Five-Second Rule

[projectmom]

Hi! I am looking for a mentor for my daughter's 5th grade social science project on the "Is the five-second rule a myth?" We understand the concept of setting controls, but are completely stumped when it comes to performing the experiement - what supplies to use; where to get them, etc. Can someone assist me please? Our goal is more to dispell the myth [/u][/u]than to concentrate on they various types of bacteria found by dropping both dry and wet food types on various flooring surfaces. We would certainly appreciate any assistance that you can provide. Many thanks for your help!

[carolinethorn]

Hi Projectmom,

It sounds like your hypothesis is that "Dropped food gets the same amount of germs on it whether it sits on the floor for less than five seconds or more than five seconds". I would try and persuade her to concentrate on testing just the time aspect first and then doing the additional experiments with varying different flooring surfaces and food types later. Then you can do a really well controlled experiment with good statistics that will have a solid conclusion - simple is better to begin with. So choose one food item, cut it in half so you have 2 identical pieces, drop them on the same floor and leave one for less than 5 seconds and one for more. Talk with her about why you will cut the item in half or try to get two items as identical as possible.
Then swab each with an inoculating loop and transfer that to agar plates and leave overnight. Talk about how to swab each item equally well and that aspect of control - maybe you want to time how long you swab for or count the strokes across the item and the plate. You should be able to see colonies growing on a plate after 24 hours in a warm room. I would recommend doing several repeats with the same conditions and growing all of the plates at the same time. Count how many bacterial colonies there are on each plate.
Then you can look at the average number of bacterial colonies for less than 5 seconds and the average for more than 5 seconds. You can also do various types of graphs and charts. One experiment that shows the same number of colonies for less than 5 seconds and more than 5 seconds is not very convincing as it might just have occured like that by chance. But if you do several repeats and they show that overall the number of colonies are the same it would be a much stronger conclusion (or maybe it will be different and the 5 second rule will be true!)

You can get sterile swabs or inoculating loops and pre-made agar plates from various science suppliers - try googling "agar plates science fair". I found this one
http://www.sciencestuff.com/prod/L-s/1042
http://www.sciencestuff.com/ctgy/L-p-Agar
http://www.thesciencefair.com/Merchant2 ... _Code=agar

Hope this helps. Post back as you think through your method some more or need any more help.
Best of luck,
Caroline

[Thescienceguy]

This is a very good topic to study about!
I am not sure if you are familiar with the TV show "Mythbusters". They did this experiment (along some other side experiments) in one of their episodes. Here is a link if you want to take a look at what they did for the experiment and their findings: http://kwc.org/mythbusters/2005/10/myth ... ion_a.html (Near the bottom of page)

There have also been other experiments about this very fascinating myth. Here is one other webpages that you could visit if you are interested:
http://en.wikipedia.org/wiki/Five-second_rule (Under Research)

[projectmom]

Thank you thank you thank you!!! You all have been most helpful. We are beginning our research this weekend with some of the information you guys have provided. When we get a little further along, I am sure we will have additional questions!!! Thanks again! All of your help is most appreciated!!!:D