1. Lead a class discussion to have students share ideas about how germs spread and brainstorm how germs commonly enter human bodies.

• Connect to students’ previous experiences and learning from the Sick Days and Germs All around Us activities by asking:
• When you got sick from a germ, where do you think that germ came from? (Students’ responses may include: Items in my environment—door handle, sink faucet, etc., other people, or the air.)
• It may be helpful to point to the class Question Quadrant chart that helps to anchor students’ learning and ideas in this unit.
• Accept all student ideas, in the interest of building on their initial understanding.
• Highlight that the Germs All around Us activity focused on environmental factors and this activity will focus on how germs spread between people.
• Lead a class brainstorm to gather students’ ideas about how and where germs enter our bodies. Help students make connections between their responses to the opening question, as well as concepts from the Germs All around Us activity, such as:
• Ideas from the book Tiny: The Invisible World of Microbes (7:25) that germs can get into bodies through our mouths, cuts, or sometimes even insect bites.
• Accept all student ideas, emphasizing that for viruses such as the common cold, influenza, and the coronavirus, the nose and mouth are the main pathways for entering our bodies.
• Build on this idea to elicit from students how the nose and mouth are also key pathways for viruses to leave our bodies, through coughs and sneezes. 

2. Lead a class demonstration to simulate how sneezing helps germs travel between people.

• Building on students’ ideas from the previous step, explain that now they will demonstrate one important way that germs travel if we don’t cover our coughs and sneezes.
• Show a spray bottle filled with water and food coloring, then prompt students’ ideas about the demonstration by asking:
• How will this spray bottle model what happens during a sneeze? (The spray bottle represents a person’s nose and mouth, and the water represents germ-filled droplets that get forced out in a sneeze.)
• Before spraying (see Setup):
• Put down white butcher paper or another light-colored surface, so students can see how far the water droplets travel.
• Prompt students to predict how far the droplets will travel. Students can mark or add tape to show their predictions. 
• Simulate a sneeze with the spray bottle, repeating a few different times.
• Have a volunteer help measure the maximum length the droplets travel, using a meter stick, yard stick, measuring tape, or the previously-noted increments that you added to the paper or surface (see Setup). Record the data in a class chart.
• Invite students to see how close they were in their predictions.
• Then challenge students to determine how to make the sneeze droplets travel farther, and, conversely, brainstorm ways to keep droplets from traveling as a way to reduce the spread of germs.
• Determine as a class which two or three ways to test, and repeat the predictions, simulation, and measurements.
• Record the data in the class chart and have students create a line plot to represent the findings.
• Direct students to mark off the horizontal scale of the line plot in the unit fractions that are relevant to fourth grade math standards (see Standards). If working with third grade math standards, see Modifications.
• Lead a class discussion to debrief the simulations, with students using their line plots to support their understanding. Emphasize that droplets likely went a lot further than students predicted.
• Support data literacy and help students make connections between the simulation and real sneezes by describing the experiment and showing images from the article, See how a sneeze can launch germs much farther than 6 feet. Point out the finding in the article that “a fine mist of mucus and saliva can burst from a person’s mouth at nearly 160 kilometers per hour (100 miles per hour) and travel as far as 9 meters (27 feet).”
• Reflect on how measures such as covering the spray bottle helped to keep the droplets from traveling as far, and how we replicate this in real life by wearing masks or other preventative measures, to segue to the next step.

3. Facilitate a card sort about different activities that help or prevent germs from spreading.

• Introduce the card sort. Explain that students will consider how different everyday activities help or prevent germs from spreading, so they can apply these ideas to their hypotheses about why germs make us sick more often during the winter.
• Distribute the Spreading Germs Card Sort handout and scissors to pairs or small groups of students. Review the directions and circulate as students work together, being sure to:
• Attend to students’ thinking and ideas in preparation for the next step that relates their learning to the unit driving question.
• Prompt students to explain their reasoning, especially for activities that they identify as “it depends” in terms of spreading germs.
• Check that students question whether the activity is done in close or far proximity from other people. To relate to the unit driving question that will be revisited formally in the next step, they may also connect that some activities (playing in the snow versus swimming at the pool) are more seasonal or weather dependent.
• Encourage creative ideas for other activities that help prevent germs from spreading.
• Invite students to share out their categories or circulate to see their peers’ categorization and activity ideas.
• Ask students to find common themes across the categories, emphasizing how activities that help germs spread involve people being in close contact versus activities that keep germs from spreading involve people being distant from each other. Talk about how the climate/weather/season influences these activities and favor spread of germs

4. Connect students’ learning to the unit driving question by revisiting their initial hypotheses about why germs make us sick more often during the winter.

