|Difficulty: Intermediate 6|
|Cost ($): 10|
Time required:1 day to prepare, 5 days for experiment
Availability of materials:Easily found
The bacteria should be destroyed before disposal. Pour some bleach into the petri dishes to kill all the bacteria before disposing.
Anti bacterial soap will kill more bacteria than normal soap.
Antibacterial soap contains certain chemicals such as triclosan, which helps kill bacteria. However these chemicals are effective at targeting only some types of bacteria. Since there are many types of bacteria, a particular antibacterial soap may not be effective in killing all forms of harmful bacteria which we come into contact with.
There is growing concern that the overuse of antibacterial soap will cause bacteria to evolve and become immune to the ingredients used in antibacterial soap. Another concern of overuse is that the use of antibacterial soap reduces our own immunity to bacteria because our bodies have not been exposed to bacteria.
In addition, it is interesting that many websites and publications state that it is sufficient to wash our hands and bodies with warm water and ordinary soap to prevent infection.
The materials required for the experiment:
The results show that the antibacterial soap is only effective in killing all the bacteria if the chopstick was washed for more than 2 minutes. If it was washed with antibacterial soap for less than 2 minutes, it was only effective in killing some of the bacteria. Though the non-antibacterial soap also kills the bacteria, it was not as effective as the antibacterial soap.
Use the graph below to plot the results from the table above.
The hypothesis that antibacterial soap will kill more bacteria than normal soap is proven to be true. However the antibacterial soap was effective only if the contaminated object (chopstick) was washed with antibacterial soap for more than 2 minutes.
Many diseases, such as influenza, are caused by viruses and not bacteria. These diseases are not prevented by the use of antibacterial soaps. Washing our hands with warm water and regular soap is sufficient to ward of infections provided that we thoroughly wash our hands, soaping them properly.
The experiment can be repeated by touching the petri plate with a finger instead of using saliva.
Try to repeat the experiment under different room temperatures and/or lighting conditions to ascertain if there is any impact on the rate of growth of the bacteria colonies.
Also consider repeating the experiment with anti-bacterial sprays/hand-rubs.