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Catchy Title: Hands Off
Theme/Topic of Lesson: Microbial contamination on hands
Time Commitment: 4-45 minute periods
Subject Area(s):
Health - Environmental health
Science
Grade Level(s): 6,7,8
Standards Alignment:
Class Challenge Question: Why wash your hands?
and When washing, what is the most effective way to wash?
Overview:
In the news we hear about the dangers of eating too much of certain fish due to mercury, PCB, pesticide and other chemical accumulations. But preliminary research on urban fishing has revealed another and more immediate threat to human health: the presence of the microparasite Cryptosporidium on the surface of caught fish and on the hands of those that fish. These anglers then eat their lunches, wipe their eyes, etc. with those hands! Cryptosporidium, like some other microorganisms can cause severe intestinal disease.
What is an angler to do? One easy thing is what most mothers say: Wash your hands! There are many other reasons to wash your hands, but most are for the same reason--to get rid of germs.
In this lesson students perform a handwashing experiment to see if a difference can be detected in the number and types of microbes on our hands after various types of cleaning. Students will also demonstrate that they have learned the whys and hows of good handwashing.
This lesson teaches scientific inquiry and conducting a good experiment, but there are important health and environmental issues that are incorporated as well.
Students should be instructed in maintaining sterility of petri dishes and should have access to computers (ideally one/lab group but one for the whole class is okay if necessary) and they should know how to gather information from internet sites.
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Environmental Science
(K-12) | Maryland Content Standards Indicators
Students will use scientific skills and processes to explain the interactions of environmental factors (living and non-living) and analyze their impact from a local to a global perspective. | | Life Science
(K-12) | Maryland Content Standards Indicators
Students will use scientific skills and processes to explain the dynamic nature of living things, their interactions, and the results from the interactions that occur over time. | | Skills and Processes
(6-8) | Maryland Content Standards
Students will explain how the nature of science has affected scientific inquiry, technology, and the history of science. | Maryland State Indicators
1.8.16
modify ideas based on new information from developmentally appropriate readings, data, and the ideas of others. (MLO 1.2.6.) | Skills and Processes
(6-8) | Maryland Content Standards
Students will explain how the nature of science has affected scientific inquiry, technology, and the history of science. | Maryland State Indicators
1.8.14
provide supporting evidence when forming conclusions, devising a plan or solving a practical problem. (MLO 1.2.4.) | Skills and Processes
(6-8) | Maryland Content Standards
Students will explain how the nature of science has affected scientific inquiry, technology, and the history of science. | Maryland State Indicators
1.8.7
collect, organize, and display data in ways others can verify (i.e., numbers, statistics, tables, graphs, drawings, charts, diagrams) using appropriate instruments (e.g., calculators, spreadsheets, databases, and graphing programs). (MLO 1.1.6.) | Skills and Processes
(6-8) | Maryland Content Standards
Students will explain how the nature of science has affected scientific inquiry, technology, and the history of science. | Maryland State Indicators
1.8.4
recognize/develop well-designed procedures that identify the independent and dependent variables, the need for control when testing a factor, the importance of multiple trials, the selection of appropriate materials/equipment, and the development of clear, logical directions within an investigation. (MLO 1.1.4.) | Skills and Processes
(6-8) | Maryland Content Standards
Students will explain how the nature of science has affected scientific inquiry, technology, and the history of science. | Maryland State Indicators
1.8.8
analyze and summarize data to identify trends and form a logical argument about a cause and effect relationship or a sequence of events. (MLO 1.1.7.) |
Learning Objectives:
The Students will:
describe why handwashing is beneficial make a hypothesis about which handwashing method will result in the fewest organisms growing on a petri dish conduct an experiment which will test various handwashing methods, complete with multiple trials and controls record the results of the experiment and analyze the data to draw conclusions. discuss the limitations of the data and confounding factors which may have affected the results demonstrate effective handwashing
Assessment
Students will write a complete lab report to submit with the entire experiment, including question, hypothesis, (methods if teacher desires) data, results, conclusions and discussion.
An example of the lab report format is attached and a grading rubric is provided.
Each lab group will perform a skit in which they demonstrate good handwashing technique and why it is important.
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Resources
Materials
Per classhand soap
antibacterial soap
waterless hand sanitizer
paper towels
water
bleach
marking pens - Hands Off! Lab Report Scoring Rubric (View)
Per student team/group of 3-4petri dishes with nurtient agar (as few as 2 to 10 /group depending on size of groups, space and budget constraints:
Available from Connecticut Valley Biological Supply 82 Valley Road, PO box 326, Southhampton,MA 01073 phone 800-628-7748& - Hands Off--Handwashing How To--directions for creating the skit (View)
computer with internet access. Excel and RealPlayer if desired
Per StudentNot Specified
Vocabulary
- microparasite - an organism too small to see without a microscope which lives as a parasite on other organisms.
