Overview

Lesson Procedure

70-75 minutes of class time across 5 phases.

1. Warm-Up10 minutes
2. Direct Instruction20 minutes
3. Guided Practice15 minutes
4. Independent Practice20 minutes
5. Closure5-10 minutes

1. Warm-Up10 minutes

   Warm-Up Prompt

   "You drop a cracker on the kitchen floor and pick it up two seconds later. Would you eat it? Write your answer and one reason. Then write one piece of evidence that could change your mind."

   Give students three minutes, then take a quick hand count for "eat it" and "throw it out." Write two or three reasons from each side on the board. Point out that most reasons are opinions or personal stories. Ask what kind of evidence would settle the question, and steer students toward measurement: someone would have to put bacteria on a floor, drop food on it and count what moves. Tell students that scientists have done exactly that, and that today they will write an argument: a text that states a claim and proves it with reasons and evidence, while answering the other side.

2. Direct Instruction20 minutes

   Define the parts of an argument with Diagram 1. A claim is the writer's position on a question that people can disagree about. A reason says why the claim is true, and evidence is the data or facts that prove the reason. An opposing claim (also called a counterclaim) is a position against the writer's claim; an alternate claim is a different answer to the same question. A credible source is one a reader has good reason to trust. In science, data are measurements, such as a percentage or a number of seconds. Work through the five examples below, then read the model argument aloud.

   • Stating a claim

     Vague draft claim: Germs on food are a big deal. It names a topic but takes no position that a reader could agree or disagree with.

     Result: Revision: Bacteria can reach dropped food in less than a second, so picking food up quickly does not make it safe to eat. (The claim takes a position and hints at the reason that will follow.)

   • Acknowledging and answering an opposing claim

     Opposing claim from Source D: germs need a few seconds to climb onto food. A writer who ignores it leaves the reader's doubt unanswered.

     Result: Revision: Some people believe that germs need a few seconds to climb onto food. Laboratory measurements do not support that belief: in the Rutgers study, some bacteria reached the food in less than one second (Source A).

   • Evidence plus reasoning

     Evidence alone: Watermelon picked up up to 97 percent of the bacteria. The number is accurate, but the reader is not told what it proves.

     Result: Revision: Watermelon picked up as much as about 97 percent of the bacteria on a surface, while gummy candy picked up about 62 percent at most (Source A). Because watermelon is wet and the candy is dry, moisture seems to help bacteria move, so the same five seconds can be riskier for some foods than for others.

   • Words that create cohesion

     Two sentences with no link: Longer contact moved more bacteria. Some bacteria moved in less than one second.

     Result: Revision: Although longer contact moved more bacteria, some bacteria moved in less than one second. ("Although" tells the reader that the second idea limits the first.)

   • Formal style

     Informal draft: The Clemson guys found out Salmonella hangs around on floors for like a month!!

     Result: Revision: Researchers at Clemson University found that Salmonella survived on dry surfaces for up to four weeks (Source B). (The scientists and the bacterium are named exactly, the number comes from the source, and slang and exclamation marks are gone.)

   On a second reading, students number the paragraphs, box the claim, write R1 and R2 in the margin next to each reason, underline each piece of evidence and circle every source label. Ask: in which paragraph does the writer turn to the other side, and what word marks the turn back to the writer's own claim?

   1Almost everyone has heard the five-second rule: food dropped on the floor is safe to eat if it is picked up within five seconds. Some people treat the rule as a joke, while others believe that germs really do need a few seconds to reach food. To find out, food scientists have dropped food onto surfaces covered with bacteria and measured what moved. Their results show that the five-second rule should not be used to decide whether dropped food is safe to eat, because bacteria can reach food in less than one second and because the kind of food and floor matter as much as the time.

   2The first reason is that bacteria do not wait. In a 2016 study at Rutgers University, Robyn Miranda and Donald Schaffner dropped watermelon, bread, buttered bread and gummy candy onto surfaces covered with bacteria. Some bacteria moved onto the food in less than one second, the shortest time they tested (Source A). A 2007 study at Clemson University found the same pattern with Salmonella, a bacterium that causes food poisoning: after only 5 seconds on a tile, bologna had picked up more than 99 percent of the bacteria on the tile (Source B). In other words, five seconds is more than enough time for bacteria to reach food.

   3The second reason is that time is only one of several factors. In the Rutgers study, watermelon, the wettest of the four foods, picked up the most bacteria, and gummy candy picked up the least (Source A). The floor mattered too: carpet passed fewer bacteria to food than tile did in both studies (Sources A and B). Because a juicy fruit on a tile floor and a dry candy on a carpet pick up such different amounts, a rule that counts only seconds cannot tell anyone which dropped food is safe.

