Name: _________________________
Partner’s Name: _________________
Date: ____________________
Period #: __________________
As the Stomach Churns Lab
Background: In this lab, you will investigate how acid and enzymes affect digesting
food.
Problem: What conditions are needed for the digestion of proteins in the stomach?
Materials:
Beaker
Litmus Paper
3 Graduated Cylinders
Pencil
Pepsin
Water
Boiled egg white
Eyedroppers
6 Test Tubes
Parafilm
Hydrochloric Acid (HCL)
Procedure:
DAY 1:
1. Put on goggles and apron. NOTE: Goggles are to be worn during the entire lab!
2. Send 1 member of each shoulder partner to retrieve a beaker with 6 test tubes
(labeled A, B, C, D, E, F) and pick up a bin with 1 bottle of HCL, 1 bottle of
water, 1 bottle of pepsin, 3 graduated cylinders with eyedroppers (labeled H, P
and W), a piece of parafilm, litmus strips, and a bowl of egg white.
3. Make a minimum of 3 observations of your egg white. Note and record the size,
color and overall appearance of the cubes in each test tube under “Day 1 Egg
White/Liquid Appearance” box in the data table.
4. Partner A: Use the labeled graduated cylinder to add 10 mls of pepsin to test
tube A. Observe the egg white cubes to determine whether any immediate
reaction takes place. Record observations in Day 1. If no change occurs write
“no immediate reaction.”
* NOTE: When changing liquids, make sure to use the correctly labeled
graduated cylinders and eye droppers to prevent cross-contamination.
5. Parnter B: Add 5 mls of pepsin to test tube B. Then add 5 mls of water to test
tube B. Observe whether a reaction takes place. Record results.
6. Partner B: Add 10 mls of HCL to test tube C. Observer whether or not an
immediate reaction takes place. (HCL is dangerous, if you spill it or get it on
yourself notify me immediately!) Record results.
7. Partner A: Add 5 mls of pepsin to test tube D. Then add 5 mls of HCL to test
tube D. Observe whether or not an immediate reaction occurs. Record your
observations.
8. Partner A: Add 10 mls of water to test tube E. Observe whether or not an
immediate reaction occurs. Record your observations.
9. Partner B: Add 5 mls of HCL to test tube F. Then add 5 mls of water to test
tube F. Observe whether or not an immediate reaction occurs. Record your
observations.
10. Stir the contents slightly of each test tube and then find the 6 strips of blue litmus
paper. (Blue litmus paper turns pink in the presence of acid). Dip only the tip of
litmus paper into each test tube. Observe what happens to the litmus paper and
record your observations in “Litmus Paper Day 1.” Partner A: Test tubes A, B,
C Partner B: Test tubes D, E, F
11. Observe the color and clarity of the liquid in each test tube. Record your
observations in the “Egg White/Liquid Appearance Day 1” box in your data table.
12. Over the top of each test tube, stretch the parafilm until you have a tight seal.
You only need a little bit. Label the beaker with your names and period number
and put them off to the side.
13. Fill in hypotheses for test tubes A-F. Make sure they are in the correct format!
Discuss with each other your hypotheses but it is ok to differ on opinion. Use
your knowledge…don’t come up with crazy ideas like the egg will explode!
DAY 2:
1.
Examine the contents of each test tube. Note any changes in the size and
overall appearance of the egg white cubes.
2.
Then test each solution with litmus paper and record your observations in your
data table.
DAY 3:
1. Examine the contents of each test tube. Note any changes in the size and overall
appearance of the egg white cubes.
2. Then test each solution with litmus paper and record your observations in your
data table.
3. Rinse all of the test tubes thoroughly and throw any bits of egg white into the
garbage.
DATA:
Hypotheses:
Test Tube A:
Test Tube B:
Test Tube C:
Test Tube D:
Test Tube E:
Test Tube F:
DATA TABLE for EGG WHITE/LIQUID APPEARANCE
Test Tube
A
B
C
D
E
F
DAY 1
DAY 2
DAY 3
DAY 4
DATA TABLE for LITMUS COLOR
TEST TUBE
DAY 1
DAY 2
DAY 3
DAY 4
A
B
C
D
E
F
Post-Lab Questions:
Answer all questions in complete sentences.
1. Which materials were the best at digesting the egg white?
2. What did this lab demonstrate about the ability of HCl alone to digest food?
3.
What did this lab demonstrate about the ability of pepsin alone to digest food?
4. Why was it important that the cubes of egg white all be about the same size?
5. How did test tubes A and C help you draw conclusion about food digestion in this
investigation? In other words, what does this say about what the stomach needs
to digest food?
6. Why was it necessary to have all 6 test tubes? Explain.