A. Purpose: Are Microorganisms present in the air?
B. Hypothesis: We think the sealed water will be the same, and the unsealed water will be cloudy from the microorganisms in the air. We also think the sealed soup will be moldy and the unsealed soup will be cloudy from the microorganisms in the air.
C. Materials � Beaker (400-ml) � Chicken bouillon soup � Cotton balls � Graduated cylinder (50-ml) � Hot plate � Labels � Test-tube holder � Test-tube rack � Test tubes (4) � Distilled water
D. Procedures 1. Make a copy of the data table shown on page 10. 2. Add 15 ml of chicken bouillon soup to each of two test tubes. Add 15 ml of distilled water to the remaining two test tubes. Label the test tubes with the date and whether they are water or soup. 3. Place the four test tubes into a beaker that is filled halfway with water. Place the beaker on a hot plate. Allow the test tubes to remain in boiling water for at least 15 minutes. 4. Use a test-tube holder to remove the test tubes from the hot water. Place them in a test-tube rack. CAUTION: Use care when handling the hot test tubes. 5. Quickly seal one bouillon tube and one water tube with cotton balls. Let the other test tubes remain open to the air. 6. Make a hypothesis about what will happen to the test tubes. Write your hypothesis in your journal. 7. After one week, examine the test tubes. Compare the appearance of the test tubes containing soup to each other. Are they clear or cloudy in appearance? Hold them near a bright light source to help you decide. Record your results in your data table. 8. Examine the appearance of the two water tubes. Record your observations in your data table. 9. Carefully observe the odor of each test tube using the fanning method. Record in your data table whether the tubes smell spoiled or have no odor.
E. Data Tube Appearance Odor Soup, Open Clear No odor Soup, Sealed Cloudy Smells like chicken soup Water, Open Clear No odor Water, Sealed Clear No odor
F. Observation: Tuesday October 3, 2000, we started experimenting on the chicken soup and water. We boiled the soup. Then we filled up 4 test tubes with 15 ml of chicken soup and 15 ml of water (2 chicken soup, 2 water). We put them in a heated beaker with boiling water in it for 15 minutes. We sealed one chicken soup and one water with a cotton ball. Then we put all the beakers in a test-tube holder. After one week we examined the chicken soup and water in the test tubes by appearance and odor. We then entered the data in the data table.
G. Conclusion: Our hypothesis was partly wrong. The sealed chicken soup was cloudy and not moldy, and the open soup was clear not cloudy. We thought that the open water would be cloudy but it was clear. We were right about the sealed water staying clear.
H. Questions and Answers: 1. What was the independent variable in this experiment? What were the dependent variables? The dependent variables were the chicken soup and the water, and the independent variables were the microorganisms in the air. 2. Which test tubes represented the control group in this experiment? The unsealed test tubes represented the control group. 3. Make a statement explaining how your data did or did not support your hypothesis? We guessed the opposite of all the test tube results except for the sealed water.
Get your own Free Home Page