   4Some evidence seems to support the rule. In 2014, a team at Aston University in England reported that food left on the floor longer picked up more bacteria, and that time was "a significant factor" (Source C). The Rutgers team also found that longer contact moved more bacteria (Source A). However, picking up more bacteria later is not the same as picking up none at first. The Aston results were announced in a press release, and the press release does not say that other scientists checked the work, while Sources A and B were published in scientific journals. Even the leader of the Aston team, Professor Anthony Hilton, warned that eating dropped food "still carries an infection risk" (Source C).

   5The evidence leads to one conclusion: a dropped snack can pick up bacteria the moment it lands. Picking food up quickly may mean fewer bacteria, but it does not mean no bacteria, and whether those bacteria can make someone sick depends on germs that no one can see. For that reason, the number of seconds should not decide whether dropped food is eaten.

3. Guided Practice15 minutes

   Pairs read the four sources the model argument draws on. Sources A-C summarize real studies; the summaries were written for this page, and the facts and quoted words come from the published study or press release. Source D is an invented blog post. As they read, pairs fill in the chart below for each source. They will use the chart again in Activity 2 and in the homework.

   Source chart (students fill in the last two columns)

   Source	Who wrote it and where it appeared	What it tested or claims	Data it gives (with numbers)
   A	Rutgers University scientists, science journal, 2016
   B	Clemson University scientists, science journal, 2007
   C	Aston University, press release, 2014
   D	An invented food blogger, blog post

   1Who and where: Robyn Miranda and Donald Schaffner, food scientists at Rutgers University in New Jersey, published this study in 2016 in the journal Applied and Environmental Microbiology. Before an article appears in this journal, other scientists check its methods and results.

   2What they did: The researchers spread a measured amount of a bacterium called Enterobacter aerogenes on four surfaces: stainless steel, ceramic tile, wood and carpet. They let the surfaces dry for 5 hours. Then they dropped four foods onto them from a height of 12.5 centimeters: watermelon, plain bread, bread with butter and gummy candy. Each food stayed on the surface for less than 1 second, 5 seconds, 30 seconds or 300 seconds, and then the researchers measured how many bacteria had moved onto it.

   3What they found: Longer contact moved more bacteria, but the type of food and the type of surface mattered as much or more. Watermelon picked up the most bacteria, from about 0.2 percent to 97 percent of the bacteria on the surface, depending on the surface and the time. Gummy candy picked up the least, from about 0.1 percent to 62 percent. Carpet passed fewer bacteria to food than tile or stainless steel did.

   4Their conclusion, in their own words: "Some transfer takes place 'instantaneously,' at times of <1 s, disproving the five-second rule."

   1Who and where: Paul Dawson and four colleagues at Clemson University in South Carolina published this study in 2007 in the Journal of Applied Microbiology. Before an article appears in this journal, other scientists check its methods and results.

   2What they did: The team put Salmonella Typhimurium, a type of bacteria that can cause food poisoning, on tile, wood and carpet. They then laid bologna and bread on the surfaces, after the bacteria had been on the surfaces for 2, 4, 8 or 24 hours. They also measured how long the bacteria could stay alive on a dry surface.

   3What they found: Salmonella survived for up to four weeks on dry surfaces, in numbers large enough to spread to food. More than 99 percent of the bacteria on the tile moved to the bologna after 5 seconds of contact. Carpet passed very few bacteria to the bologna, less than 0.5 percent, while wood and tile passed from 5 to 68 percent.

   4Their conclusion: the bacteria "can be transferred to the foods tested almost immediately on contact."

   1Who and where: On 10 March 2014, Aston University in Birmingham, England, announced the results of a study in a press release, a news announcement that an organization writes about its own work. The study was carried out by final-year biology students led by Anthony Hilton, a professor of microbiology. The press release does not say that other scientists checked the work before it was announced.

   2What they did: The team tested how two kinds of bacteria, E. coli and Staphylococcus aureus, moved from carpet, laminate and tile floors to toast, pasta, a cookie and a sticky candy. The foods stayed on the floor for 3 to 30 seconds.

   3What they found: Time was "a significant factor": food left on the floor longer picked up more bacteria. Bacteria were least likely to move from carpet, and most likely to move from laminate or tile to moist foods left for more than 5 seconds. The team also surveyed people and reported that 87 percent said they would eat food dropped on the floor, or had already done so.

   4What the lead scientist said: "Consuming food dropped on the floor still carries an infection risk as it very much depends on which bacteria are present on the floor at the time."

   1I have followed the five-second rule my whole life, and I have never gotten sick from a dropped snack. Neither has anyone in my family. Floors in most homes are cleaner than people think, and germs need a few seconds to climb onto food, so if you are fast, you are fine.

