Teaching students about germs and hygiene can sometimes feel abstract. After all, kids can’t see bacteria on their hands. That’s what makes this hand washing experiment so powerful. It turns an invisible concept into something students can observe with their own eyes. Better yet, it’s simple, engaging, and a little bit gross (which kids love!).
This hands-on activity is perfect for upper elementary classrooms and ties directly into scientific observation, inquiry, and real-world health habits.
Want to know the best part of this science experiment for kids? Seeing the results will actually motivate them to wash their hands!
Materials Needed
To complete this hand washing experiment, you’ll need just a few basic supplies:
- White bread
- Ziploc bags
- Spray bottle of water
- Tongs
- Marker (to label bags with)
Handwashing Experiment Directions
Here are step-by-step instructions for this handwashing experiment. You can also see this experiment in action and the results in the following video.
1. Create Your Control Sample
Use clean tongs to place one slice of bread into a Ziploc bag. This slice should not be touched by hands at all.
This slice is your control. In an experiment, a control is something that stays unchanged and is used for comparison. It helps students clearly see the effects of the variable. In this case, germs from hands and surfaces.
2. Test Unwashed Hands and Surfaces
Have students gently wipe a slice of bread on their unwashed hands.
You can also expand the experiment by wiping bread on high-touch classroom areas, such as:
- Door knobs
- Light switches
- Computer keyboards
This allows students to discover some of the dirtiest places in the classroom and may even encourage them to wipe down those surfaces more often.
3. Label and Bag Each Sample
Place each slice of bread into its own Ziploc bag. There should only be one slice of bread per bag.
Be sure to label each bag clearly (e.g., “control,” “unwashed hands,” “door knob”) so students can track results accurately.
4. Add Moisture
Lightly spray one spray of water into each bag.
Be careful not to overdo it! Too much water can affect the results.
5. Seal the Bags
Seal each bag tightly, removing as much air as possible. This helps create a consistent environment for mold growth.
6. Store and Wait
Place the bags in a warm, dry location for at least 48 hours. I also recommend using a dark place.
Great storage spots include:
- Closets
- File cabinets
You can leave the bags for several days. The longer they sit, the more noticeable the results will be.
What Students Will Observe
After at least 48 hours, students will begin to see mold growing on the bread.
Here’s what they’ll likely notice:
- The control slice will have little to no mold.
- Bread touched by hands or surfaces will show visible mold growth.
- Some slices may grow more mold than others.
- Mold may appear in different colors (green, white, black, etc.).
This happens because bacteria and germs from hands and surfaces transfer to the bread, creating the perfect environment for mold to grow. The more bacteria present, the more mold students will observe.
Different mold colors can also indicate different types of microorganisms, adding another layer of scientific discussion.
Why This Handwashing Experiment Matters
This hand washing experiment is more than just a cool visual. It delivers an important life lesson. Students quickly understand why washing their hands is essential for staying healthy when they see that bacteria on their hands caused mold to grow.
It also builds key science skills, including:
- Observation – noticing changes over time
- Prediction – guessing which bread will grow the most mold
- Data collection – tracking results across samples
- Understanding variables – comparing the control to the test samples
- Scientific reasoning – drawing conclusions based on evidence
Because students can see the results, the learning sticks in a meaningful way. An added bonus is that you can remind students of the experiment outcomes to get them to wash their hands more often!
Conclusion
The hand washing experiment is a simple yet powerful way to bring science to life in your classroom. With minimal materials and setup, you can create a memorable experience that reinforces both scientific thinking and healthy habits.
They say that seeing is believing. By the end of the experiment, students won’t just hear that germs are everywhere— they’ll believe it. And that understanding can lead to better hygiene choices long after the lesson is over.