• Remind students of the unit driving question: Why do germs make us sick more often during the winter?
• Have students access their individual Question Quadrant handout from the Sick Days activity.
• Ask students to generate any new questions they have; especially for this activity, they may have new questions for the People quadrant, such as:
• What are other ways people help or keep germs from spreading?
• What else can we do to keep from getting sick?
• Are some of these activities easier to do or avoid than others?
• Next, have students revisit their initial hypotheses related to the unit driving question. To learn more about this practice, see Tips.
• Direct them to add ideas from this activity (and the Germs All around Us activity) on sticky notes or in a different color than their original hypotheses.
• Prompt students to consider if the new ideas support or counter their original hypotheses about why germs make us sick more often in the winter.
• Students may respond: I originally thought that germs made us sick more often in the winter because they use our bodies to keep warm in the cold temperatures. Now I think the fact that people are together more often in the winter may play a role, which is different than my original idea.
• If their thinking has changed, have students write their new hypothesis on their Question Quadrant handout.
• Debrief and synthesize student thinking by returning to the class Question Quadrant chart and revisiting the class’ initial hypotheses.
• Discuss each quadrant sequentially, starting with Environment and then People.
• Document students’ new thinking with sticky notes or a different color than their initial hypotheses.
• Explain that in the next activity, Bad Germs: Keep Out!, students will generate new ideas for the Germs and People quadrants as they explore more about how our bodies try to keep germs out.

5. Advance students’ work on the unit project by modeling how to write trivia questions for the Germology Game Show.

• Redistribute students’ individual Trivia Question Builder handouts. Explain that you will model how to use the ideas in this activity to create trivia questions and evidence-based answers, in preparation for students doing so on their own in following activities.
• Ask for volunteers to share: What new facts or ideas from this activity do you want to share with your community through the Germology Game Show?
• Record students’ facts and ideas in a public document, such as on the class whiteboard or chart paper.
• Select one fact or idea to model how to write a trivia question and evidence-based answer. Choose a fact/idea that is especially common among students, relies on a key piece of evidence, or would be of interest to adults and kids in their community.
• Follow the steps on the Trivia Question Builder handout as you record your process of developing a question, answer choices, and scientific explanation for each answer choice.
• Talk through your thinking process, emphasizing how to communicate about cause-and-effect relationships between different factors related to Germs, People, Environment, or Something Else.
• Invite students’ ideas to model the kind of collaborative process students should use when developing questions with different partners and group members throughout the unit.
• If relevant, explain how supporting evidence for the answer choices could come from ideas or visuals from the brainstorm in Step 1, the demonstration and data in Step 2, or the card sort in Step 3.
• For example, you may say: We decided people in our community really need to know that sneezes carry germs much farther than they think. I think this would work best as a fill-in-the-blank question. The question could be, “Sneeze droplets can carry germs at the speed of ________ miles per hour and travel as far as ______ feet.” Answer choices could include “1, 10, 100, or 1000 miles per hour” and “7, 17, 27, or 37 feet,” with the correct answer being: nearly a hundred miles an hour and travel as far as 27 feet. For each answer choice, we could include the graphs of sneeze data and our measurements with our interpretation of what it means.
• Prompt students to review the question-and-answer choices that you wrote and determine if it will make sense and be interesting to someone in the community. If needed, have students help to revise the language or content to make it more accessible.
• Have students record the question, answer choices, and explanations on their handout, as the first question in the Spreading Germs Question Set.
• Save the recorded process to refer to as students write their own trivia questions in subsequent activities.
• Finally, lead the class in collaboratively writing a second question for the Spreading Germs Question Set, based on another interesting idea that students determine community members will find interesting or need to know.