   2Scientists love to scare people about germs, but common sense says a quick pickup is safe. That is why I designed the Snack Talk Floor-Safe Bowl, which has a rubber base so it never tips over. Order yours today and stop wasting food!

   3Posted by Casey R., food blogger

4. Independent Practice20 minutes

   Students read the weak draft below, which a student wrote after hearing about the five-second rule but before reading any sources. They number its seven sentences and label each one: claim, reason, evidence, opposing claim, conclusion or none. Then they list its problems under four headings: claim and opposing claim, data and sources, formal style, and conclusion. They do not rewrite it yet; that happens in Activity 3.

   The five second rule is totally fake and honestly anyone who believes it is kind of gross. Germs are everywhere so obviously they get on your food. Scientists did a study and found out germs get on food. My friend dropped a cookie at lunch and ate it and got a stomachache the next day, so that proves it. Some people say the rule is real but they are just wrong. Also carpets are super dirty so food on a carpet gets the most germs. In conclusion, germs are bad and everyone should wash their hands more.

   Next, each student starts the plan for the homework argument, which asks a new question: Is carpet a safer place than tile to drop food? On a planning sheet they write a working claim, two reasons, one piece of data for each reason with its source label, and the strongest opposing claim they can think of. Collect the plans or check them at the door.

5. Closure5-10 minutes

   Exit ticket: (1) Write one sentence that states an opposing claim about the five-second rule fairly. (2) Write the sentence that answers it, beginning with a transition. (3) Name one question you ask to decide whether a source is credible.

   Teacher notes: Source D, its writer Casey R., the Snack Talk blog and the Floor-Safe Bowl are invented for practice, and so is the student who wrote the weak draft; say so when you hand them out. The summaries of Sources A-C were written for this page, so students should cite them as "Source A" and so on, not as the original articles. This lesson includes no lab. Do not culture bacteria from floors or food for it: growing unknown bacteria needs plates that are sealed and never reopened, and disposal by the teacher under your school's biosafety rules. Do not use real food in the activities, and never let students eat food that has touched the floor, desks or lab benches; check for food allergies before any food appears in class.

Differentiation Strategies

Assessment Guidance

1. Question 1 of 20 · Multiple Choice

   Which writing task asks for an argument focused on science content?

   AExplain the steps that food scientists follow to count the bacteria on a sample. BArgue whether the five-second rule is a safe guide, using data from studies. CTell the story of a time you dropped your lunch on the cafeteria floor. DArgue whether pizza or tacos make the better school lunch on Fridays.

2. Question 2 of 20 · Multiple Choice

   Which sentence in paragraph 1 of the model argument (T5) states the writer's claim?

   A"Almost everyone has heard the five-second rule: food dropped on the floor is safe to eat if it is picked up within five seconds." B"Some people treat the rule as a joke, while others believe that germs really do need a few seconds to reach food." C"To find out, food scientists have dropped food onto surfaces covered with bacteria and measured what moved." D"Their results show that the five-second rule should not be used to decide whether dropped food is safe to eat ..."

3. Question 3 of 20 · Multiple Choice

   Which sentence is an arguable claim that a science argument could prove with data?

   ABacteria are living things that are far too small to see without a microscope. BDoes the five-second rule really work for every kind of food, or only for some? CWet foods pick up more bacteria from a floor than dry foods, so they are riskier. DI would never eat food off the floor, because the whole idea is simply gross.

4. Question 4 of 20 · Multiple Choice

   Which sentence from paragraph 4 of the model argument (T5) first turns to the opposing claim?

   A"Some evidence seems to support the rule." B"However, picking up more bacteria later is not the same as picking up none at first." C"Even the leader of the Aston team, Professor Anthony Hilton, warned that eating dropped food 'still carries an infection risk.'" D"The Rutgers team also found that longer contact moved more bacteria (Source A)."

5. Question 5 of 20 · Multiple Choice

   How does the model argument (T5) distinguish its claim from the Aston finding that time is "a significant factor"?

   AIt argues that the Aston team measured the bacteria wrongly and so got the wrong results. BIt agrees that time matters, but points out that some bacteria reach food almost at once. CIt says the Aston team tested other foods, so its results do not count in the argument. DIt explains that the Aston team did not test carpet or tile floors in its study at all.

6. Question 6 of 20 · Multiple Choice

   The model argument (T5) gives both reasons in paragraphs 2 and 3 and answers the opposing claim in paragraph 4. Why is this order logical?

   AReaders see the evidence first, so the response to the other side can build on it. BAn opposing claim must always come last in an argument, just before the conclusion. CThe opposing claim is the weakest part, so the writer places it where readers skip it. DThe writer ran out of reasons and needed another paragraph to reach a word count.

7. Question 7 of 20 · Multiple Choice

   Which piece of evidence best supports the model argument's first reason, that "bacteria do not wait"?

