Purell vs. Liquid Hand Soap: Purell vs. Liquid Hand Soap: which solution is more effective at killing bacteria commonly found on the surface of the hands? Olivia Klenn 9 th grade

Question Which solution will be more effective at killing bacteria commonly found on the surface of the hands: Purell (ethyl alcohol) or Soft Soap Brand liquid hand soap?

Research One of the most common hand-sanitizers, Purell, includes 62% ethyl alcohol and claims to kill 99.99% of bacteria “of most common germs that may cause illness” Soft soap liquid hand soap does not claim to kill 99.99% of bacteria but does state “just add water for a basic clean” Alcohol is claimed to be more effective and faster at killing bacteria than the common chemicals found in normal liquid hand soap and antibacterial liquid hand soap Purell claims to kill germs on contact, but once the solution has evaporated, its ability to kill germs has disappeared Purell claims to have the ability to kill bacteria such as E. coli, Staphylococcus sp., Streptococcus sp., and even Salmonella, most normal liquid hand soaps do not make this claim

Hypothesis If the same dilutions of either ethyl alcohol or liquid hand soap are tested on Escherichia coli and Staphylococcus epidermidis, then the ethyl alcohol (represents the Purell) will be more effective at killing the bacteria.

Materials 32 blank sterile disks 10 agar petri dishes Tube containing Escherichia coli Tube containing Staphylococcus epidermidis 1 ruler Notebook paper, pencil 1 bunsen burner Gloves Ethyl alcohol 1 Soft Soap brand liquid hand soap (not antibacterial) Water 2 graduated cylinders Prongs 1 metal loop 1 Sharpie 1 roll of duct tape

Procedure 1.Ten petri dishes were acquired 2. The Staphylococcus epidermidis was plated on five of these dishes, Escherichia coli was plated on the other five. These dishes were set aside. 3. Two petri dishes were chosen to use as the controls of the experiment, one control was used for each bacteria type (one for Staphylococcus epidermidis, one for Escherichia coli) 4.A graduated cylinder was filled with water. Four blank sterile disks were soaked in this water. 5. Three disks were placed in one of the petri dishes spread apart 6. The bottom of the dish was labeled “control” and the part underneath the bottom of the blank disks were labeled “w” for water. The bottom of the petri dish was then labeled with the date at the time. 7. The same exact thing was done for the other petri dish. The two dishes were then the controls, and they were placed inside a plastic bin at room temperature %, 25%, and 50% Ethyl alcohol dilutions were made with water.

Procedure Continued 9.For each solution, one blank sterile disk was soaked in it. 10. Three disks were placed in a petri dish with Staphylococcus epidermidis. The bottom of the dish was labeled and the parts where the bottoms of the disks were were also labeled 11. Steps 9 & 10 were repeated %, 25%, and 50% liquid hand soap dilutions were made, the dilutions were made by diluting the liquid hand soap with water. 13. For each dilution, one blank sterile disk was soaked in it and placed in a petri dish containing Staphylococcus epidermidis. 14.The dishes were then labeled with the date and the bottom of the dishes were labeled with the dilutions' strength and the fact that the dilutions used were liquid hand soap dilutions. 15. Steps 13 & 14 were repeated exactly 16. Steps were then repeated exactly, but this time the dishes containing the Escherichia coli were used instead of the Staphylococcus epidermidis. The petri dishes were then checked on at 3 different dates, and each time the zone sizes were measured and recorded.

Variables in the experiment Manipulative Variable: the solution, the bacteria Responding Variable: the zone size Control: the two petri dishes that included the blank discs soaked in water

Trends & Analysis -2 petri dishes, one conatining Escherichia coli and one Staphylococcus epidermidis, showed growth on 12/22/11. The zone sizes for the dish containing Escherechia coli with the ethyl alcohol dilutions were 10 mm for the 50% dilution and 5 mm for the 25% while the zone sizes for the Staphylococcus/liquid hand soap were 5 mm for the 50% dilution and 2.5 mm for the 25% dilution -The liquid hand soap's zones were the same as the last date measured when they were measured on 1/12/12. The ethyl alcohol's zones had completely disappeared when they were measured on the date 1/12/12. -The ethyl alcohol dilutions' zones and liquid hand soap dilutions' zones ended up being around the same width for both the dishes containing Escherichia coli and the dishes containing Staphylococcus epidermidsi, which had a width of 5 mm.

Conclusion -Hypothesis: If the same dilutions of either ethyl alcohol or liquid hand soap are tested on Escherichia coli and Staphylococcus epidermidis, then the ethyl alcohol will be more effective at killing the bacteria - Hypothesis was not supported because when zones for the ethyl alcohol and liquid hand soap were measured and analyzed, they on average ended up being around the same width, which was about 5 mm. This shows that the Purell (ethyl alcohol) is just as effective at killing the bacteria commonly found on the surface of the hands as liquid hand soap, but this is only true only shortly after the solution (Purell) is used, because the ethyl alcohol in the Purell immediately evaporates after use. - Biggest difference between the liquid hand soap and ethyl alcohol zones was the fact that the zones around the ethyl alcohol disappeared by the 3 rd date they were measured (1/12/12), while the zones around the liquid hand soap did not change at all by 1/12/12, showing one that in the long-run, liquid hand soap is more effective at cleaning the hands and killing the bacteria, making it the better solution to use for hand washing. -Data shows us that the ethyl alcohol only works at killing bacteria for a short amount of time, because the ethyl alcohol, which kills the bacteria, eventually evaporates, while the liquid hand soap actually attaches to the bacteria and permanently removes it from the surface, keeping the zones the same size throughout the experiment. -One way to improve this experiment is by doing more trials and maybe even using other types of bacteria.

Works Cited N.p., n.d. Web. 26 Jan N.p., n.d. Web. 28 Feb N.p., n.d. Web. 28 Feb N.p., n.d. Web. 28 Feb Thank you for listening and being attentive to my presentation.