5 second rule hypothesis

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The five-second rule: designing an experiment.

You can do research at home to test a common belief about food safety

Oops! Is that muffin still safe to eat? The latest DIY Science video tests if the five-second rule is true.

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By Bethany Brookshire

September 13, 2017 at 9:18 am

This article is one of a series of Experiments meant to teach students about how science is done, from generating a hypothesis to designing an experiment to analyzing the results with statistics. You can repeat the steps here and compare your results — or use this as inspiration to design your own experiment. 

Everyone has dropped food on the floor by accident. And if the floor is fairly clean and you’re hungry, you might pick up that food and eat it. You may even say “five-second rule!” as you bend down to grab it. The idea is that the food hasn’t been sitting on the floor long enough for bacteria to hop on board. But does time matter to a microbe?

Our latest DIY Science video examines the bugs on your bologna with an experiment. We’re not the first to tackle falling foods with science. The five-second rule has been tested in several scientific papers. And Mythbusters probed the issue on TV. But you don’t need a lot of money or a laboratory to test this yourself. In this series of blog posts, you’ll discover everything you need — from building an incubator to analyzing the data.

The five-second rule implies that if food is picked up quickly after it’s dropped, germs won’t have time to get on board. To find out if that’s true, we start with a hypothesis — a statement that can be tested. Because the five-second rule involves a specific length of time, we’ll need to compare food left on the floor for different periods of time.

Hypothesis: Food picked up off the floor after five seconds will collect fewer bacteria than food left on the floor for 50 seconds.

To test this hypothesis, we need to pick a food to test. That food should be something that can be easily dropped and easily picked up. And being inexpensive will help, since we’ll be dropping a lot of it. So we picked — bologna!

Our hypothesis compares two time periods, five seconds and 50 seconds. But that doesn’t mean we can test only one piece of bologna for five seconds against one left on the floor for 10 times as long. We also have to find out whether the bologna had microbes on it before it was dropped. Not only that, we have no idea how clean the floor is!

This means we actually need to test six groups, not two. The first is a control , meaning no bologna. This group will test our germ-growing set-up (more on that later) and will let us see how many bacteria grow without the lunch meat or contact with the floor. The second group will grow microbes from bologna straight out of the package (slices that will never have touched the floor).

How clean the floor is might also matter. In the end, I need to drop bologna on two sections of my tiled floor, each for two time periods. One section of floor should be as clean as possible. The other should be good and dirty — but look clean. We’ll drop pieces of bologna on each tiled section of floor, waiting five or 50 seconds before picking any up.

So those are the six groups, or test conditions. But testing each condition only once won’t be enough. This is because the number of microbes on each of the cold cuts will probably vary a lot. To make sure that the experiment represents what might happen to bologna in general, we need to replicate each several times. To find out how many times, I spoke with Iain Sawyer. He’s a cell biologist at Rosalind Franklin University of Medicine and Science in North Chicago, Ill.

There are two kinds of replication that we need to worry about, Sawyer notes: technical replicates and biological replicates.

A technical replication accounts for differences in how an experiment is conducted. For example, each bologna slice will probably produce slightly different results. A slice might be left out slightly longer before being dropped, allowing germs to grow. Or I might not clean my hands perfectly each time, introducing bugs. A biological replication is one that will account for differences in the living world. There are many species of bacteria, for instance, and they may concentrate more in one spot of floor than in another.

The best plan is to repeat the experiment more than once per group over several days, Sawyer says. This ensures we perform the test many times, which addresses the issues in the technical replication. It means we will perform the experiment in different temperatures and at different times. And dropping more than one piece of bologna for each group each day controls for how much the microbes might vary from one spot of floor to another. This should address any biological variation. In total, we will drop six pieces of bologna per group for each of the six groups, spread out over three days. That’s a total of 36 slices of lunch meat.

Just dropping bologna won’t help us discover if our hypothesis was right, though. We need to measure whether the numbers of bacteria change as a result of how long the food spent on the floor. But bacteria are too small to see without a microscope. And even with a microscope, it would be impossible to count all those germs. So we’ll have to grow the microbes — or culture them — into groups large enough to see. Read the next post to learn how to grow your own germs!

Is the five-second rule really true? We’re designing an experiment to find out.

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Is the 5-second rule true? Science finally has an answer.

Step away from the cookie.

It’s a question that never seems to die: Is it safe to eat food you’ve dropped if you pick it up quickly enough?

The good old five-second rule. It’s been the subject of household debates and innumerable science fair projects, with some claiming it’s real and others denouncing it as bunk.

It seems like a simple question, yet science hasn’t always taken it seriously. Fortunately, modern researchers are finally unraveling the nuances behind the five-second rule.

How quickly can bacteria contaminate food?

The key to the five-second rule is understanding how quickly bacteria transfers from the surface of your floor to your food. A lot of other folks have gotten this measurement wrong, says food scientist Donald Schaffner of Rutgers University. Amateur scientific studies and televised “investigations” have confused the issue by relying on experiments that don’t pass scientific muster.

( These leafy greens are the most prone to contamination . )

In fact,   there had been only one other rigorous inquiry into the five-second rule before 2016: a peer-reviewed study by Paul Dawson, a food scientist at Clemson University, in 2007. Dawson and colleagues reported that food can pick up bacteria immediately on contact with a surface—but that study focused more on how long bacteria could survive on surfaces to contaminate food.

That’s why Schaffner and his student Robyn Miranda decided to test a greater variety of food under more diverse conditions.   Experiments they reported in the journal Applied and Environmental Microbiology in 2016 showed that the five-second rule is really no rule at all. They found that the longer food sat on a bacteria-coated surface, the more bacteria glommed onto it—but plenty of bacteria was picked up as soon as the food hit the ground.

( Here's what to do if you see mold on your food .)

The bigger culprit here is not time but moisture. Wet food (watermelon in this case) picked up more bacteria than drier food, like bread or gummy candy. Carpeted surfaces transferred fewer bacteria to food than did tile or stainless steel, since it soaked up the bacterial solution the scientists applied. (But no, the scientists say, that doesn’t mean you should trade in your dishware for throw rugs.)

Since then, more studies have confirmed how easy it is to transfer bacteria in the kitchen, whether on fingers or simply by using the same cutting board for meat and veggies (even when washed between uses). And in 2021, scientists in Indonesia were inspired to debunk for themselves the five-second rule and its Indonesian counterpart, known as belum lima menit , or the five-minute rule.

But is it ever safe to eat food from the ground?

So, if science has so thoroughly debunked the five-second rule, does that mean it’s unsafe to eat food that has hit the floor? That depends on the surface and what kind of bacteria you might pick up. “If you’re in a hospital and you drop something, you probably don’t want to eat it,” Dawson says. Likewise, you certainly wouldn’t want to pick up Salmonella   from a kitchen floor covered in chicken juice.

