other, less dangerous, chemicals.
Hydrogen peroxide is broken down using an enzyme (protein) called catalase. It is called catalase because it
works as a ‘catalyst’ (or a helper) in this reaction. A catalyst is a substance that speeds up the rate of a
chemical reaction without changing its products.
Humans, too must de-toxify hydrogen peroxide produced in the process of our metabolism. We, too use
catalase for this purpose. Under normal conditions, the breakdown of H2O2 happens very slowly in our cells.
In this experiment, the yeast is added to the hydrogen peroxide to speed up the reaction. The catalase in the
yeast speeds up the process of breaking down the H2O2 and produces O2 and H2O more quickly. The oxygen
gets trapped by the dishwashing detergent as many tiny bubbles.
That is also why H2O2 foams when poured onto a cut: the catalase in our tissues breaks the H2O2 down in to
water and oxygen.
Go to the following web site and watch the 4 minute video. This explains the lab we did in class.
https://sciencebob.com/fantastic-foamy-fountain/
Questions:
1. What is an enzyme?
2. What function does an enzyme have?
3. If the reaction of hydrogen peroxide and yeast, which substance is the enzyme?
4. What toxic product is produced during cellular respiration?
5. What is a catalyst? Which enzyme do we have to help break down Hydrogen peroxide?
6. What is hydrogen peroxide broken down into?
7. Which yeast is added to hydrogen peroxide, the temperature increased. What do we call this type of
reaction? What happened to the energy in the reaction? What do you think caused this temperature
change?
8. If the hydrogen peroxide and yeast was an endothermic reaction, what would have happened to the
temperature?
9. How does pH affect a chemical reaction? An enzyme used in a reaction?
10. How does temperature affect a chemical reaction? An enzyme used in a reaction?
11. Concentration is a very important part of this reaction. The hydrogen peroxide used was a 20% solution –
meaning that 20% was hydrogen peroxide while 80% was water.
a. What would happen to the reaction if we decreased the concentration to the hydrogen
peroxide to 1% or 2% (this is the concentration you get at the store)?
b. What would happen to the reaction if we strengthened the concentration to 60%?
12. Explain what you think would happen if you added more soap? Didn’t add any soap?