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, because it contains ethyl alcohol, and ethyl alcohol is proven to kill microorganisms. Most normal liquid hand soaps do not make this claim Two bacteria types commonly found on the surface of the hands are Escherichia coli (gram negative) and Staphylococcus epidermidis (gram positive)

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 Responding Variable: the zone size Control: the two petri dishes that included the blank discs soaked in water Constant: The petri dishes used, room temperature, blank disks used, bacteria type used

Trends & Analysis, Observations -The 50% ethyl alcohol dilutions' zones and 50% liquid hand soap dilutions' zones ended up being around the same measurement when measured on 12/22/11, and this goes for the petri dishes containing Escherichia coli and also the petri dishes containing Staphylococcus epidermidis. The zones' widths averaged at 5mm. -On 12/22/11 the zones of inhibition caused by the 25% dilutions of either solution were close in their diameter measurement, but the liquid hand soap dilution's zone's diameter measurements averaged out to be slightly greater, the same goes for the 12.5% dilutions of either solution -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.

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 ● 50% ethyl alcohol & 50% liquid hand soap= both created an average of 5mm zone diameter on 12/22/11 ● Shows that Purell (ethyl alcohol) is just as effective at killing the bacteria as liquid hand soap, but this is only true only shortly after the solution is used/ applied to the surface

● All zones created by ethyl alcohol dilutions disappeared by 1/12/12 ● All zones around liquid hand soap had the exact same diameter on 1/12/12 as on 12/22/11 ● In long-run, liquid hand soap is more effective at cleaning the hands and killing the bacteria -makes it the better solution for hand washing/cleaning ● ethyl alcohol only prevents the bacteria from growing for a short amount of time ● This is because it immediately evaporates ● liquid hand soap does not evaporate= zone sizes stay consistent throughout experiment ● One way to improve this experiment: do more trials, use 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 to my presentation