( Salmonella can be deadly. Here's how to protect yourself .)

But in most cases, eating a cookie that has picked up a little dust and floor bacteria is not likely to harm someone with a healthy immune system. “Ninety-nine percent of the time, it’s probably safe,” he says. Practicing good sanitation by keeping floors and surfaces clean is the most important lesson in all of this.

Still, the five-second rule will likely endure. “People really want this to be true,” Schaffner says. “Everybody does this; we all eat food off the floor.”

Perhaps the value of the five-second rule (or the three-second rule, if you’re more uptight) lies more in psychology than microbiology. If nothing else, having a rule provides a socially acceptable excuse for our unsavory behavior. Just holler "Five-second rule!" before picking a cookie off the floor and popping it into your mouth, and everyone can have a good laugh. It’s a bit like calling shotgun before elbowing your way into the front passenger seat.

And that leaves us with another way to decide whether to eat that jelly bean you dropped: Just see if anyone’s looking.

For Hungry Minds

Related topics.

• SCIENCE AND TECHNOLOGY
• MICROBIOLOGY
• FOOD SAFETY
• IMMUNE SYSTEM

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New Research

What Does Science Say About the Five-Second Rule? It’s Complicated

The real world is a lot more nuanced than this simple rule reflects

Aaron Sidder

Many people of all ages agree: Food, when dropped on the floor, remains “good” for five seconds. But this pillar of American folklore, the so-called “five-second rule,” is now under attack from scientists at Rutgers University .

Though the five-second rule may seem like a silly line of inquiry, food safety is a major health burden in the United States. The Centers for Disease Control and Prevention estimate that every year, one in six Americans (roughly 48 million people) get sick from foodborne illness, 128,000 are hospitalized, and 3,000 die.

“We decided to look into this because the [five-second rule] is so widespread. The topic might appear ‘light,’ but we wanted our results backed by solid science,” Donald Schaffner , food scientist at the School of Environmental and Biological Sciences , told Rutgers Today .

Schaffner and his graduate student Robyn Miranda tested different bacteria transfer scenarios using four surfaces (stainless steel, ceramic tile, wood, and carpet) and four foods (watermelon, bread, bread and butter, and gummy candy).

They inoculated each surface with Enterobacter aerogenes —a nonpathogenic “cousin” of Salmonella bacteria that occurs naturally in the human digestive system—and dropped the food on each surface for differing lengths of time (less than one second, five, 30, and 300 seconds). The food samples were then analyzed for contamination. In total, the different combinations of surface, food, and length of contact yielded 128 scenarios, each of which was replicated 20 times. The pair published their results in the journal Applied and Environmental Microbiology .

The duo didn’t necessarily disprove the five-second rule, showing that bacteria transfer does increase with contact time. However, their findings reveal a more nuanced reality than that imparted in common playground wisdom.

“The five-second rule is a significant oversimplification of what actually happens when bacteria transfer from a surface to food,“ Schaffner said. “Bacteria can contaminate instantaneously.”

By food, watermelon collected the most bacteria, and gummy candy the least. According to Schaffner, moisture drives the transfer of bacteria from surface to food; the wetter the food, the higher the risk of transfer.

Looking at the surfaces, tile and stainless steel had the highest rates of contamination transfer. Somewhat surprisingly, carpet had the lowest rate of transfer, and the rate was variable on the wood surface. In the end, they found that many factors contribute to contamination: The length of contact, the characteristics of the surface and the moisture of the food all play a role.

Schaffner and Miranda are the not the first to investigate the five-second rule, but peer-reviewed research is limited. In 2013, the popular MythBusters duo also found that moist foods collected more bacteria than drier foods, and an undergraduate research project tested the rule in an unpublished 2003 study from the University of Illinois. Interestingly, the Illinois study found that women are both more familiar with the rule than men and more likely to eat food off the floor.

Unsurprisingly, the Illinois researchers also found that cookies and candy were more likely to be picked up and eaten than cauliflower and broccoli, which raises an important question. If we really want that food, does it  matter how long it has been on the floor?

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Aaron Sidder | | READ MORE

Aaron Sidder is an ecologist and a freelance science writer based in Denver, CO. He is a former AAAS Mass Media Fellow whose work has appeared National Geographic and Eos.

Science Friday

• Science Diction
• Best Of 2019

The Origin Of ‘The Five-Second Rule’

It has to do with Genghis Khan and Julia Child.

First Known Use:

The first written reference to a “rule” about the acceptability of eating dropped food appeared in 1995 —but the household guideline was already long in the making.

Whether you call it the five-second rule, three-second rule, or the ____-second rule, you know what this rule is. Someone drops a tasty morsel of food on the ground and scoops it right back up, declaring that, according to the “rule,” there was no time for the bacteria to glom onto the treat. As usual, the history of this idiom is a little more complicated than that, and the science is, too. Is there any scientific validity to the five-second rule?

Genghis Khan, Julia Child, And The Five-Second Rule

The five-second rule as we know it today has murky origins. The book Did You Just Eat That? by food scientist Paul Dawson and food microbiologist Brian Sheldon traces the origins to legends around Genghis Khan. The Mongol ruler is rumored to have implemented the “Khan Rule” at his banquets. “If food fell on the floor, it could stay there as long as Khan allowed,” write Dawson and Sheldon. The idea was that “food prepared for Khan was so special that it would be good for anyone to eat no matter what.”

“In reality,” they write, “people had little basic knowledge of microorganisms and their relationship to human illness until much later in our history. Thus, eating dropped food was probably not taboo before we came to this understanding. People could not see the bacteria, so they thought wiping off any visible dirt made everything fine.”

Roughly six centuries after Khan’s death, germ theory evolved into, as the Encyclopedia Britannica writes, “perhaps the overarching medical advance of the 19th century.” Researchers determined that tiny, invisible microorganisms caused certain diseases and infections—and French chemist Louis Pasteur proved that those same kinds of microorganisms are behind both wine fermentation and the souring of milk. But despite knowing that germs are everywhere, it can still be tough to walk away from a tempting treat that slipped through one’s fingers.

We see the rule pop up once again in a 1963 episode of Julia Child’s cooking show The French Chef , which may have helped canonize the attitude, if not the phrase, into popular imagination. The famous chef attempted to flip a potato pancake in a pan, but she missed, and the pancake landed squarely on the stovetop.

“When I flipped it, I didn’t have the courage to do it the way I should’ve,” Child said. “But you can always pick it up if you’re alone in the kitchen. Who is going to see?”

