Problem Scenario

Broad Question:

What substance kills bacteria most effectively?

Specific Question:

Which substance kills bacteria most effectively; germ-ex, antibacterial soap, rubbing alcohol?


I think rubbing alcohol or antibacterial soap will kill the most germs because although germ-x is said to kill germs, it does not get rid of all residue that is left over. If you have a type of slime with bacteria in it, you need to eliminate the slime to effectively remove all bacteria. Rubbing alcohol seems to be stronger when killing germs, and the antibacterial soap with water will not only kill the bacteria, but also wash it off.

Graph of Hypothesis:



Independent Variable:

Hand Sanitizer, Rubbing Alcohol, Antibacterial Soap

Dependent Variable:

Amount of bacteria left over

Variables That Need To Be Controlled:

Amount of each substance.

Vocabulary List That Needs Explanation

General Plan

I will set up four petri dishes, all having the same amount of bacteria in each. Each petri dish will have their own substance added to it to see how it effects the bacteria; hand sanitizer, antibacterial soap, and rubbing alcohol. The fourth petri dish will have nothing done to it, and the bacteria will grow naturally with no changes.

Potential Problems And Solutions

The bacteria could grow incorrectly
There could be uneven amounts of bacteria instead of an equal amount per dish - inaccurate results

Safety Or Environmental Concerns:

The bacteria could spill in some way, making a mess. It could be harmful because bacteria clearly isn't healthy, which is why it would need to be effectively taken care of with cleaning chemicals.

Experimental Design

1. Grow bacteria
2. Get four petri dishes
3. Make sure all petri dishes are cleaned
4. Add antibacterial soap, hand sanitizer, and rubbing alcohol evenly into each separately.
5. Add an even amount of bacteria to each of the substances
6. Your fourth dish will only have bacteria in it, which is the control
7. Test which one is left with the least amount of bacteria

(add the correct headings from the experimental design page before beginning)

Resources and Budget Table

Data Table

Time Line

Background Research

The issue with hand sanitizer is the fact that even if it does kill the bacteria, it does not get rid of the residue left on your hands. For instance, if you have visible dirt on your hands and you use hand sanitizer, it may kill most of the bacteria. However, it will not get rid of the dirt, which is where the bacteria lives. Because of this, it is less effective. When using soap and water, you are killing the bacteria and washing it completely off your hands; any dirt or substance. By doing this, the bacteria does not have any chance of remaining on your hands. When it comes to which most effectively kills all of the bacteria itself, it is best to go with rubbing alcohol. The rubbing alcohol is the ingredient in soaps and washes that kill the bacteria, while mixed with water they simply wash it off.


ABC News. ABC News Network. Web. 05 Apr. 2012. <>.

Detailed Procedure

After growing enough bacteria that will allow an even amount to be placed in all four petri dishes, I'll be adding in the three substances; rubbing alcohol, hand sanitizer, and antibacterial soap, to the dishes that have not had anything added to them. Each of the substance inside of the dishes should be distributed at an even amount. Then, I will add an even amount of bacteria to each. To see how the bacteria would grow without the effects of the cleaning products, I'll also put the bacteria in a dish as a control, which will not be altered in any way.


Photo List


All Raw Data



Data Analysis



Benefit to Community and/or Science