Bacterial Growth

The Effects of Hand Washing on Bacterial Growth

Amy Murphy


Are antibacterial soaps better than regular soaps?


    Cell Biology 

  1. All living organisms are composed of cells, from just one to many trillions, whose details usually are visible only through a microscope. As a basis for understanding this concept: 

    Investigation and Experimentation 

  1. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other three strands, students should develop their own questions and perform investigations. 

Experimental Design 


If hands are washed with antibacterial soap, then they will have fewer remaining bacteria than hands washed with regular soap.

Experimental Groups

Students who wash their hands with antibacterial soap.

Students who wash their hands with regular soap.

Control Group

Students who wash their hands with water only.


1Petri dishes with nutrient agar

2. Liquid hand soap - regular and antibacterial.

3. Sterilized cotton swabs.

4. Masking tape to seal and label Petri dishes.

5. Sink for subjects to wash their hands.

6. Graph paper to tape onto Petri dishes to measure bacterial growth.

7.  Camera & tripod to photograph bacterial growth.


1.  Assign groups (A - wash with antibacterial soap, B - wash with regular soap, C - wash with water only)

2.  Wash hands thoroughly for one minute.

3.  Label Petri dish with period, group letter, and table number. (Ex. P.2, Group A, Table 7)

4.  Rub a sterile cotton swab against the palm of subject’s hand for 5 seconds.  Open Petri dish and streak          the agar from side to side twice.  Repeat with each person in your group.

5.  Incubate samples at room temperature for 24 hours.

6.  After incubation, count the number of bacteria colonies and record it in a data table.

7.  Calculate the average number of bacterial colonies for each group.

8.  Repeat steps 5-7 for a total of 5 days.

Data and Graphs


PicasaWeb Slideshow

References - provide links to websites; use APA style for bibliography

Amy Murphy,
Oct 22, 2009, 8:16 PM
Amy Murphy,
Oct 25, 2009, 5:21 PM