The flopped pancake sits on the stovetop for about four seconds before Child tosses it back into the pan, but by the time the phrase begins to solidify and appear in print, people take their own liberties with the exact amount of acceptable seconds. According to the Oxford English Dictionary , the first mention in print of some sort of rule came from the 1995 novel Wanted: Rowing Coach , which referenced a “twenty-second rule.” A few years later, in the 2001 animated film Osmosis Jones , a character follows the “ten-second rule” and eats a germ-infested egg, which sends his body’s immune system into disarray.

So, Is The Five-Second Rule Actually Real?

Robyn Miranda, a Ph.D candidate in food science at Rutgers University, published a study in Applied and Environmental Microbiology with her adviser that scientifically investigated the validity of the five-second rule.

“It was not what I expected to do for my master’s,” she says. “We saw this as a really important opportunity to look at this rule that people truly follow, that consumers really use. So, let’s see if this matters, from a public health standpoint.”

Miranda stocked up on four different food types: watermelon, bread, bread and butter, and gummy candy. Then, she methodically dropped each food onto one of four surfaces typically found in kitchens—stainless steel, tile, wood, and carpet—and let each food item sit for exactly less than a second, five seconds, 30 seconds, and five minutes to measure bacterial transmission. Miranda and a team of undergraduates did 20 replicates of each food, on each surface, for each length of time, over the course of six months. “I’m not going to lie; doing the experiments lost its luster after a while,” she says. “But the results were very interesting.”

The Science Behind The Five-Second Rule

Wearing a food seat belt.

While microorganisms are to blame for infections, not all bacteria are created equal.

“We carry four pounds of bacteria around with us on our bodies all the time,” Paul Dawson tells Science Friday.  “And we have more bacterial cells in and on our body than we have our human cells—so we’re kind of in symbiotic relationship with it. And we’re more and more finding they are part of our health, the delicate balance there, so to speak.”

There is some truth to the idea that exposure to certain bacteria and compounds can help build immunity, says Dawson. But we also know that people can become seriously sick from certain infections, so random exposure may not be the best practice. Dawson compares eating food off the floor to wearing a seatbelt: “You probably could do both of those your whole life and never be injured or get sick, but we know with the seat belt that if you have an accident or there is bacteria there, you’re going to be exposed to it.”

“Speaking specifically about the five-second rule and when eating food off the floor, probably in reality there’s not much risk in that,” he says. “But I don’t know if there’s much to be gained either though, as far as immunity.”

But often, it’s not immunity that’s in the forefront of people’s minds when a morsel hits the floor.

“I don’t eat food off the floor, but I also don’t drop food on the floor,” says Robyn Miranda. “But if I [did], it would depend.” Watermelon? No way, she says. Skittles? Maybe. “I guess you’d be surprised what people will do for a food that they care about.”

Sources And Further Reading

• Special thanks to Robyn Miranda and Paul Dawson
• Did You Just Eat That? Two Scientists Explore Double-Dipping, the Five-Second Rule, and Other Food Myths in the Lab by Paul Dawson and Brian Sheldon
• “Longer Contact Times Increase Cross-Contamination of Enterobacter aerogenes from Surfaces to Food” (American Society for Microbiology: Applied and Environmental Microbiology)
• “History of medicine: Verification of the germ theory” (Encyclopedia Britannica)
• The Oxford English Dictionary

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About johanna mayer.

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January 18, 2017

Is the 5-Second Rule True?

Should you really abide by the famous 5-second rule?

By Everyday Einstein Sabrina Stierwalt

Most of us have heard it: if you drop food on the floor, it’s still okay to eat it, as long as you act quickly and pick it up within five seconds of it hitting the ground. But does the so-called “five-second rule” have any scientific backing? Anecdotally, most of us would agree—it depends on the kind of food. I’m more likely to eat a cracker that I’ve dropped on the floor than I am, say, a buttered bagel that lands spread-side down. But does timing also make a difference? Is there really a delay or grace period before which germs can find their way to your fallen food?

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Wonder of the Day #1048

Is the Five-Second Rule Really True?

SCIENCE — Life Science

Have You Ever Wondered...

• Is the five-second rule really true?
• What is the five-second rule?
• Is it ever alright to eat food that has fallen on the ground?
• contaminate ,
• five-second ,
• food-borne ,
• hepatitis ,
• Mythbusters ,
• phenomenon ,
• salmonella ,
• superstition ,

Imagine you’re just about to relax on the couch on a Saturday afternoon. You have a plate full of potato chips…or a hot dog…or a pretzel… to snack on while you watch TV. But on your way to sit down, you trip over something on the floor. Your plate tilts and tosses a fine morsel of food right onto the floor.

What are you to do? You’re so hungry. If you pick it up quickly — within, for example, five seconds — shouldn’t it still be okay to eat? It can’t have become contaminated within such a short time, right? Or could it have?

Today’s Wonder of the Day takes a closer look at that unique superstition we all know as the five-second rule. It holds that food dropped onto the floor is still safe to eat as long as it’s retrieved and consumed within five seconds of being dropped. But is there any truth to it? Is dropped food really safe to eat as long as you do so quickly?

Some of you may be asking why we’re even talking about this at all. The thought of eating something that has hit the floor is simply unacceptable to many people. The very idea that a stray piece of hair or dirt has attached itself to the dropped food makes it off-limits to many. You can always get another potato chip, right? But others will grab that chip quickly and stuff it into their mouths, often with an accompanying shout of “Five-second rule!”

Since this “rule” is so widespread, we thought it was worth taking a look. We wanted to know if it had any actual scientific merit … or if it’s just a potentially dangerous superstition . And we’re in good company, since scientists have actually spent some time studying this phenomenon .

Based upon the available scientific research, it appears that the five-second rule is just a myth . Foods dropped onto the floor can quickly become contaminated with germs within a matter of seconds. The longer food remains on the floor, the more germs it’s likely to attract.

The type of surface food falls upon does matter. Clean, dry floors are less likely to have germs than are moist surfaces or carpet. Where the floor is located matters, too. A high-traffic area, such as a hallway, will likely have more germs and dirt than other areas.

Are a few germs a big deal, though? They definitely can be. Bacteria and viruses can cause all sorts of illnesses. Some of these bad germs , such as E. coli , salmonella, and hepatitis, can lead to life-threatening sickness. Even those food-borne illnesses that aren’t life-threatening are still not fun to get.

So, if your food hits the floor, why not play it safe? Just pick it up and put it in the trash. This may be easier to do if the food is broccoli as opposed to chocolate, but your health is important. Don’t take a chance. Pitch it and get some more food. No potato chip is worth the risk of a food-borne illness!

