Science Fair Projects

Ethyl Alcohol vs. E. coli


The objective: My objective is to determine if the amount of Ethyl Alcohol in soap will affect the amount of E. coli killed/removed when washing hands with the soap. My hypothesis is that the more Ethyl alcohol used when making soap, the more E. coli will be killed/removed.


To achieve my objective, I prepared three soaps, each containing 30ml Castor oil, 10ml 40% NaOH, and 100ml saturated NaCl with a different amount of Ethyl Alcohol:10ml,30ml,50ml. To test each soap I soaked my hand in E.coli suspencion then washed my hands with one soap. After washing, I blotted my hand on one sheep blood agar plate (commercially made). I repeated this process with the two other soaps and incubated all plates at 35°C for 24 hours. I used antibacterial soap in between the process to avoid carry over of bacteria present.


All plates had almost the same amount of E. coli growth. The average growth of E. coli for the 30ml soap was 1 colony, the 50ml soap was 1 colony, and the 10ml soap was 2 colonies.


After several tests and observations I was able to determine that the amount of Ethyl alcohol in each soap did not affect the amount of E. coli killed/removed, proving my hypothesis incorrect.

This experiment tests whether the amount of Ethyl alcohol in soap affect the amount of E. coli killed/removed when washing hands?

Science Fair Project done By Justin A. Sotomayor


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