Germ Growth Experiment

Objective: Collect and grow everyday germs to see how microbes develop over time.

Materials Needed

• 3 sterile Petri dishes with agar medium
• Sterile cotton swabs (or Q-tips)
• Permanent markers for labeling
• Ruler (optional, to measure colony size)
• Gloves (optional)
• Disinfectant wipes

Safety Guidelines

• Wash hands thoroughly before and after the experiment
• Do not open Petri dishes once they are sealed
• Wear gloves if skin is sensitive or if instructed by teacher
• Disinfect your workspace before and after handling materials

Procedure (20 minutes total)

1. Prepare and Label (5 minutes)

• Have students wash and dry their hands.
• Give each student one Petri dish and one swab.
• Instruct them to label the bottom of the dish with their name, date, and surface swabbed.

2. Collect Samples (5 minutes)

• Discuss possible surfaces: desk, phone, doorknob, computer mouse, etc.
• Students rub the swab gently across their chosen surface (2–3 strokes).
• Immediately streak the swab across one quadrant of the agar, lifting and placing it lightly in zig-zag motions.

3. Seal and Plate (5 minutes)

• Close the Petri dish lid and secure it with a single piece of tape.
• Gently rotate the dish to spread the sample; avoid shifting the agar.
• Wipe down the workspace with disinfectant when finished.

4. Incubate and Predict (5 minutes)

• Place dishes upside down in a warm, undisturbed area of the classroom (around 25–30°C).
• Ask students to predict which surface will show the most growth and why.
• Review that dishes must remain closed to prevent contamination.

Observation Chart

Students will fill in this chart over the next few days, noting colony size, color, shape, and pattern.

Dirty vs. Clean Hands Quick Draw

Take 5 minutes to complete this quick sketch and activate your knowledge about where germs like to hide on our hands.

1. Draw a large outline of your hand in the space below.
2. Use a red pen or pencil to mark (circle or shade) all the spots where you think germs might hide.
3. On the same outline or a second one, draw how a clean, well-washed hand looks.

Hand Outline(s):

Now answer:

• List two spots you often miss when washing your hands:

1. ___________________________
   
   
   
2. ___________________________
   
   
   

• What will you do next time to make sure those areas get clean?
__________________________________________

Handwashing Pledge

Name: ___________________________ Date: ___________________

I promise to wash my hands properly to keep myself and others healthy.

1. I will wash my hands when (check all that apply):
   ☐ Before eating ☐ After using the restroom ☐ After coughing or sneezing ☐ After playing outside ☐ Other: ___________________________
   
   
   

2. I will scrub for at least 20 seconds, focusing on these areas:

   • Between my fingers
     
     
     
   • Under my fingernails
     
     
     
   • Around my cuticles and thumbs
     
     
     

3. I will use soap and water (or hand sanitizer if soap isn’t available) every time I wash my hands.

Draw your clean, well-washed hands below (include bubbles or water splashes to show you lathered for 20 seconds):

My Signature: ___________________________

Thank you for keeping our classroom healthy! Hang this pledge where you will see it every day as a reminder to wash well and often.