Education Standards
Criteria Matrix
Hazard Cerification Card
https://oercommons.org/courseware/lesson/109077
Notice - Wonder - Know Student Sheet
STEMify Your Classroom Supply List
Overview
In this lesson students will develop an evidence-based argument after investigating the product safety, performance, and cost of a variety of cleaning and disinfecting products designed to remove germs. Students will be introduced to principles of sustainable design, life-cycle thinking, and how to identify safer products to certifications.
Except where otherwise noted, this work by Saskia van Bergen (Washington Department of Ecology), Vickei Hrdina (ESD 112), and Carissa Haug (NCESD) is licensed under Creative Commons Attribution License 4.0. All logos and trademarks are property of their respective owners.
Lesson Plan
STEM-ify Your Class Supply List
Lesson Overview:
In this lesson students will develop an evidence-based argument after investigating the product safety, performance, and cost of a variety of cleaning and disinfecting products designed to remove germs. Students will be introduced to principles of sustainable design, life-cycle thinking, and how to identify safer products to certifications.
Lesson Objectives -
Germs are bacteria. Bacteria are present everywhere and in/on all living things.
Products can be used for different purposes; cleaning, sanitizing, or disinfecting.
Choices in cleaning products come with benefits and tradeoffs. We can design investigations to help us make better decisions.
Scientists use evidence to make claims.
This lesson addresses the following Next Generation Science Standard Performance Expectation. In particular, ETS1.C:
Materials:
Clorox Disinfecting Wipes or another brand that has quaternary amines* as the active ingredient
GreenWorks Compostable Cleaning Wipes or another brand of wipes on the Safer Choice product list or if you want to test a sanitizer or disinfectant from the Design for the Environment Product list
Paper Towels
Microfiber Cleaning Cloth
GloGerm Powder
Brush
Masking Tape
Marker
Pre-filled LB plates and sterile swab kit
Engage:
Procedure
Read, “Do Not Lick This Book” https://www.youtube.com/watch?v=U43kKGtgYBE
Or another favorite book about germs.
Ask students what they noticed and what they are wondering about after reading the book? Accept all responses.
Ask students “What are different ways to clean a surface of germs?”
School-Home connection - “What ways do you or your family clean surfaces at home?”
(Potential student responses: soap and water, wipes, spray)
Tell students that they will be working like scientists to determine what cleaning product is best to remove germs from a surface.
Explore:
As a class or individually, write a plan for how to determine the best cleaning product for removing germs. Show students the materials that are available for their investigation.
Ask students to work together in small groups to come up with steps on how they think they can test for the cleaning product that removes germs the best.
Bring class back together and build a class procedure for completing the investigation using student input. As ideas are shared, be sure to point out fair test ideas and good scientific practices.
Follow the Physical Removal Activity and complete the investigation.
Use a Scientist’s Circle Discussion to have students share their observations from the physical removal activity.
Scientist Circle - Begin with Notice and ask one student to share just one of their observations. Ask other students if they have a notice that is similar or connected to the one that was previously shared. That student will then share their notice. Continue to work through the discussion allowing all students to share their notice. Then move on to Wonder and Know observations.
Lead students in a discussion to come to a consensus, based on evidence, of what cleaning product appears to do the best at removing germs. Record the consensus claim on chart paper to refer to later.
Follow the Disinfecting Activity and complete the investigation.
**PLAN AHEAD - This investigation takes several days for bacteria to grow in order to collect data.
Ask students to carefully walk around to other groups’ petri dishes and make observations. Have them note similarities and differences between their own petri dishes and other groups’ petri dishes.
Discuss as a whole class what they notice and determine if a consensus can be made regarding the best cleaning product for killing germs.
Discuss the difference between cleaning, sanitizing, and disinfecting.
CLEANING removes dirt and most germs.
SANITIZING reduces germs to safe levels.
DISINFECTING kills most germs, depending on the type of chemical, and only when used as directed on the label.
*You can learn more at Washington State Department of Health’s website
Explain:
Draw students attention to the focus question, “What cleaning product is best to clean a surface of germs?” Tell students they are ready to make an initial claim based on their investigation evidence.
Tell students that scientists use claim, evidence, and reasoning to communicate their scientific explanations to a question or problem. A claim is a statement that you believe to be true that answers the scientific question. Evidence is the data or research gathered through investigations, readings, videos, or observations. Reasoning shows how the evidence answers the question or solves the problem. *Consider creating an anchor chart for students to refer to for C-E-R.
Remind students that this is their initial C-E-R response to the focus question and that they will be learning more in the future so will be able to revise them.
Ask students to share their C-E-R with a partner, provide and receive feedback, then make any necessary revisions
Elaborate:
Ask students if they think it is necessary to kill germs (disinfect) from a counter versus only physically removing them. Have them turn and talk before asking for student responses. Remind students of the difference between cleaning, sanitizing, and disinfecting, if necessary.
Ask students, does removing or killing germs on a surface reduce the risk of disease? Could other actions be just as, or more, effective? Discussion could center on routes of exposure, effectiveness of surface washing for airborne diseases, effectiveness of handwashing for surface-borne diseases, the role of a healthy immune system and the impact of certain chemicals on the immune system.