Common Core , Next Generation Science Standards , and National Council for the Social Studies ."> Standards : NGSS.LS1.A, CCRA.L.3, CCRA.L.6, CCRA.R.1, CCRA.R.2, CCRA.R.4, CCRA.R.10, CCRA.SL.1

Wonder What's Next?

Tomorrow’s Wonder of the Day takes a closer look at some really needy creatures!

Hungry yet? Today's Wonder of the Day may have made you lose your appetite just a bit, but don't worry! It'll come back. In the meantime, why not check out one or more of the following delicious activities with a friend or family member:

• If you're worried about the five-second rule at home, why not take some precautionary steps? What are we talking about? Clean the floors! Believe us, your parents will thank you. Grab the vacuum cleaner and help your parents clean all the carpets in your house. You can also help them scrub wooden, tile, and other surfaces. Take the time to make sure all the floors in your house are sparkling and clean. As you clean, pay close attention to the dirt and grime that you uncover. Even the cleanest floors manage to attract dust and dirt that's not usually visible to the naked eye. When you're done with the vacuum cleaner, for example, help your parents clean out the vacuum bag and the filter. Can you believe the junk that was sucked up out of the carpets? Would you want any of that on your food? No way! Hopefully this little exercise will help you think twice the next time you drop that potato chip on the floor and think about eating it!
• Take some time to ponder the following question: why is there a five-second rule? How did it get started? Have you ever eaten food that has fallen on the floor? Under what circumstances would you eat food that you dropped? Would it matter on what kind of floor it fell upon? Would the type of food matter? Or is any food dropped simply destined for the trash can? Poll your friends and family members to see what their opinions are. You might be surprised by the range of responses you get. Where would you draw the line? Where would friends and family members draw the line? Many people might not think twice about eating a potato chip that had fallen off the edge of a plate onto a table. But what about a piece of fruit dropped onto the floor of the bathroom? Have fun exploring the edges of the five-second rule!
• How would you go about scientifically testing the five-second rule? Come up with a list of ideas that you think would work. When you're finished, watch the Mythbusters Five-Second Rule video to see what they did. Did you come up with similar ideas? How might you have done things differently? What would you change about their experiments?

Wonder Sources

• http://en.wikipedia.org/wiki/Five-second_rule (accessed 25 Oct. 2019)
• http://science.howstuffworks.com/science-vs-myth/everyday-myths/five-second-rule.htm (accessed 25 Oct. 2019)
• http://jezebel.com/5967257/sorry-floor-eaters-the-5+second-rule-is-definitely-a-myth (accessed 25 Oct. 2019)
• http://www.webmd.com/a-to-z-guides/features/5-second-rule-rules-sometimes- (accessed 25 Oct. 2019)

Did you get it?

Wonder contributors.

We’d like to thank:

Dee , Marty from AL, shanice , Taylor and Amanda from WI for contributing questions about today’s Wonder topic!

Keep WONDERing with us!

Wonder Words

• contaminated
• accompanying
• superstition

We're glad you liked it, leeland!

sommer and parker

yes it is really ture

That's a great way to think of it, sommer and parker! 

What do you mean you eat stuff off the floor that isn't food!!??

That's not a very safe thing to do, Big Jenny! We should always be mindful about what we put in our mouths.

well I don't agree with you food is food and live you life it doesn't matter what other people think of yuou PERIOd

Thanks for sharing your thoughts, tina.

congrats 4 making it a tradition!!!!!! ?????????????

We agree with you, Josh.

me epic chill

Sounds risky to us, Nick! 

Hrm. Interesting. Thanks for stopping by, Trent.

Hi Jaxom29! 

We think it depends where you are. If you're at home, it's one thing. If you're in public, there's a chance for more germs. 

Xander Knowles

Do you need the extra 4m 55s? I do.

this is fake lol

?  ?  You get a ? for that, Bruno.

That's fair, Shannon! 

Thanks, landyn! What did you learn from this Wonder?

Hi, Ella! Check out  Wonder 232: What Is an Old Wives' Tale?   for other superstitions you may have heard!

And now you know why, right??

Yeah, it turns out it is. ?

awsome job sooo creavite

Thanks, 76! Glad you enjoyed a Wonder that was a little outside of the box. Happy WONDERing!

hi i love this website

We're glad you're WONDERing with us, chylia!

Hi, Jaz! We're glad you liked this Wonder! Thanks for WONDERing with us! :)

I have I thought was true

A lot of people have probably thought this "rule" was true, too, Dj! We're glad you checked out this Wonder and learned more about the "Five-Second rule!" Thanks for sharing your thoughts!

Thank you for adding your comment, maanya! We're very glad you are WONDERing with us! :)

can you stop replying back @wonderopolis it gets annoying

well that's a little bit unnecessarily rude ?

Thanks for being a great Wonder Friend, Matteo! 

Sorry we annoyed you, Julie! We strive to respond to all comments from our Wonder Friends because we love chatting with everyone!

We're glad you liked this Wonder, Wonder Friend! We hope you learned more about the five second rule! :)

We're glad you liked this Wonder, too! Thanks for stopping by! :)

Hi, Kaylee! We hope you learned more about the five second rule! We think it's better safe than sorry and avoid eating food from the floor! :)

?????????????

oh yea i waited 2.9 seconds!

Thanks for sharing, joe!

the five second rule is not true

We agree, nehchal!

!!!!!!!!!!!!

i wait until 20 seconds!

Risk-taker.

Hi, Wonder Friend! We hope you learned more about the 5 second rule! Unfortunately, it's not true! We think it's better to be safe than sorry when food falls on the ground! :)

That's a good thing, Madison! We're sure you probably agree after reading this Wonder! :)

That's an interesting question, Nooblyn! We're not sure! That would be worth continuing to research! :)

Is it really true that there is no five second rule

Hi, Luke! Yes, that's right! We encourage you to read the Wonder to learn more! :)

Great, Boom! We're THRILLED you learned something new! That's always the goal when we're WONDERing! :)

Cringe level 1,000,000,000

We think lots of our Wonder Friends did too, Natalie! Thanks for WONDERing with us! :)

Thanks for sharing your opinion, garfield! We hope this Wonder helped you learn a little more about the five second rule! :)

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We agree, ariana! As this Wonder tells us, the five second rule is a myth! Better safe than sorry! :)

A fabulous five

you think that is just aww

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Wonderopolis

Hi, kale! Many people believe in the five second rule. However, based on the scientific evidence, it seems to be a myth and just a few germs do matter. Did you know that germs can actually good, too? Check out Wonder #484: Can Germs Be Good for You? . Happy WONDERing! :)

Questionable Dude

I agree with you Questionable Dude. Why come up with different second rules if they're useless!

