By Christina H.

The purpose of this experiment was to determine which hand soap/antibacterial
soap was most effective at killing bacteria on the hands, then testing that
soap to see how long it remained effective. To carry out this experiment,
four disks were soaked in 10 ml of four different hand soaps and 10 ml of
distilled water. Five petri dishes were labeled with the soap/control they
would contain. Bacteria was then swabbed onto each petri dish. Then the
soaked disks were placed in the five different petri dishes and sealed and
placed in an incubator at 37 degrees celsius for 48 hours. An average zone
of inhibition for each petri dish was determined, and the most effective soap
was found.
Now it was necessary to determine how long that soap was effective. To do
this, 24 disks were soaked in that soap (4 disks per soap) and immediately
one petri dish with disks was put in the incubator representing 0 hours. The
remaining petri dishes with disks were put in the incubator at 2-hour
intervals going from 2 hrs.-4 hrs.-6 hrs.-8 hrs.-24 hrs.. After 48 hrs all
the petri dishes were taken out. The average zone of inhibition for each four
disks used in every petri dish was determined, and the soap's effectiveness
over time was found.After completing this experiment, it was found that Liquid Dial Antibacterial
Handsoap was most effective in killing bacteria. This soap's effectiveness
over time was tested. It was determined that as more time went by the less
effective the soap became.