- parasite - an organism that lives on or in another host organism in a way that harms or is of no advantage to the host
- petri dish - a shallow dish with a cover usually used for growing bacterial cultures
- media - the nutrient mix in a petri dish which feeds the organisms growing there
- germ - disease causing organism
Procedures
Introduce the lesson by discussing issues students know of related to fishing and eating fish. They have probably heard about mercury accumulation, PCB's pesticides, etc. Ask if they think you can get sick by touching the fish. The chemicals won't usually make them sick just by touch, but the organisms that live ON the fish might. Ask students what they think can be done to prevent getting sick in this way--and lead them toward the simple solution of hand washing.
Ask if the students think handwashing really does decrease the "germs" on their hands. Have the students as a whole class, or in lab groups design an experiment testing the effectiveness of hand washing in decreasing bacteria on hands. Students will then carry out the experiment, collecting and recording data, calculating results and drawing conclusions. An important part of the conclusions will be recognizing the shortcomings in the data. In addition, students will do research on the web about handwashing. They can view results of a study similar to the one they did. They will also be responsible for learning proper handwashing technique, why it is important even if you are not going fishing.
Day 1: Hands On
Daily Challenge Question: What are some of the reasons to wash your hands?
How will we test if handwashing is effective?
45 minutes
Set-up Directions:
You will need petri dishes to show the students.
You will need the Hands Off! Lab Report and Scoring Rubric and the Materials and Methods if desired. The Lab Report can be saved as a document and completed on the computer, or the answers can be filled in on a separate page.
Teacher Presentation & Motivation:
Introduce the lesson by asking the students what they know about health issues associated with fishing.Students will probably know the risks associated with eating fish high in mercury, PCB's etc. Ask if they can think of any health risks associated with handling fish. Lead them to talking about fish that live in water polluted not necessarily by chemicals, but by wastewater and the associated microorganisms in the water, some of which can cause disease. Anglers eat their lunches, wipe their eyes, etc. with their hands after handling fish caught from these waters. Preliminary research has found that 100% of urban fisherfolk in the Baltimore area had the microparasite Cryptosporidium on their hands and 60% had enough on their hands to cause disease.Cryptosporidium can cause severe intestinal disease, with those who are immunosuppressed especially at risk for serious illness and even death. .
What are anglers to do? Let the students try to problem solve, and stress that fishing is an important source of food and protein for many urban families and so economically and nutritionally it would be very detrimental to stop eating fish altogether.In addition, it is urban waters that are most likely to be polluted by Cryptosporidium and other similar disease causing microorganisms.
Lead the students to handwashing as a possible solution to this problem and discuss what handwashing is reputed to do. (Get rid of germs, which are disease causing organisms). Ask students to think of ways in which they can test if handwashing actually accomplishes this. Show petri dishes with nutrient media, explain that bacteria grow on these and can be used to "see" what is on their hands after washing. At this point, students can be divided into lab groups to finish designing the experiment, the experiment can be designed as a class, or you can show the students the prepared Materials and Methods.
The most important things to remind the students are: the need for a control (not washing hands) and for repeated trials (more than one of each treatment). Students also need to decide what their treatments will be. Suggestions: water only, water+soap, water+antibacterial soap and a waterless cleanser. Remind students that once they have done one treatment (water+soap) they cannot do another one without getting their hands dirty again. The experiment can be conducted on a few successive days, or students be allowed to do another activity in between.
Once the experiment is designed, students should formulate a hypothesis and decide how they will collect and record data. It may be necessary to explain to the students what a petri dish is and how things look when they grow(often, but not always roundish "colonies" of bacteria). Unless the students have had experience(and even if they have), it is probably a worthwhile to discuss exactly what data will be collected: total number of colonies, number of colony types and numbers of each type, etc. etc. At this point you may also want to introduce them to possible sources of error and how to best protect against them ( dirty paper towel, soap has something growing in it, organisms on hands can't grow on nutrient media in petri dish(true of Cryptosporidium and viruses!!!), etc.) It is also important to have students formulate a uniform procedure for putting hands on petri dishes.
Activity 1 - Hands On
Students will discuss why they think handwashing is important. They will design an experiment to test various methods of handwashing. They will have formulated a question, developed a hypothesis and created a data table for use in the experiment.
Wrap Up:
Review with students information from the beginning of the lesson why handwashing is important. Make certain that every lab group (or the whole class) has completed a question, hypothesis and a data table. Let the students know when they will conduct the experiment so they come with dirty hands!
Day 2: Wash Away
45 minutes
Set-up Directions:
Students will need petri dishes with nutrient media. To reduce the number of plates needed each group can test one treatment or treatments can be replicated in other groups. A marking pen is needed to label the petri dishes.
Water and various soaps (regular, anti-bacterial, waterless hand sanitizer) and towels are also needed.