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You're right, Questionable Dude! According to the WONDER, any amount of time on the floor, can cause germs to get on the food. We must be very careful when eating!! :)

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Hello, Sarah, Leala, and Peyton! We're glad that you found this article interesting. You may want to warn your friends the next time they try to eat something off of the floor. Keep WONDERing, Wonder Friends! :-)

We think it is safest not to eat off the floor at all, Raegan. What do you think? Thanks for WONDERing with us today! :-)

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Goku plus el

I am an anime fanatic and I already think twice because of anime

Hi, Wonder Friend! Anime is super cool! Are you a fan of Minecraft? Check out Wonder #1206: What Can You Mine with Minecraft? Have fun WONDERing! :)

We agree, Dylan! Eating off of the floor is gross! Now we know it's not a good thing to do. Thanks for WONDERing with us today, Wonder Friend! :-)

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For me it is not a myth.

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Hi Hannah, we're so glad you learned something new with us today! We are very happy to hear that you're going to share this Wonder with your friends, too! HOW AWESOME! :) Life-threatening diseases are not common, but they do happen to people all over the world. Perhaps you can ask your doctor about those diseases the next time you go in for a check up! We've got instructions for a :) right here: Colon : + closed parenthesis ) = :+) = :)

Hey Michelle, thanks for sharing that awesome information with us! It sounds like we have lots to Wonder about, including this great information your mom read. We Wonder if there have been multiple studies testing bacteria and how quickly it can infect food. We hope you'll continue to research this Wonder with your family! :)

Hey Michelle, great questions! We're so glad you shared your awesome connections with us today! The inventor of the five-second-rule is unknown, but we sure do know a lot of people who think it's real! It's important to avoid germs if you can, and throwing away food that's fallen in an unclean place (like the floor or on the sidewalk) is one easy way to do it. However, if your food is wrapped in plastic and protected, you can pick it up, dust it off, unwrap your food, and enjoy! :)

Vollyballguy

Hey Volleyballguy! Thanks for WONDERing with us! We're glad you're using your scientific imagination to test this Wonder, but we don't want you to get sick! Sometimes germs are more powerful than others... so it's best to pick up the food you dropped and toss it, just to be safe! :)

Great question, William! Some may say yes, some may say no. However, there are still germs that find their way to your food if you drop it. It's up to you to decide if you want to eat it! :)

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Thanks for sharing your opinion about our Wonder of the Day®, Madison! We're glad you're WONDERing about the germs all around us and how to stay healthy! :)

Patricia Herrera

Alright, we're so happy our Wonder Friends from Ms. Herrera's class are here today! Thanks for sharing your clean and healthy comment with us - we love learning about all the connections you have to this Wonder! The bottoms of our feet and shoes sure do get dirty... we wouldn't want to eat food that touched those surfaces, would we? :)

Mrs. Bahler's class

WOOHOO for WONDERing with Mrs. Bahler's class again! We think it's great that you are WONDERing about both side of the five-second rule argument. What great debaters you are, Wonder Friends! :)

Alright, we're so excited that our Wonder Friends from Mrs. Bahler's Class are here today! We think it's cool that you've been sharing your connections between this Wonder and family and friends who have tested the five-second rule. We are learning so much today with the help of awesome friends like you! We Wonder what percent of your classroom agrees with the five-second rule? :)

Thanks for sharing your comment, Ethan! We are glad you are WONDERing with us today! We hope you're using the five-second rule on super clean surfaces - we wouldn't want you to get sick! :)

Mrs. LaLonde's Class

Thanks for sharing what you learned and WONDERed with us today, Mrs. LaLonde's Class! Science is super cool and we're glad we learned about how quickly germs can spread. WOOHOO for staying healthy and full of cool information! :)

Hey Max! WOW, we hope you took that new-found cracker and sent it straight to the garbage can! Thanks for WONDERing with us today, friend. We think you're on to something... can't wait until tomorrow's Wonder! :)

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Thanks for sharing your thought about our Wonder today, TJ! We're glad you're doing things to stay healthy and clean! :)

london mrs.liles class

Hi London, thanks for WONDERing with us today! We've learned so much about science, and germs, and the food we eat! HOORAY for using our awesome brains! :)

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We're glad to hear from so many clean and healthy Wonder Friends today, Deven! We're happy that you don't use the five-second rule and you are germ-free! :)

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Thanks for comparing your home to your school, Kylee, we think that you have done a great job WONDERing with us today! Speaking of dogs and bones, we bet you'll like this Wonder: #1007-- Does Your Pet Have a Personality? https://www.wonderopolis.org/wonder/does-your-pet-have-a-personality/ :)

jacob/mrs.liles class

We love your enthusiasm, Jacob! We are happy to know that you will be a clean and healthy Wonder Friend! We are so glad you shared your love of trains with us, too! What's that... coming down the track? https://www.wonderopolis.org/wonder/what-is-the-fastest-train/ :)

Janiya ms liles class

What a great connection about today's Wonder, Janiya! Hospitals are very clean places in order to keep its patients healthy so they can get better. We are glad you've been WONDERing about the cleanest places around! We look forward to WONDERing with you tomorrow... what a great prediction you have! :)

chett- Mrs. Liles' Class

If your food falls somewhere nice and clean, we think you're in a good spot to eat it, too, Chett! However, like those Wonder Friends mentioned in the video, if food fell on the cafeteria floor, it must go in the garbage! :)

christopher mrsliles class

Thanks for sharing your comment about our Wonder today, Christopher! We are glad you're one healthy and germ-free Wonder Friend! We think you'll enjoy this flag Wonder in the meantime: #554-- Do All Pirate Ships Have Flags? https://www.wonderopolis.org/wonder/do-all-pirate-ships-have-flags/ :)

Jeremiah - Mrs. Liles' Class

We're so glad you've been WONDERing about the people all over the world who might use the five-second rule, Jeremiah! Nice work, Wonder Friend! We only like to use the five-second rule when our food is in a package or wrapped up! :)

Brandon mrs.liles

What great predictions, Brandon! We're glad you're WONDERing about the five-second rule with us today, you can share this Wonder with your brother! How WONDERful! :)

kaylen mrs.liles class

Hey there, Kaylen, we think you did a great job WONDERing with us today! We love your Wonder word example - we've got a state fair Wonder just for you: #944-- Have You Ever Been to a State Fair? https://www.wonderopolis.org/wonder/have-you-ever-been-to-a-state-fair/ :)

Erick - Mrs. Liles' Class

Thanks for WONDERing with us, Erick! We loved WONDERing about the science behind germs and our food! We are glad you aren't eating food that's fallen on the ground, Wonder Friend, we want you to stay healthy! :)

keith mrs.liles class

While we're not sure WHO came up with the five-second rule, there sure are a lot of folks who use it, Keith! We're glad that you're not taking part in it, we want you to be germ free! :) We think you're on the right track for tomorrow's Wonder! :)

