Hand-Washing Science

This experiment will show why you should always wash your hands before handling food. Using sliced bread, you’ll see how much mold grows after you touch the bread with dirty and clean hands. How different do you think they’ll be? 

3 slices of bread* 
3 (or more) resealable plastic sandwich bags
Spray bottle 

* Any kind of bread works, but store-bought white bread contains preservatives, which will slow down the growth of mold. For best results, use preservative-free wheat bread, bakery-fresh white bread, or homemade bread. 

Note to adults: This activity involves growing mold on slices of bread. Once sealed, the plastic bags should not be opened. When the experiment is finished, throw the bags of bread away. 

Label the three bags “control,” “clean hands,” and “dirty hands.” If more than one kid is doing the experiment, let them each create “clean” and “dirty” bags of their own.

Without touching the bread with your hands (you can use tongs or clean rubber gloves), place one slice of bread in the “control” bag and seal the bag. To speed up mold growth, you can sprinkle or spray a few drops of water on each slice of bread.

Before washing your hands, grab another slice of bread and touch it all over. Place this slice in the “dirty hands” bag and seal it up.

Wash your hands well with soap and water and touch the third slice of bread all over. Place this slice in the “clean hands” bag and seal it up.

Ask an adult to place all three bags in a cupboard or in your garage (away from pets and young children). Check on your bread daily and note any changes—you can also take a daily picture. After several days, you should start to see some mold. Which slice of bread grew mold the fastest? Throw the sealed bags away when you’re done with your experiment. Do not open them or touch the moldy bread.

WHAT HAPPENED? The stuff that grew on your bread is mold, which is a fungus related to yeast and mushrooms. Mold love to grow in warm, moist places—like a bag of bread. Mold spores are everywhere but invisible to your eye, as are the kinds of germs that make us sick—though the two are not the same. Washing your hands removes the mold (and germs) from them—at least for a short time. This is why it’s important to always wash your hands before you cook or eat.

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