Award Winning Science Fair Project: The 5 Second Rule

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It’s that time again! The time of year that every parent dreads…science fair project time!!

My son brought his science fair paper home last week and lucky for us, this is the first year that it is completely optional for students to participate! Unfortunately for us, he wants to participate in the science fair this year. You might remember that his project from last year, “Is A Dog’s Mouth Cleaner Than A Human’s Mouth”, took first place in the school district science fair, and a silver medal (2nd place) for county. My kids love the taste of victory, and I have to say that we’ve done pretty well with science fair projects around here. We’ve had 3 kids required to do science fair projects over the years and so far all 3 have taken their projects to the district level; two of them have placed 1st in the district and moved on to receive a silver medal for the county! Our youngest son is only in second grade, but he will have big shoes to fill once he is in 4th grade and required to do a project. I still have a couple good ideas that I’m saving for him 😉

Since I already shared last year’s winning project (which you can find here) I thought I’d share my daughter’s 1st place science project from a couple of years ago, where we decided to test out the “5 second” rule.

How many times do we drop food on the floor and quickly pick it up and dust it off while declaring: “5 second rule!” as we pop it into our mouths? We wanted to put that theory to the test and see if there was any truth to it. Is food really safe to eat once it’s fallen on the floor, so long as you pick it up within 5 seconds?

We sampled 3 different foods: a piece of bread, a hot dog, and a tootsie roll. We wanted to see if different textures affected the amount of bacteria that it harbored. The experiment itself was pretty straightforward and simple (I love simple!) but it’s so relevant in our every day living, which is why I think it was a big winner. Below, I will give you the supplies you need, along with directions on how to conduct the experiment.

Supplies:

• 9 Petri dishes and swabs 
• 3 different food items (each food item cut into thirds)
• Sterilized gloves

Procedure:

First, you need your 3 different food items. Like I said, we chose bread, a hot dog and a tootsie roll. We cut each food item into thirds because we wanted to test each item 3 times. You will need to label each of your petri dishes, using 3 for each food item. We labeled the first one as “Hot Dog-not fallen on floor”, the second was labeled as “Hot Dog-after 5 seconds on the floor” and the third was “Hot Dog-after 45 seconds on the floor.” Continue with the same labeling for the other two food items. Basically, we wanted to see if there was a difference between the bacteria content of food that had never fallen on the floor, food that had been on the floor for only five seconds, and food that had been on the floor a bit longer, forty-five seconds.

First, we picked 3 squares on our tile kitchen floor. Just for extra measure, we stepped on each square in our shoes, with the idea that we were spreading around the same bacteria on each square 😉 You probably don’t have to be that obsessive about it, ha ha. We first swabbed each food item that had not fallen on the floor, and rubbed the swab in it’s labeled petri dish (the full instructions on how to properly swab are included in the petri dish kits).

Next, we dropped each food item, one at a time, on the floor for five seconds. We then picked them up, swabbed them and rubbed the swab in the labeled petri dish. We did the same thing one more time, leaving the food on the floor for 45 seconds this time.

The key to culturing your bacteria is to store the petri dishes in a warm, dark place. We stored ours in the laundry room. Each day, my daughter checked on the bacteria growth and took pictures of each dish. She continued this for 3 days and at the end, drew her conclusion about the five second rule. I won’t spoil the results for you; I’ll let you test it out yourselves!

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