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This is a well-developed lesson on good/bad bacteria and the proper way to wash hands


P.E. & Health, Science  


4, 5  

Title – Bacteria: Friend or Foe
By – Katie Kaufman
Primary Subject – Science
Secondary Subjects – Health / Physical Education
Grade Level – 4-5

Teacher Materials:

  1. Pictures of bacteria
  2. sink, soap, paper towels, waste basket
  3. hand washing diagram
  4. hand washing checklist ( 1 per student )
  5. pen/pencil

Student Materials:

  • Pencil
  • materials for experiment
  • hand washing diagram
  • sink, soap, paper towels, waste basket
  • evaluation sheet ( quiz )


  1. Given a pencil and paper, the student will be able to write two/three sentences describing what bacteria are in there own words. For their definition/description to be correct, they must say that bacteria are single celled organisms.
  2. From memory, the student will be able to list three ways that bacteria can be helpful.
  3. From memory, the student will be able to list two ways that bacteria can be harmful.
  4. Given soap, warm water and paper towels, the student will be able to properly demonstrate how to wash hands as learned in the lesson. Student should not miss any steps.


    Play a guessing game with students. You will describe something and they have to guess what you are describing. Don’t give the whole description at once, but as you describe, let students guess.


    1. Something that is alive.
    2. There are approximately five million trillion trillion of these on the earth.
    3. These things multiply very rapidly. They can double as quickly as ten minutes.
    4. Can live in live in extreme temperatures. Some have been found to live in under water volcano vents where it gets as hot as 700ºF and others live at the South Pole in temperatures as cold as – 120 ºF.
    5. These live almost everywhere. They cover everything, including your skin. They live in water, dirt, food, and in the air. They live inside you: in your mouth, stomach, and lungs.
    6. Some live in radioactive ( nuclear ) waste.
    7. Is so small we can only see it with a microscope.

      Answer : Bacteria


    “Today we are going to learn about bacteria.”

Sequence of Activities


      “Bacteria are living things that have only one cell. There are many different species of bacteria. Here are some pictures of bacteria magnified many, many times.” (

Show students pictures of magnified bacteria. Point out that bacteria are different shapes.

      “Do you think that bacteria are good or bad?” (

Let students answer

      “Actually, that was a trick question. Some species of bacteria are harmful and some are good.”

Discuss ways bacteria can be harmful and the solution/prevention of these problems.

      • Food poisoning : Food contains bacteria. If food is not stored at the proper temperature then the bacteria multiplies very rapidly. If this food is eaten it can cause nausea, vomiting, diarrhea, or in serious cases, death. Food poisoning can also be caused by eating food that is not cooked properly, like chicken or eggs. When food is cooked, harmful bacteria is killed ( bacteria is not the only cause of food poisoning ). E. Coli, Salmonella are more well known bacteria in food.

        Cook food thoroughly, especially meats. Refrigerate foods.

      • Bacterial Infections : includes strep throat, ear infections, pneumonia, and bronchitis. These are different from viruses. If treated properly, they are not life threatening, but if not treated can spread to other organs in the body.


      • Acne : caused in part by infection of bacteria in pores.

        do not touch face and spread bacteria to face; wash face

      • Cavities : caused by bacteria that eat sugar and convert it into acid plaque eats at tooth enamel.

        brushing teeth and flossing

      • Body Odor : when we sweat, bacteria begins to multiply rapidly n the warm, moist skin. The bacteria quickly multiply, then dies, releasing an odor as they decompose or rot.

        washing daily and wearing deodorant.

Discuss ways that bacteria are helpful.

      • Bacteria in the digestive systems of people and animals help break down food so that nutrients can be used and the waste disposed off. Good bacteria can fight of bad bacteria in the digestive system.
      • Bacteria help garbage and sewage to decompose. If there were not bacteria, there would be huge piles of garbage?
      • Dead Bacteria are used to produce antibiotics, and vaccines which help our bodies fight of bad or harmful bacteria.
      • Some bacteria produce oxygen.


    “The amount of good bacteria in the world far out numbers the amount of bad bacteria. Bacteria are necessary for human life. We just need to be careful not to spread bad bacteria. One simple way to prevent the spread of bacteria is hand washing.”

Experiment-Rub-A-Scrub: ( see handout below)

Hand Washing Activity:

      Give students hand-washing diagram. Verbally go over each step with them. Take students to a sink and demonstrate hand washing with the following steps (

verbalize steps as you demonstrate

        1. Wet your hands with warm water. Leave the water running.


        2. Use soap.


        3. Scrub hands well for about 20 seconds. Make sure to scrub under fingernails where bacteria like to hide and multiply!


        4. Rinse well. Make sure to rinse all soap and dirt down the drain.


        5. Dry hands.


      6. Use the paper towel to turn of water, so hands do not become re-contaminated. Also, use the paper towel to open the door if it has a handle of knob. Throw paper towel in a wastebasket.

Evaluation of Students:

    Have students demonstrate hand washing according to the steps taught above. Use a checklist to grade each student. Student should not miss any steps.


      Review the material covered in lecture with question and answers.
      Q: “How many cells are in one bacterium?”


      A: “


      Q: “Where are bacteria located?”


      A: “

They cover almost everything; they are inside of your mouth and digestive system, in air, water, dirt

      Q: “How big are bacteria?”


      A: “

They are so small that we can only see them with a microscope

      Q: “What is one way bacteria are harmful?”


      A: “

Body odor, infections, food poisoning, cavities, etc

      Q: “What are some ways that bacteria are helpful?”


      A: “

Help waste to decompose, make oxygen, help food digest, used to make medicines

      Q: “Are there more helpful or more harmful bacteria?”


      A: “

more helpful


Evaluation of Students:

      Students take a quiz to see what they learned about bacteria. (

See below


Sources of Information:

  1. Wikipedia, the online encyclopedia; articles: Microorganisms, Bacteria 
  3. The weather notebook:
  4. What are Germs? 
  5. Best of Mailbox Science Grades 1-3; © 2006, The Education Center, Greensboro, NC


Name: _______________________________________


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