Soap vs. Sanitizer
Laboratory Experiment
Why wash your hands?



Hand are the most
frequent transmission
route for many types of
infections.
Pathogens may enter
through the mouth, nose,
or eyes.
Proper hand hygiene is the
easiest way to reduce
infections.
How do you wash properly?


Scrub your hands with soap
and warm water for 20
seconds to 2 minutes.
Scrubbing your hands
physically removes dirt and
grease, which wash away
with the water
What about hand sanitizer?



When water is not available, hand sanitizer can be an
effective alternative.
The alcohol in hand sanitizer disrupts the coating on
bacteria and viruses.
Use enough sanitizer to keep your hands wet while
you rub for at least 30 seconds.
Soap vs. Sanitizer Experiment

Problem/Question:


Which is more effective at reducing the amount of bacteria
on hands: washing with soap or antibacterial sanitizer?
Hypothesis & Prediction:

If washing with soap and water is more effective at reducing
the amount of bacteria on hands, then the soap treatment
will show a greater reduction in bacterial growth than the
sanitizer treatment.
Experimental Design

Independent/Manipulated Variable:


Dependent/Responding Variable:



Soap
Sanitizer
Control:


Bacterial growth
Treatments:


Cleanser/Chemical
No soap or sanitizer
Analysis:

Compare percent reduction in bacterial growth
Methods
Label your Petri dish



Group
#Treatment
Before/After
Before
After

Methods

How to sample:
Methods

Apply treatment for 30 seconds
Analysis



# Before - # After = Difference
Difference ÷ # Before = Reduction
Reduction x 100 = % Reduction
TREATMENT
Before
Number of Bacterial Colonies
After
Difference
% Reduction
Control 1
Control 2
Control Average:
Soap 1
Soap 2
Soap Average:
Sanitizer 1
Sanitizer 2
Sanitizer Average:
Analysis

Sample results:
Number of Bacterial Colonies
After
Difference
% Reduction
TREATMENT
Before
Control 1
119
500
-381
-320%
Control 2
198
32
166
83.8%
Control Average:
-118%
Soap 1
100
68
32
32%
Soap 2
6
90
-84
-1400%
Soap Average:
-684%
Sanitizer 1
7
1
6
85.7%
Sanitizer 2
23
2
21
91.3%
Sanitizer Average:
88.5%
Expected ≈ 0
Expected > 0