Teacher Presentation & Motivation:
Review question, hypotheses and procedures from previous day. Insure that all procedures are uniform. Clarify that each lab group is going to collect its own data and that the data from the class will be pooled in a data table. Have students carry out the experiment as described in their procedure or in the Materials and Methods. Explain to students that they should check the petri dishes each day for the next 7-10 days. If there is nowhere warm to keep the plates the organisms will take longer to grow. Try to keep plates in a warm, dark place.
Once students have completed the procedure have them record any observations and anything that happened (e.g. a petri dish fell on the floor and opened) that may affect the data they collect.
Activity 1 - Wash Away
Students will carry out the handwashing experiment.
Wrap Up:
Review the experiment as conducted and how data will be collected.This can be in hand drawn tables or in Excel. Give students an ending date (may depend on where the petri dishes are incubated) at which time final data will be collected, results recorded and conclusions drawn. Ask the students if they still have the same hypothesis as when they began.
Day 3: Living Hands
Daily Challenge Question: Which method of handwashing got our hands "cleanest"? What does cleanest mean in this experiment?
45 minutes
Set-up Directions:
petri dishes, set up previously
lab reports begun previously
access to computers with Excel (if completing data tables in Excel) and internet access.
scoring rubric
10% bleach solution in water to soak petri dishes in for 1/2 hour before disposal .
Teacher Presentation & Motivation:
This is the day when the students will collect data, record it for themselves and for the class. The lab report also requires a graph of the data from the whole class. The students are also expected to draw conclusions and use internet resources for the discussion portions. The results on the internet indicate that soap with chlorine, and not antibacterial soap, is better at removing bacteria than ordinary soap. Soap with chlorine is not ordinarily available in stores. Interestingly, the waterless hand sanitizers caused an increase in the bacterial numbers on hands. Have students try to decide why they received the results they did and why they were or were not similar to published reports. It would be helpful to discuss sources of error and discrepancy before having them write the lab report. Are there bacteria in the wash water? in the soap? on the towels? The type of bacteria on your hands before the experiment probably will affect the outcome as well. Some may be more susceptible to the soap and scrubbing, some may grow more easily on the nutrient agar. Repeat that not all organisms will grow on the agar.Viruses are a large category of disease causing organisms that will not grow.
After finishing with the petri dishes, soak them in a tub of water containing 10% bleach for 30 minutes to insure disinfection. They can then be thrown out in the trash.
Activity 1 - Results and Conclusions
Have students collect the data from their plates. You can use the data sheet provided or one of your own choosing. The main objective is to find some way the students can quantify what is on their petri dishes and draw conclusions. In the end it is easiest to count colonies, but you and your students can decide what works best.
Work with the students to interpret the data and draw conclusions. Have a large data table that the whole class can use to share the data. Even if each group has done their own experiment, this is useful and a good time to emphasize the advantages of multiple trials.
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Activity 2 - Discussion
Students will complete the Discussion section of the lab report, using the websites provides. They should have completed the rest of the lab report prior to this activity.
Focus for Media Interaction
Focus for Media Interaction: The focus for media interaction is a specific task to complete and/or information to identify during or after viewing of video segments, Web sites or other multimedia elements.
Students will look for results of similar experiments in the web sites. They will also look for information about the importance of handwashing.
Viewing Activities
What will your students be responsible for while viewing this piece of multi-media or video?
Students will answer the questions in the discussion section of their lab report using the information from the two websites listed. They can view the video clip on the CDC website if desired (Real Player is necessary to play it ), but the web site contains a transcript of the video.
Post Viewing Activities
How will students utilize the information they gathered while viewing the multi-media or video?
The students will have to make up a skit using this information in the next lesson.
Wrap Up:
Given their data and the information on the web, ask the students what they would recommend as the most effective handwashing system. Remind them how the discussion started--with the contaminated fish--and ask what they would recommend to the anglers.
Let the students know that the final activity they will do is to create a skit using this information during the next lesson.
Day 4: How to Handwashing
Daily Challenge Question: How can you present the information on handwashing to other students in a fun and informative way?
45 minutes
Set-up Directions:
Handouts:
How to Handwashing directions and scoring rubric.
props as needed by students for skits
Computers with internet access to review the websites
Teacher Presentation & Motivation:
Once the students have learned about handwashing this is an opportunity for them to teach others in a fun way. Let them use their imaginations to create a skit about why handwashing is important. They can use the websites they used for the Discussion section of the lab report. Other websites are listed with more information and resources for teachers.
Activity 1 - How to Handwashing
Students will present a skit about the benefits of handwashing and the proper technique. The elements which should be presented in the skit are outlined in the handout. The scoring rubric helps them understand what is expected of them.
Wrap Up:
Encourage the students to practice good handwashing and "spread the word" about the benefits of handwashing.
Enrichment Options
Parent-Home Connection
Have students keep track of when they and their family members wash their hands. See if the data agree with that presented in the websites.
Cross-Curricular Extensions
A few possibilities include:
The issue of fish and nutrition
Water contamination
Subsistence fishing and economic realities of families that depend on it.
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