Growing Germs


Growing Germs

By Adventure Science Center

BACTERIA! VIRUSES! GERMS! OH MY! Use this DIY Science activity to teach your young scientist about germs and the importance of hand washing.


  1. Germ–
    (noun) a microscopic living thing; especially : one that causes disease.
  2. Bacteria–
    (noun) any of a group of single-celled microorganisms that live in soil, water, the bodies of plants and animals, or matter obtained from living things and are important because of their chemical effects and disease-causing abilities.
  3. Virus–
    (noun) any of a large group of very tiny infectious agents that are too small to be seen with the ordinary light microscope but can often be seen with the electron microscope, that are considered either very simple microorganisms or very complicated molecules, that have an outside coat of protein around a core of RNA or DNA, that can grow and multiply only in living cells, and that cause important diseases in plants and animals including human beings.
  4. Microorganisms–
    (noun) an organism (as a bacterium) of microscopic or less than microscopic size.


  • 1-2 apples
  • 2-4 glass jars with lids
  • Tape
  • Marker or pen
  • Knife (to cut apples)
  • Hand soap


Label each of your jars with the following:

  • Control (the apple half that will not be touched)
  • Dirty (the half that will be handled with unwashed hands)
  • Washed without help
  • Washed with timer (set a timer for 20 seconds, watch to ensure your scientist’s hands are washed thoroughly)


  1. Cut two apples in half on a sanitized cutting board. Carefully place one apple half in a clean glass jar without touching it by sliding it off the cutting board with the knife and close the jar. This is your control apple that should help you to see the difference in decay between apples with germs and without.
  2. Have your young scientist pick up one of the apple halves and rub their hands all over it. Place that apple into the “dirty” jar and close.
  3. It’s time for a hand-washing session! Send your young scientist to wash their hands on their own. When s/he returns, it’s time to rub another apple half and place it into the “washed without help” jar.
  4. Wait a little while before doing the final apple half so your scientist’s hands can get dirty again. When you feel ready, join your young scientist for the second hand-washing session. Make sure to lather the tops and bottoms of their hands and between their fingers for a full 20 seconds before rinsing. Have your scientist rub their freshly cleaned hands on the final apple piece and place it in the final “washed with timer” jar.
  5. Place the jars in a safe place.
  6. Check on the apples regularly. There won’t be too much action other than a little browning for the first week or so. Eventually, you should start to see mold forming on the “dirty” apple. Compare the differences in the apples.

Now, if your young scientist ever argues against washing their hands, you can just ask them if they remember what you saw on the apple!

Questions to Consider:

  • Which is the dirtiest?
  • Which is the cleanest?
  • Did your “washed with timer” apple fare the best? If so, why do you think that is?
  • Does this make you want to wash your hands more often?




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