Elizabeth mrs.liles class

Thanks for WONDERing with us today, Elizabeth! We are glad you're staying healthy and happy, Wonder Friend! We think you're on the right stripe... we mean... path with tomorrow's Wonder of the Day®! :)

YUM, we love candy (but just a little bit, we wouldn't want to hurt our teeth), Tairyn! Thanks for sharing your comment with us today - we are glad today's Wonder made you smile! Check out our sweet treat Wonder: #448-- How Did Candy Canes Get Their Shape? https://www.wonderopolis.org/wonder/how-did-candy-canes-get-their-shape/ :)

Danessa Mrs.lies class

We bet lots of babies put things in their mouths, just like you mentioned, Danessa! It's part of the teething process - they are curious and they like to chew on just about anything they can find! We have a lot of animal Wonders for you to enjoy, check out our category here: https://www.wonderopolis.org/wonders/?subject=animals :)

destiny - Mrs.liles

We are glad you're thinking of mice and other animals who eat off the floor, Destiny! We love your comment for today's Wonder! :) We hope you enjoy our stripe Wonder about zebras right now: #852-- Why Do Zebras Have Stripes? https://www.wonderopolis.org/wonder/why-do-zebras-have-stripes-2/ :)

Why does everyone think the next video is gonna be about zebras? I don't understand why.

Hi Alyssa, you can check out our "Wonder What's Next" section and share your prediction for tomorrow's Wonder of the Day®! :)

Hey Andrea, we're glad you're tossing food that has fallen on the floor. You're a healthy Wonder Friend! :) We think you're going to like tomorrow's Wonder... it has lots to do with rules! :)

jeremiahmrs.liles class

Hi Jeremiah, it sounds like you have seen the five-second rule in action! We think you did a WONDERful job using the Wonder word of the day in a sentence, too! Nice work! :)

Tam Mrs.Liles' class

Hi Tam, we're so glad you're here today! Thanks for sharing what you learned with us today - bacteria sure does travel quickly! We think you're mom has a super imagination - we like her term, Vitamin D, vitamin dust! :)

William Muprhy

WOW, what a great comment, William! You're right- germs are speedy and attach themselves to food in less than a second! :)

Thanks for sharing your trick, Jordan! We think we've all been guilty of using the five-second rule from time to time... but we're glad to Wonder with you today. We learned about keeping ourselves healthy, and a great way to avoid germs is to throw away any food that has touched the floor! :)

Thanks for sharing your comment, Kate M! We are glad you're thinking of ways to be healthy! :)

Nice work, Jason! :)

What a SUPER stripe Wonder guess, Amelia! Check out this Wonder in the meantime: #852-- Why Do Zebras Have Stripes? https://www.wonderopolis.org/wonder/why-do-zebras-have-stripes-2/ :)

aidan lyons

Great question and prediction, Aidan! A clean floor is a great place to drop food - you are most likely germ-free! However, as soon as people begin to walk on the floor, germs can find their way back! :)

What a great guess, Xavion! Check out this cool Wonder about the American flag in the meantime: #274-- Who Made the American Flag? https://www.wonderopolis.org/wonder/who-made-the-american-flag/ :)

Mikayla Coe

Hi there, Mikayla, thanks for WONDERing with us today! The five-second rule is a rule that's okay to break - we learned that it's better to throw away food that has fallen on the floor instead of quickly picking it up. Germs can still attach themselves to food as soon as it hits the floor. Glad we WONDERed about this today! :)

Hey Jack, sometimes our stomaches take over and our mind just doesn't think about the germs on the floor. If you drop a super tasty piece of cake, it's very sad, and sometimes, without thinking, you pick it up quickly and eat it! We're glad we WONDERed all about the germs that attach themselves to food that falls on the floor. We want to be happy and healthy Wonder Friends! :)

We are glad you shared your opinion, Sadie! Thanks for WONDERing with us today and telling us your thoughts about the five-second rule! :)

That's a great plan, Jasmine S! We think you're one healthy Wonder Friend! :)

korean thomas

Hey Korean, great question! Many of the germs on the floor the folks walking on the floor - the bottom of people's shoes are not very clean! However, a cabinet might not be as dirty as a floor, but there are still germs. What do you think, Korean? :)

Elijah Bentson

Hey there, Elijah! Thanks for sharing your comment with us today. We sure don't want you to get sick from the germs on the floor, but we love your honesty! :)

Sometimes our stomaches overpower our brains, Taquirria, and we think that if we pick the food up quickly, it won't matter! However, we're glad to learn about the truth today - food falling on the floor is not worth eating! :)

Byancah-LaN'aye Thomas

There can be if there is a 5 second rule right?

Great point, Gabe! Do you use the five-second rule? :)

Thanks for WONDERing with us today, Byancah! It seems that no matter how long food is on the ground it's still possible for germs to attach themselves to the food. We are going to follow the saying, "When in doubt, throw it out!" :)

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Question 1 of 3

According to the five-second rule, it’s still safe to eat food that has been dropped on the floor as long as you do what?

• a pick it up and eat it within five seconds of being dropped Correct!
• b turn around in a circle five times first Not Quite!
• c microwave the food for five seconds before eating it Not Quite!
• d let the food sit on the floor for five seconds before picking it up Not Quite!

Question 2 of 3

Food dropped on the floor can be dangerous to eat if it picks up what?

• a E. coli Not Quite!
• b salmonella Not Quite!
• c hepatitis Not Quite!
• d all of the above Correct!

Question 3 of 3

What should you do if your food falls to the floor?

• a Pick it up immediately, and eat it. Not Quite!
• b Pick it up after 5 seconds, and eat it. Not Quite!
• c Pick it up, and throw it in the trash. Correct!
• d Do nothing, and let the dog eat it. Not Quite!

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The truth behind the '5-second rule': When in doubt, throw it out, expert says

The burger patty that slides off the plate, the ice cream treat that plops on the picnic table, the hot dog that rolls off the grill -- conventional wisdom has it that you have five seconds to pick it up before it is contaminated.

Fact or folklore?

"A dropped item is immediately contaminated and can't really be sanitized," said Jorge Parada, MD, MPH, FACP, FIDSA, medical director of the Infection Prevention and Control Program at Loyola University Health System. "When it comes to folklore, the 'five-second rule' should be replaced with 'When in doubt, throw it out.' "

All items that come into contact with a surface pick up bacteria (and dirt!). How much bacteria and what kind of microbes it pick up depends on the type of object that is dropped and the surface it is dropped on, he said.

