Hands Off, Bacteria!
This lab challenges students to identify the variables involved in handwashing. They will design labs to discover the best method for washing their hands to reduce the spread of bacteria. Students will also analyze and present the data. Grades 6-8
- Glo GermTM and ultraviolet light
- Handwashing soap
- Paper towels
- A source of running water
- Petri dishes with nutrient agar and covers for each team of 3 to 4 students (optional)
- Dr. X and the Quest for Food Safety video, Module 4 — Retail and Home
- Gather a collection of materials for students to use in their lab designs.
- Put Glo Germ™ (or cooking oil and cinnamon) on your right hand just before the students enter the classroom.
foodborne illness: any illness resulting from the consumption of food contaminated with viruses, parasites, or pathogenic bacteria
Did You Know?
- 20% of consumers don’t wash their hands before preparing food.
- If you don’t wash your hands, you could cause infant diarrhea! Your hands can pick up bacteria from the following things and spread bacteria to a baby:
- Raw meat, poultry, eggs, and seafood;
- Animals such as dogs, cats, turtles, snakes, and birds; and
Background Agricultural Connections
Dirty hands are one of the quickest ways to spread harmful bacteria and expose yourself and others to the risk of foodborne illness. Careful attention to washing hands thoroughly is essential for good health.
Safety Precautions for this Lab:
- Wash your hands before and after the lab.
- Seal all inoculated Petri dishes with Parafilm. Remind students never to open a dish with organisms growing in it. Some organisms could be dangerous pathogens.
- Destroy all disposable Petri dishes using safe techniques after the lab is completed, or soak each used Petri dish in a bleach solution.
- Disinfect all lab surfaces before and after working in the lab.
Science and our Food Supply
This lesson was developed as a portion of an entire unit of lessons focusing on food safety from farm to table. Use the following links to see the remaining lessons:
Module 1: Bacteria
Module 2: Farm
Module 3: Processing and Transportation
Module 4: Retail and Home
- Supermarket Smarts
- Cooking Right: The Science of Cooking a Hamburger
- A Chilling Investigation
- Crossed Up!
- Hands off, Bacteria!
Module 5: Outbreak and Future Technology
Evaluation: Lose a Million Bacteria (The Game)
- Greet each student with a hearty handshake as he/she enters the classroom. (Only you know at this point that Glo GermTM is on your hand.) When the students get settled, ask them:
- When was the last time you washed your hands?
- What have you touched since then? What have you touched in the past 2 hours? In the past 4 hours?
- Do you think your hands have picked up bacteria recently? (Let the students discuss the things they touched in the last few hours. Hopefully, someone will remember that you shook everyone’s hand.)
- Could I have spread bacteria to your hands through my handshake? Let’s find out. (Now take out the ultraviolet light and let the students examine their hands and classroom surfaces.)
- How many people or surfaces have come in contact with my “bacteria” without coming in contact with me?
- Would you want to eat a sandwich made by people who didn’t wash their hands? Why?
- Have you ever seen signs in restaurant bathrooms stating, “Employees must wash hands before returning to work”? Why are these signs so important? (One of the most common ways to transmit foodborne bacteria is by using the bathroom, not washing your hands properly, and then touching food.)
- Note: For a real-life outbreak case involving a foodworker who did not properly wash his hands, see the lesson plan, Outbreak Alert.
- We know that handwashing is extremely important. Today we’re going to do a scientific investigation to learn more about the role handwashing plays in helping to keep us healthy and our food safe. Let’s begin our investigation ...
Explore and Explain
Part 1: Conduct the Lab
- Ask students the following questions:
- What are some of the different variables involved in handwashing? (Washing or not washing, using soap or no soap, the time spent washing hands, the temperature of the water, scrubbing hands versus just rinsing.)
- Have students develop a lab to discover the best method for washing their hands.
- How could we test whether or not handwashing has been effective? (To determine the most effective handwashing techniques, you can use Glo Germ™ and an ultraviolet light or cinnamon and cooking oil to represent “bacteria.” Students can test which of the following actions gets rid of the most bacteria:
- Cold versus warm versus hot water
- Scrubbing versus not scrubbing hands
- Using soap versus not using soap
- Length of time spent scrubbing (20 seconds is the recommended amount of time for effective handwashing)
- Note: Students can also use Petri dishes to sample hands before and after handwashing.
- Have students form teams of 3 to 4 students. Ask each team to design a lab or activity to investigate handwashing. They can choose to show how germs are spread by poor handwashing habits, the effectiveness of different handwashing techniques in reducing bacteria, or they can investigate their own handwashing hypotheses.
- Have students write down their research questions, hypotheses, and the procedures they plan to use. Challenge them to include the scientific principles behind their hypotheses and findings.
- Let each team present its hypothesis and experimental design to the class. Encourage all students to discuss the merits of each suggested test. After the class discussion, give the teams time to revise their hypotheses and experimental designs if they wish to.
Part 2: Conduct the Lab and Record and Report Results
- Have students conduct their labs.
- Ask students to observe and record results, then create a chart or graph to show their data. Complete the lab by having the teams write their conclusions.
- Have the teams present their results. Encourage students to include any problems they may have had and what they would do next time to avoid those problems. Remind them to explain the science behind their discoveries.
- Let’s rejoin Dr. X to see why he’s so concerned about a problem in Sector 17.
- Prepare students for the video clip by telling them that they will be finding the answers to these questions:
- The Barkley family learned about the importance of washing their hands. What could have contaminated their hands before they sat down to eat dinner? (Playing with the dog, sneezing into hands, taking out the garbage, playing basketball.)
- Why is handwashing so important both at home and in the retail setting? (Our hands are in contact with bacteria in all settings. It’s necessary to wash them just before food preparation, whether at home or in a retail setting.)
- Can you think of other things that you touch that contribute to the spread of bacteria? (Students should contribute their own answers.)
- Show video Module 4, Part 2 — Home (Time: 2 minutes).
Create a brochure on handwashing for young children.
Review the following questions:
- How do bacteria spread? (They can spread from person to person, from people to foods and objects.)
- What methods worked best to remove “bacteria” from your hands?
- Why do certain methods (e.g., scrubbing time, use of soap, etc.) work better to remove bacteria than others?
- Did your lab give you any ideas for conducting further research on handwashing?
Hands are one part of the body that are most exposed to microorganisms because they touch many things every day. Thorough handwashing with hot, soapy water removes bacteria from hands.
The Science and Our Food Supply Curriculum was brought to you by the Food and Drug Administration Center for Food Safety and Applied Nutrition and the National Science Teachers Association.
- FDA Education Team Leader Food Safety Initiative: Marjorie L. Davidson
- FDA Science and Our Food Supply Project Director: Louise H. Dickerson
- FDA/NSTA Associate Executive Director and Science and Our Food Supply Program Director: Christina Gorski
- FDA/NSTA Science and Our Food Supply Program Assistant: Jill Heywood