   ASalmonella survived for up to four weeks on dry surfaces (Source B). B87 percent of the people surveyed would eat food from the floor (Source C). CSome bacteria moved onto the food in less than 1 second (Source A). DCarpet passed fewer bacteria to the food than tile did (Source A).

8. Question 8 of 20 · Multiple Choice

   Which sentence reports Source C (T3) accurately?

   AThe Aston team found that time on the floor made no difference at all. BThe Aston team found that carpet passed the most bacteria to the food. CThe Aston team tested foods left on the floor for 3 to 30 seconds. DThe Aston team published its results in a science journal in 2016.

9. Question 9 of 20 · Multiple Choice

   Which is the strongest reason to doubt Source D (T4)?

   AIt is shorter than the other three sources in the packet. BIt disagrees with the studies, so it cannot possibly be right. CIt gives no data, and its writer is selling a product. DIt was posted online, and nothing online can be trusted.

10. Question 10 of 20 · Multiple Choice

    Why does the model argument (T5) point out that Sources A and B were published in scientific journals?

    ATo show that journals publish only studies that disagree with popular rules BTo show that both studies were written for readers who are new to science CTo show that Rutgers and Clemson are older than Aston University in England DTo show that other scientists checked them, unlike the Aston press release

11. Question 11 of 20 · Multiple Choice

    Choose the transition that best shows the relationship between these sentences from Source B (T2): Carpet passed less than 0.5 percent of the bacteria to the bologna. ____, wood and tile passed from 5 to 68 percent.

    AFor example BAs a result CIn contrast DSimilarly

12. Question 12 of 20 · Multiple Choice

    In paragraph 4 of the model argument (T5), the sentence that begins with "However" links which two parts of the argument?

    AThe opposing evidence and the writer's response to it BTwo pieces of evidence that support the first reason CThe introduction and the writer's first main reason DThe writer's claim and the final concluding section

13. Question 13 of 20 · Multiple Choice

    Which revision of the weak draft's (T6) sentence Germs are everywhere so obviously they get on your food. keeps a formal style?

    AGerms are literally everywhere, so obviously they end up on your food no matter what. BYou should know that germs are all over the place, and they will totally get on food. CGerms are everywhere!!! That is why they get on food, which is seriously disgusting. DBacteria live on many household surfaces, and they can move onto food that touches them.

14. Question 14 of 20 · Multiple Choice

    Which concluding statement best follows from and supports the model argument (T5)?

    AIn conclusion, bacteria are fascinating, and scientists still have much to learn about them. BIn conclusion, carpet is the best floor, so families should replace every tile floor at home. CIn conclusion, the five-second rule is fine for most foods as long as people move quickly. DBecause bacteria can reach food at once, a quick pickup does not make dropped food safe.

15. Question 15 of 20 · Short Answer

    The weak draft (T6) begins: "The five second rule is totally fake and honestly anyone who believes it is kind of gross." Rewrite it as a formal introduction of two sentences that states a claim and acknowledges an opposing claim.

    Show model answer

16. Question 16 of 20 · Short Answer

    The weak draft (T6) says, "Scientists did a study and found out germs get on food." Rewrite the sentence so that it names a credible source and gives accurate data from it. Cite the source.

    Show model answer

17. Question 17 of 20 · Short Answer

    The weak draft (T6) says, "My friend dropped a cookie at lunch and ate it and got a stomachache the next day, so that proves it." In two or three sentences, explain why this story does not prove the writer's claim, and name a better kind of evidence.

    Show model answer

18. Question 18 of 20 · Short Answer

    The weak draft (T6) says, "Some people say the rule is real but they are just wrong." Rewrite this in two or three sentences that state the opposing claim fairly, give the evidence for it, and then distinguish the writer's claim from it, using a transition.

    Show model answer

19. Question 19 of 20 · Short Answer

    Put these four sentences in a logical order for one paragraph of an argument, and name the job of each one (reason, evidence, explanation or link back to the claim). Then name the transition that links the paragraph back to the claim.
    (1) For this reason, a floor that looks clean is not proof that dropped food is safe.
    (2) Bacteria can stay alive on a floor long after anyone can see a spill.
    (3) In the Clemson study, Salmonella survived on dry surfaces for up to four weeks (Source B).
    (4) This finding means that bacteria from a spill can still reach food weeks later.

    Show model answer

20. Question 20 of 20 · Short Answer

    The weak draft (T6) ends: "In conclusion, germs are bad and everyone should wash their hands more." Rewrite the conclusion in two formal sentences so that it follows from and supports an argument against the five-second rule.

    Show model answer

These standards connect to WHST.6-8.1: prerequisites to review first, parallel standards at the same level, and next steps that build on it.

Standard text: Common Core State Standards for English Language Arts & Literacy. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.