Grade Level: 9th - 12th; Type: Biology
Determine whether the application of Febreze will lower the bacterial count.
- What are microorganisms?
- What are bacteria?
- Where bacteria are commonly found?
- What is agar agar?
- Under what kinds of conditions do most bacteria grow?
- Are there useful bacteria? Cite examples.
- Are there harmful bacteria? Cite examples.
- How do we culture bacteria in the lab?
- Why do we refrigerate the petri dishes when they arrive?
- Why do we tape the petri dishes after exposure?
- What precautions should we take to avoid spreading bacteria?
- What is a control and how is it used?
On the informational level, this experiment serves to acquaint students with basic information on the growth of bacteria, their prevalence in our environment, and the conditions under which bacteria can readily grow and multiply. In the process of growing bacteria, the student will have the opportunity to construct his or her own incubator. The student will also learn how to use the scientific method, construct a hypothesis, use a control, identify variables, gather, synthesize and analyze data, formulate a conclusion, and produce a report including a bibliography that documents their secondary research.
- 6 petri dishes containing sterilized, nutrient agar
- plastic gloves
- disinfectant bleach
- a wax pencil
- masking tape
If you do not have access to a school incubator, you can make your own very easily. You will need:
- 20-gallon aquarium
- Heavyweight clear plastic tape
- Small lamp with a 75 watt bulb
- Thermometer (0-100C)
IMPORTANT NOTE: Refrigerate your petri dishes containing the agar when you receive them. Store them upside-down. Make sure the cover is at the bottom and the agar media is on top.
- Gather all the materials you will need for this project.These include the 6 petri dishes, the plastic gloves, the sterile swabs, the bleach, the wax pencil, the plastic bags to discard dirty swabs, the masking tape, and the scissors.If you are not using the school's incubator, you will need the glass aquarium, the clear plastic sheet, the tape, a small lamp, a 25 watt bulb and the Celsius thermometer (0-100). Include a camera if you wish to take photos of the petri dishes containing the bacterial colonies. The colonies can make for interesting photographs.
- Below you will find a data chart. Copy the chart so that you can readily record your observations of the incubated petri dishes.
- Develop your hypothesis. What do you predict will be the outcome of your experiment? How well do you think the Febreze will work? Will it eliminate all of the bacteria? Most? Some? None?
- When ready to start the experiment, take the petri dishes out of the refrigerator and let them warm up to room temperature. This should take about an hour.
- Make 3 copies of the data chart provided below so that you may readily record your observations for each of the three days.
- Put on your apron or lab coat, gloves and safety glasses.
- You will need to either borrow an incubator from your school or make one. To make one, follow these directions: Turn the aquarium on its side so that the opening faces the front. Use the heavy clear plastic to make a hanging door over the opening. Tape it on. Place the 75 watt bulb in the small lamp and place the lamp into the aquarium. Have the cord come out of the front. Place the thermometer inside the aquarium so that you can readily read the temperature without having to move it. Done! The temperature of your incubator should be 32 degrees, or 90 degrees F.
- Using the masking tape and the wax pencil, make labels for the petri dishes identifying the specific location in which they will be placed. For example one on a frequently used couch, one on a bed, and one in the bathroom shower. Make two labels for each: label "B" for before the application of Febreze, and label "A: for after the application of Febreze.
- For both pieces of furniture and the shower head, take a swab and pass it over the surface. Open the corresponding petri dish labeled B (Before Febreze) and swab on the bacteria. Close the petri dish and tape it shut.
- Now, apply a coating of Febreze to the couch, bed, shower head or specific furniture you selected, following the directions provided on the container.
- Using clean swabs, swab each of the locations and transfer the bacteria into the labeled petri dishes. Tape them shut.
- Now, place all six petri dishes into the incubator. You will incubate them for three days, observing each petri dish each day and recording your observations in the data chart provided. You may wish to take photos of both sets of the petri dishes, those before and after the Febreze treatment.
- Write up your experiment. Make certain to include your research in your bibliography. Do not bring your petri dishes to the science fair! Photograph your results before destroying the dishes.
- Put on your safety gear. You will treat your petri dishes with bleach to destroy the bacteria in a ziplock bag. Make sure to soak them overnight before placing everything into the garbage can.
Data Chart: Colony Count
Before – day1
Before – day2
Before – day3
Terms/Concepts: microorganisms; bacteria; agar; incubator
- Lovine, J. Constructing an Incubator, “The Amateur Scientist” in Scientific American. June, 1994 pp.108-111. (This material may be duplicated by teachers for classroom use.)
- Morholt, E, Brandwein, P., Joseph, A., A Sourcebook for the Biological Sciences, Harcout, Brace & World, 1966, pp. 449 – 451.