Expert: Walter Hintz - 12/26/2011

Question
QUESTION: My child's science fair project is coming up and he is interested in experimenting with household wipes.  He has these ideas: 1) what brand of household wipes will effectively clean the kitchen; or 2) will household wipes clean kitchen better than a liquid cleaner? I don't know what you think will be easier for him. This is his first individual science fair project (3rd grade). What are your thoughts? Plus, how should he test for bacteria in this project and how does he make sure he does this project/experiment properly so that he gets the most accurate result? Thanks!

ANSWER: Comparing antibacterial cleaners involves growing bacteria and I am not a fan of a 3rd grader doing this unless carefully supervised.
Here is what I would advise.
 Using the wipes would be the easiest
 He will need a way to culture the bacteria. You need culture dishes (petri dishes) and media
 Check with your local college biology department and see if they will give you a couple of plates with media. Your local high school may even have them.

  Once you get the supplies he will have to follow the scientific method
1.State the problem: What kind of wipe will work best on counter tops
2. Make a hypothesis(Good guess as to the answer)  
   Wipe A will kill more germs then wipe B
3. Design an experiment to test the hypothesis
    Wipe the counter with both wipes and then swap them and inoculate the plates (petri dish)
    Keep plates warm for 24 hours and then compare the numbers of colonies on the plates
    (UNDER NO CIRCUMSTANCES MUST THE PLATE BE OPENED NOR THE COLONIES TOUCHED)
4. Draw conclusions
% Make a report stating what was done and stating results

    


---------- FOLLOW-UP ----------

QUESTION: Thanks for your quick reply.  On step 3 you wrote "Wipe the counter with both wipes and then swap them".... does this mean, I wipe 2 different petri dishes, with the wipes, cover and tape the plates?   If this experiment is not advisable for a first timer, what kind of experiment would you advise that would be something similar to this...? Thanks again.

Answer
I should clarify step 3. My typing is bad . Wipe the counters with the treated wipes and then swab them. (not swap) with a sterile swab and then swab the plates, tape them and incubate them. I left out an important step. You should use a 3 third plate,a control plate. Swab an area of the counter that has not been wiped with anything and plate it. This lets you know what was on the counter before any treatment.
As long as precautions are followed and you supervise everything I think there would not be a problem