Ask students if they can think of reasons why we might not want to use products with harmful chemicals in the classroom.
Tell students that scientists try to design chemical products that reduce or eliminate the use of hazardous substances. These scientists are called green chemists.
Provide students with the Hazard Assessment and Certifications Card. Tell students that sometimes there are products that are safer to use because they are less hazardous for the environment and living things. We can look for symbols like the Safer Choice symbol and the Caution labels to learn more about a product.
Ask students to look at the GreenWorks wipe container and identify its label using the Hazard Assessment and Certifications Card. Ask for a student volunteer to share their findings.
Ask students to look at the Clorox wipe container and identify its label using the Hazard Assessment and Certifications Card. Ask for a student volunteer to share their findings.
If using a spray product, ask students to look at the spray container and identify its label using the Hazard Assessment and Certifications Card. Ask a student volunteer to share their findings.
Ask students to talk to a partner about which product is less hazardous for us to use: Clorox, GreenWorks, or the microfiber cloth.
Handout a Criteria matrix to each student. Tell them this graphic organizer will help them develop an evidence based argument for what cleaning product is best for their classroom supply list.
Ask students to help you fill in the matrix with information from their investigations and from the labels on the cleaning products. At this point, you can fill in just the Safety and Performance columns with students' input. You will need to provide students with cost evidence. Example shown below.
Tell students that green chemists not only consider the hazards of a product but also its life cycle. Ask volunteers what they know about life cycles.
Tell students things like cleaning products also have life cycles*. When considering the life cycle of a product like the wipes, scientists think about what materials are needed to create that product, where those materials come from, who will be impacted by the use of those materials. They also consider who will use the products and how they might be impacted as well as what happens to the product when it is done being used.
Ask students, “What did we do with the cleaning products we tested in our investigations?”
(Potential student responses: threw the wipes away, put the microfiber cloth back in the cabinet)
Ask students to consider which cleaning product seemed best based on what happened to it after it was used.
Support students in filling out the final column in their criteria matrix.
Discuss as a class what students see in their criteria matrix. Ask them to think about what recommendation they would make regarding cleaning products and why they would make it.
Evaluate:
Tell students that being a scientist means communicating their research and findings with others. They will now be responsible for recommending a cleaning supply for the class supply list based on their research.
Have students use chart paper to create a poster with their cleaning product recommendation for the class supply list which should be based on their evidence. Students should use their criteria matrix to develop their argument.
Ask students to post their posters around the classroom for a Gallery Walk. One team member from the group will serve as the spokesperson and stay behind at the poster to answer questions for other students. The rest of the group will move around the room to observe other groups’ posters. The group will share what they learned from others with their spokesperson when they complete their *If this is the first time your students are engaging in a Gallery Walk be sure to establish norms around what this looks like and practice how to ask questions and provide feedback to others.
Complete the lesson by asking the class for a letter recommendation for cleaning supplies for the future class supply list based on their poster information. (Literacy connection- writing a letter)
Extension Activities:
Determining Effectiveness of Disinfectants
Ask students to use the EPA’s N list to investigate the effectiveness of the different disinfectants that are found in various commercial wipes like Clorox. EPA List N Tool
EPA’s Video Tutorial on How to Use the List N Tool
Promoting Safer Certifications for Communities and Families
Have students design a marketing material (poster, placard, etc) that promotes consumer awareness around Safer Certifications for places like supermarkets and stores.
Have students present their developed material to the class.
Washington State Department of Ecology’s Safer Choice Blog as an example
*Extension Life Cycle Activities
Sustainable STEM Lesson 03 Life Cycle
https://www.beyondbenign.org/curriculum_topic/ms-sustainable-stem/
Are Mushrooms the New Plastic? https://www.beyondbenign.org/curriculum_topic/ms-enrichment-resources/
‘Flusable” wipes causing problems in Tacoma (Unintended Consequences) Video (~3 minutes): https://www.youtube.com/watch?v=pJJvfF9XzeE
Flushable Wipes - Do They Disintegrate? Video (~22 minutes): https://www.youtube.com/watch?v=_iASfS9esVU
Do Flushable Wipes Actually Dissolve? Video (~12 minutes): https://www.youtube.com/watch?v=zAeRXSsVL-4
Physical Removal Investigation Procedure
STEM-ify your Class Supply List
Physical Removal Investigation Procedure
Materials
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Before the Activity
- Using a brush, apply GloGerm UV powder onto the surface that will be studied. Check with the UV flashlight that the material is dispersed.
- Mark laboratory stations using masking tape to demark 4 quadrants.
- Clearly label the 4 quadrants: Unwashed (control), Clorox Wipe, GreenWorks wipe, wet microfiber towel[a][b]
With students
- Instruct students to choose one student in each group for each of the following roles: the Supervisor (makes sure the washer wipes quadrants consistently) and the Washer (performs the washing and sanitizing of the sample quadrants).
- Teacher or student shines the UV flashlight on the quadrants.