"If you rinse off a dropped hot dog, you will probably greatly reduce the amount of contamination, but there will still be some amount of unwanted and potentially nonbeneficial bacteria on that hot dog," said Parada, who admits to employing the five-second rule on occasion. "Maybe the dropped item only picks up 1,000 bacteria but typically the innoculum, or amount of bacteria that is needed for most people to actually get infected, is 10,000 bacteria. Well, then the odds are that no harm will occur. But what if you have a more sensitive system, or you pick up a bacteria with a lower infectious dose? Then you are rolling the dice with your health or that of your loved one."

And using your own mouth to "clean off" a dropped baby pacifier?

"That is double dipping -- you are exposing yourself to bacteria and you are adding your own bacteria to what first contaminated the dropped item. No one is spared anything with this move," Parada said.

Parada likened this scenario to being burned, with temperature and time being analogous to type and amount of bacteria.

"The hotter the surface, the easier and worse you will be burned -- like the more virulent, or harmful, the bacteria, the easier and sicker you may get. One only has to touch a white-hot surface momentarily to get burned and sometimes it doesn't take a lot of bad bugs for you to get sick. On the other hand, if hold your hand to a less hot surface but do so for a longer period, the more you will be injured, too."

Parada said there are degrees of risk of contamination.

"So a potato chip dropped for a second on a rather clean table will both have little time to be contaminated and is likely to only pick up a miniscule amount of microbes -- definitely a low risk," he said. On the other hand, food that lands on a potentially more contaminated spot -- such as the floor -- and stays there for a minute is going to pick up more bacteria and pose a greater risk.

"In the same time period, a rock candy is less likely to pick up contamination than a slice of cheese. As an extreme example, whether it's a rock candy or a slice of cheese, I don't think anyone would invoke the five-second rule if it fell in the toilet," said Parada, a professor at Loyola's Stritch School of Medicine. "At the end of the day, this is a polite social fiction we employee to allow us to eat lightly contaminated foods," Parada said.

And that old saw about building up a healthy immune system through exposure?

"There actually is certain research that supports the importance of being exposed to bacteria at critical times in a child's development," Parada said. "But I believe this development applies to exposures of everyday living. I do not advocate deliberately exposing ourselves to known contaminants. That would probably be a misplaced approach to building up our defenses. If you want to be proactive in building up your defenses, eat right, exercise and get adequate sleep -- and remember to get your vaccines."

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Designing your own experiment to debunk the ‘five-second rule’

We’ve all been there. You’re excited to take a bite out of your lunch, but then it drops on the floor. You quickly pick it up, but — is it safe to eat?

In Eureka!Lab’s second DIY Science video, science education writer and resident scientist Bethany Brookshire puts the  five-second rule  to the test. Bethany finds that bacteria don’t really wait for the count of five. If food has fallen, it probably has microbes all over it.

The video and accompanying blog posts walk you through how to design an experiment, grow your own microbes, and analyze results to test whether food left on the floor for only five seconds picks up fewer microbes than food left longer.

View the video below:

Read the blog posts:

• The five-second rule: Designing an experiment
• The five-second rule: Growing germs for science
• The five-second rule: Myth busted?
• The five second rule: Microbes can’t count

Happy experimenting! And hang onto your food.

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Can I still eat it? Using problem-based learning to test the 5-second rule and promote scientific literacy

Elizabeth a hussa.

1701 N. State Street, Jackson, MS 39210. Millsaps College

Associated Data

Defining appropriate student learning outcomes for general education science courses is a daunting task. We must ask ourselves how to best prepare our students to understand the role of science in their lives and in society at large. In the era of social media and armchair experts, life-changing scientific advancements such as vaccination are being dismissed or actively resisted, emphasizing the critical need to teach science literacy skills. One active classroom method known as problem-based learning promotes self-motivated learning and synthesis skills that, when applied in a science-literacy context, can provide students with the ability to generate informed opinions on new scientific advances throughout their lifetime. This piece describes one such problem-based course, designed to tackle the scientific basis (or lack thereof) of the 5-second rule for eating food dropped on the floor. In this course, first year students experimentally engage this issue, while also applying their developing skill set to sort out scientific controversies such as vaccine safety and genetically modified foods.

This work provides both a theoretical and actionable blueprint for the development of a problem-based microbiology course for non-major undergraduate students to promote science literacy.

PROBLEM-BASED LEARNING

In problem-based learning (PBL) pedagogy, student groups engage with an open-ended question or related set of questions as a means to encounter course content while developing discipline-specific problem-solving tools (Barrows and Tamblyn 1980 ). Originally developed as a means to connect information to application in medical education, this method is one of the ways we can teach science as science is done. In fact, simply engaging students in hypothesis-driven research is a PBL methodology. The goals of PBL include the development of self-directed and motivated learning skills, usually with an emphasis on collaboration (Barrows and Kelson 1995 ). This shift toward skill development puts PBL well in line with a modern approach to science education (AAAS 2011 ), however there is lingering concern about the potential sacrifice of course content, which can lead to reduced scoring on standardized tests (Hmelo-Silver 2004 ). Current trends in undergraduate biology education resolve these concerns by placing PBL classes, including undergraduate research projects, near the beginning of the curriculum in an effort to ‘jump start’ student engagement and with the hope that students will develop the metacognitive skills necessary to succeed in their approach to content-driven courses that they encounter later in the curriculum (Russell, Hancock and McCullough 2007 ).

While PBL is quickly becoming an important part of a science curriculum, it could also be an important approach to teaching non-majors science courses. These general education courses are often our one opportunity to reach students who will go out into the world and be faced with making tough decisions about scientific progress from the doctor's office to the voting booth. This would support the call to emphasize science literacy skills, or the ability to acquire, critically evaluate, and apply scientific knowledge to new problems in these general education courses (Wright 2005 ). While the occasional ‘traditional’ general biology student may think about aerobic versus anaerobic respiration while gasping for air and racing to get their child to the pediatrician's office on time, one might argue that it is more impactful that they can make an informed decision as to the safety of vaccinating their child once they get there. PBL courses can help these students develop the ability to critically evaluate sources, understand data and recognize the importance of statistics when researching these important issues.

As microbiologists, we are in a unique position to offer problem-based courses to students at all levels, regardless of major because classic microbiological methods and questions are (1) accessible, (2) relevant to everyday life and (3) inexpensive. As instructors, we can invest a small amount of time training students how to inoculate petri plates and use proper sterile technique, preparing them for an entire semester of inquiry. We can subsequently spend more of our contact hours with students focused on hypothesis development and testing, as well as data analysis. Innovative microbiology-based pedagogies are becoming more popular (Strobel and Strobel 2007 ; Jordan 2014 ; Fahnert 2017 ), and are making their way into general education curricula as a means to reach a diverse population of students. Bard College has a mandatory, microbiology-based ‘Citizen Science’ course that challenges first year students to engage with primary literature and perform wet lab experimentation centered around a current scientific issue (Savage and Jude 2014 ). At Millsaps College, I have offered a similar first year course titled ‘The 5-second Rule: Can I Still Eat it?’ since the fall of 2015. The course directs students to experimentally examine the popular folklore about the safety of eating dropped food retrieved before 5 seconds, while at the same time asking them to link what they’ve learned to ‘bigger picture’ scientific controversies. The course is taught in three phases, which are outlined below.

