Science Models

Science Experiments


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.


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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