Hand Washing Lab Report

Hand washing lab report.

Soft Soap and Bacteria

January 22, 2010



Problem: The purpose of this investigation is to determine which Soft Soap brand works the best against bacteria.

Hypothesis: If the Pink Grapefruit Soft Soap is used when washing your hands, then it will remove the most bacteria because of its fragrance.


·         Soft Soap Milk Protein and Honey

·         Soft Soap Pink Grapefruit

·         Soft Soap Black Raspberry and Vanilla

·         Agar Plate

·         Pencil

·         Paper

·         Sharpie


1.      Outline the plate in four sections and label.

2.      Put bacteria on hands by touching everything.

3.      Wash hands with Soft Soap then touch the corresponding section of the agar plate with the pointer finger.

4.      Repeat Steps 2 and 3 for the rest of the types of Soft Soap.

5.      Record data.

Independent Variable: Fragrance/type of soap

Dependent Variable: The appearance of bacteria

Control Group: The section of the Agar plate that will be unaffected

Control Variables: Same hand, things/objects that are touched, amount of soap, amount of time when washing hands, the use of hand sanitizer before each test.


            The Soft Soap brand has many different fragrances from Juicy Watermelon to Milk Protein and Honey.  They are claimed to all work the same, but with different aromas when using them.  So, which one actually works the best against bacteria?  Bacteria are found everywhere, and are the most simplest of creatures only knowing how to eat and reproduce.  Most of the bacteria are the good kind that coat our skin and live in us to fight off the bad bacteria (NOVA).  The bad bacteria can cause illnesses and diseases by entering the body.  When someone touches an object infected with the bad bacteria and then they touch their mouth, nose, or eyes, the bacteria can enter the body and multiply.  Now one bacterium can become thousands. 

Bacteria reproduce asexually meaning they only need themselves.  They reproduce by binary fission, which is the cell increases its mass, copies its chromosomes, and then finally splits creating an exact copy of itself (Today).  The bacteria have exponential growth which would be 1,2,4,8,16… and so on(Today).   The bacteria continue the exponential growth until there isn’t enough space.   In a matter of minutes there could be thousands of bacteria.  After the growth, they stop and the bacteria pause in the lag phase until they move on to the death cycle. 

For removing bacteria, soap is used.  There are two types of bacteria; the water soluble bacteria, and the not water soluble (En-zine).  For example, dirt is easily washed off with water because much of it is water soluble; the water molecules mix with the dirt molecules and rinses right off with the water.  Grease and oils cannot be washed off with water.  Soap is needed to rinse the grease and oils off because it connects these molecules with the water molecules.  In other words, it makes the grease and oil water soluble.

Pink Grapefruit


Milk Protein and Honey


Data and Observations:


Soft Soap Brand

Amount of Bacteria


Pink Grapefruit



Black Raspberry and Vanilla



Milk Protein and Honey

Very Little




Black Raspberry and Vanilla



Black Raspberry and Vanilla





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