- Instruct the Washer, to carefully and consistently wash the second quadrant with a Clorox Wipe. Be sure to have them wipe in a consistent manner (“s” wipe or 3 circles). Dispose of the wipe.
- The Washer repeats the process for Quarants 3 and 4 (GreenWorks and Microfiber cloth).
- Teacher or student shines the UV flashlight on the quadrants.
Data Collection and Analysis
- Have students in the group each document their observations and compare the quadrants. Notice - Wonder - Know Student Sheet
- Have each group present their observatory notes.. What do they notice? What do they wonder? What do they know? In a Scientist Circle Discussion
Safety Issues
UV Flashlight- Do not shine into eyes. Always avoid contact with eyes.
Extension Opportunities
- Using Glogerm for handwashing- https://www.instructables.com/id/Teach-a-Glo-Germ-Lesson-for-Improved-Hand-Washing-/
- Handwashing- water temperature, time, soap https://learning-center.homesciencetools.com/article/glo-germ-projects/
- Glogerm- Educational Worksheets (http://www.glogerm.com/worksheets.html)
[a]should we mention that they can use other things like paper towels and spray cleaning products?
[b](if they want to test other products)
Disinfecting Investigation Procedure
STEM-ify your Class Supply List - Microbiology
Disinfecting Investigation Procedure
Materials
Prefilled LB plates and sterile swab kit from Amazon ($20 for 10 plates)
Clorox Disinfecting Wipes or another brand that has quaternary amines as the active ingredient
GreenWorks Compostable Cleaning Wipes or another brand of wipes on the Safer Choice product list or if you want to test a sanitizer or disinfectant from the Design for the Environment Product list
Microfiber cleaning cloth
Before the Activity
Prepare LB plates (or use pre-filled agar plates)
Preparation instructions:
Add 10 g LB agar to 250 ml water in a microwaveable container.
Microwave the solution for about 3 minutes (until boiling).
Pour the hot solution into the Petri dishes, so that you just cover the bottom completely.
Let Petri dishes stand for 20 minutes while the agar solidifies.
*(Note: 250 ml LB solution will make 30 Petri dishes; adjust quantities appropriately depending on how many dishes you want to prepare.)
Label 4 Petri dishes for each group by using a marker to write the group number/name and class on the lids.
Mark laboratory stations with students using masking tape to demark 4 quadrants.
Clearly mark the following on each of the 4 lids: Unwashed (control), Clorox Wipe, GreenWorks wipe, wet microfiber towel
With students
Instruct students to choose one student in each group for each of the following roles: Swabber (collects the swabbing samples), the Supervisor (makes sure the correct Petri dish is being used) and the Washer (oversees the washing and sanitizing of the sample quadrants). Note: To reduce experimental error, it is important to have all samples come from the same person.
Show students the video procedure on how to use swabs in the petri dishes https://www.youtube.com/watch?v=C4COfoS8Y6Y
Hand out 4 pre-labeled Petri dishes to each group; ask students to notice how each lid is labeled.
Direct students to begin with the "unwashed" Petri dish. The Swabber, should gently rub a cotton swab on the surface of the quadrant. Be sure the Swabber does not lay down the cotton swab.
The Supervisor should open the "unwashed" Petri dish containing agar.
The Swabber should gently rub the cotton swab sample taken from the unwashed quadrant back and forth on the agar. Remind Swabbers to be very careful not to apply too much pressure when doing this, so as to not tear the agar.
The Supervisor should close the Petri dish.
Instruct the Washer, to carefully wash the second quadrant with a Clorox Wipe. Be sure to have them wipe in 3 circles. Wait at least 30 seconds (this is the dwell time that it takes for the product to be effective). Dispose of the wipe.
The Swabber and Supervisor should repeat steps 4-6 for this quadrant; being careful to streak the dish labeled "Clorox."
The Washer repeats the process for Quarants 3 and 4 (GreenWorks and Towel).
Swabber takes samples from each Quadrant.
Supervisor is to keep each dish labeled accurately and places them in a safe area for observation.
Data Collection and Analysis
Allow the plates to sit in a well-vented, warm area (not direct sunlight) for 4 days. At the end of each day, instruct Supervisors from each group to take a photo of their group’s quadrants and save them to a digital file.
Each student in the group should document their observations at the end of each day.
On the 5th day, have each group present their observatory notes and the photos of the bacterial growth. What do they notice? What do they wonder? What do they know?
Safety Issues
As soon as the plates have been streaked and the Petri dish lid replaced, apply two pieces of tape to keep the lids connected; however any closure should not be made air-tight.
Keep the Petri dish plates away from students until the time of data analysis. No student, at any time, should touch the agar or the bacteria. When taking pictures, open the lid briefly and replace it immediately.
When the activity is complete and pictures have been taken of all samples, immediately discard the Petri dishes in a trash container that is securely away from the student population.
Troubleshooting Tips
For optimal bacterial growth, place the Petri dishes in well-ventilated warm locations, between 22 ⁰C (72 ⁰F) and 37 ⁰C (99 ⁰F.)
Extension Opportunities
For ways to expand this activity see “Bacteria are Everywhere!” lesson at https://www.teachengineering.org/activities/view/nyu_bacteria_activity1