Phase I: Setting the stage

Teaching a PBL course can feel very foreign to those of us used to traditional lecture-based teaching methods. The instructor in a PBL course must put the majority of their effort into the setup of the course in order to facilitate student-driven learning during course execution. This typically involves providing a framework to which problem solving can be applied (Schmidt et al. 2007 ). In science, of course, this framework is the scientific method. In the 5-second rule, we spend the first 2-3 weeks setting the stage, wherein student groups engage with hypothetical scenarios to facilitate discussion of the scientific method. For example, students are asked to develop an experiment to test the hypothesis that college students like both oatmeal and chocolate chip cookies, but prefer chocolate chip. This results in a discussion of the elements of good experimental design so that we can layer on, or ‘scaffold’ scientific knowledge and techniques later. Another scenario presents students with two data sets representing differences in student height by sex. Each data set has the exact same sample size and average height, but different distributions of data. This prompts discussion of data analysis, including basic statistics (Student's t- test). These exercises provide a low stakes way for students to build confidence toward eventual application of the scientific method.

Phase II: Experimental investigation

The second phase of the 5-second rule allows students to apply their knowledge of the scientific method to experimentation by first dividing the 5-second rule into single-variable experimental questions. Typically, students will choose to investigate (1) the presence of microbes on various surfaces onto which food might be dropped, (2) the effect of food type on microbial transfer and (3) the effect of time of surface exposure on microbial transfer. For each experiment, the student group will first find relevant information from reliable sources to develop a hypothesis. Next, they will be given a list of materials they will be able to access for their experiment. This provides more scaffolding for students to feel supported and give them subtle direction without handing them a protocol. Groups then develop experimental methods using a handout that asks them to identify controls and predict results based on their hypothesis. After meeting with the instructor and receiving approval to move forward, student groups conduct experiments independently and meet with an instructor or teaching assistant to ensure proper data interpretation. An example set of assignments for a single experiment is included in the supplementary materials . Finally, the group prepares a standard laboratory report with a collaboratively-written abstract and individually-written introduction, methods, results and conclusion sections. Students rotate written sections throughout the semester so they can isolate and focus on one section at a time. Finally, students within a group engage in peer review of their collective work prior to submission. The last experiment of the semester involves conducting a multi-variable experiment to test the 5-second rule, with individually-written lab reports.

Phase III: Metacognition and application

One of the goals of PBL courses in general is to provide students with lifelong learning skills, as well as the ability to understand and apply these skills in other courses, or even in everyday life. Otherwise known as metacognition, the ability to ‘think about thinking’ is useful, especially in a student's early college career, to develop productive study habits (Downing et al. 2009 ). With this in mind, the third component of the 5-second rule course is actually distributed throughout the semester as a series of ‘hot topics in science’ discussions. Here, students investigate and discuss various controversies using a scientific basis for understanding. For example, one exercise may have students use a standard internet search engine to investigate the relative safety of genetically modified organisms. Students are instructed to categorize the search results as reliable or unreliable based on their knowledge of appropriate sources for science communication, and the class subsequently compares the relative abundance of reliable versus unreliable sources on the internet. It is critical that students participate in and reflect on a variety of problems so as to emphasize the universal nature of problem solving practices.

Engaging with both scientific experimentation and literature via problem-based learning provides a depth of experience that benefits students as lifelong learners. After course completion, 90% of 5-second rule students indicated that ‘taking this class has made me more likely to understand an article describing a scientific discovery’ ( P < 0.0001). The relatability and experimental tractability of microbiological problems such as the 5-second rule places our field at the forefront of these important pedagogical innovations.

Supplementary Material

Supplementary data.

This work was supported by the Mississippi IDeA Networks of Biomedical Research Ethics (INBRE), funded by an Institutional Development Award (IDeA) from the National Institute of General Medical Sciences of the National Institutes of Health [grant number P20GM103476].

Conflict of interest . None declared.

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Science Fair Projects

Free Science Fair Projects for school students

5-second rule science fair project

March 6, 2022 by ScienceProjects

In this 5-second rule experiment, we will learn about the 5-second rule science fair project. Find out if cleaning up dropped food in less than five seconds prevents germs from being transferred from the soil.

Material required

● Foods that will be evaluated (e.g., wet items like lunch meat and dry items like a jelly bean). Each item tested will require six copies. ● Swabs that are sterile ● Gloves that are sterile ● Timer ● Prepared nutrient agar in sterile plates ● Keep a notebook to keep track of your progress.

5-second rule Procedure

1. Using nourishing agar, make 12 sterile plates. 2. Wear a pair of sterile gloves (do not touch any non-living surface while wearing gloves). 3. Now, need to select two types of ground surfaces. 4. Discard the first test object (a piece of lunch meat, for example) onto the first sort of ground. 5. Kindly Set the timer 6. Remove the object from the ground after five seconds. 7. Using a sterile swab, clean the object (do not touch anything else with the swab). 8. The top of the petri dish should be removed. Keep your hand away from any non-living surfaces when holding the top of the bowl. 9. Slowly move the swab back and forth on the agar plate’s surface in a zigzag manner. No area of the agar should be touched twice. 10. Return to the Petri dish’s top and label it. 11. Remove your gloves and replace them. 12. Replace the first item in the test (for example, a new piece of lunch meat). 13. Repeat the test twice more with a new object each time (for example, two different jelly beans). 14. Change the soil types and test each thing twice. 15. Items that haven’t been tossed on the ground should be swabbed. For each item tested, make two “control” agar plates. 16. Maintain a temperature of 37°C for Petri dishes. At room temperature, bacteria take longer to proliferate. Ensure that all of the Petri dishes are stored together. 17. Time intervals of 24 hours, 36 hours, 48 hours, 60 hours, and 72 hours are used to photograph plates. 18. On each plate, count the number of bacterial colonies at each location.

The evidence in front of me demonstrated that the results of dry food are not equivalent to those of wet food. This knowledge can assist everyone in gaining a better understanding of germs and how they might harm us.

It may even assist us in becoming ill. We have a higher chance of avoiding becoming sick if we don’t pick up food off the ground.

The goal of this study is to see if the 5-second rule holds true for dry food on the floor.

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