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Do Hand Sanitizers Work?

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Author: Muriel Gerhard

Grade Level: 8th; Type: Chemistry

Objective:

To determine whether disinfectant sprays or disinfectant soaps are most effective in removing bacteria from one`s hands.

Research Questions:

  • What is bacteriology?
  • What are bacteria?
  • What are some of the characteristics of bacteria?
  • How do bacteria reproduce?
  • What are minerals?
  • What is conjugation?
  • What is spore formation?
  • What are endospores?
  • How are bacteria harmful?
  • How are bacteria helpful?
  • How do we control bacterial reproduction and growth?
  • What are some diseases that are caused by bacteria?
  • What are disinfectants?
  • What are antibiotics?
  • What is soap?
  • What is a disinfectant and how does it work?
  • Are the ingredients of disinfectant soaps and sprays?

On the information level, the student will become acquainted with the world of microbiology. He or she will gain some basic insights related to the bacterial world which surrounds us and start to explore both the dangers and the benefits we derive from this sometimes invisible world which impacts upon us in both constructive and destructive ways. The key question is how we control and utilize these precious resources and use these organisms to our advantage. In this project, the student will examine the relative effectiveness of disinfectants to determine whether the state in which they are used, solid or liquid yields better results or if the state of this matter, solid or liquid, is of little or no consequence.

As for the methodology of this project, this science fair experiment also serves to acquaint students with the essential processes of sciencing such as the importance of the use of a control, of identifying dependent and independent variables, of data collection, of pictorial and or graphic presentation of data and of being able to make better judgments as to the validity and reliability of their findings. They take on the role of scientists and in the process behave as one.

Materials:

  • 5 Petri dishes containing agar (can be purchased from Carolina Biological Inc)
  • Disinfectectant spray
  • Disinfectant soap
  • Regular soap
  • Sterile swabs
  • Paper towels
  • Bleach
  • Camera (optional)
  • Safety equipment

Experimental Procedure:

  1. Gather all the materials which you will need for this project which include a set of 5 Petri dishes filled with agar, the latex gloves, safety goggles, apron, the sterile swabs, bleach, the paper toweling, the regular soap, the disinfectant soap and the liquid disinfectant soap. Include the digital camera if you can.
  2. Copy the Data Chart provided below so that you can readily record your observations.
  3. Start by labeling the Petri dishes, one each, as follows: #1. Control, not opened, and not touched by human hands, #2. Unwashed hands, 3.hands washed with plain soap, #4 hands washed with liquid disinfectant soap, and last but not least #5. Hands washed with solid disinfectant soap.
  4. Select four subjects to assist you by lending you their hands or ask members of your family to help.
  5. Start with subject #1 who will just wet a swab with water, and swab his or her unwashed hands and then transfer the contents of the swab to the Petri dish marked unwashed hands and then seal the Petri dish with tape. Continue with each of the other subjects as follows: subject #2 will wash hands with plain soap and repeat the above swab-Petri dish procedure, subject 3 will wash hands with disinfectant liquid soap and repeat the swab- Petri dish procedure and subject 4 will wash hands with solid disinfectant soap and repeat the swab- Petri dish procedure.
  6. Make certain that all Petri dishes are sealed and place them in a warm place to incubate.
  7. On each day for the next five days, carefully observe the growth of the colonies of bacteria in each of the Petri dishes. If you have a digital camera, take photos of all of the dishes each day and note the dish from which each came and date them. If you are not using a camera, make sketches of each of the Petri dish contents and label and date your sketches.
  8. Using your Data Chart, record and review all of the findings. What do you conclude? What was the control in this experiment? Are you convinced that the data serve to answer your question as stated as the objective? If you took the photos, how substantial is the evidence provided by these photos?
  9. Write up your report. Include the answers to the research questions as well as the definition of terms. Make certain to include your bibliography. You may also want to assess the project and think about what you might have done differently or how you may have extended the project.
  10. Prepare your display charts. You plan to display your Petri dishes, make certain that they are closed and secured with tape. Display a sign, DO Not Open! Good Luck!
  11. Important! To dispose of the contents of the Petri dishes, use bleach.

Data Chart of Daily Observations

Samples
Day#1
Day#2
Day#3
Day#4
Day#5
control
 
 
 
 
 
unwashed
 
 
 
 
 
plain soap
 
 
 
 
 
liquid disinfectant soap
 
 
 
 
 
solid disinfectant soap
 
 
 
 
 

 

Terms/Concepts: Bacteria; Nutrients; Agar; Petri dishes; Disinfectants; Colonies of bacteria; Incubation; Binary fission; Spore formation; Conjugation

References:

  • Miller, Levine, J., Biology, Prentice Hall, Englewood Cliffs, New Jersey 1995 pp.354-379.
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