Germ Experiment — Where Do Germs Grow in Your House??!

Germ Experiment: I saw this germ experiment on Homeschool Share and knew we had to add this into our unit on First Aid. After all keeping ourselves healthy is as important as patching up the injuries, right?!

The experiment called for gelatin, sugar and petri dishes. We didn’t have petri dishes so used paper cups and covered them immediately with glad wrap in lieu of a cover.

  • Boil 1/2 cup of water
  • Add 2 tsp of sugar and 2 tsp of unflavored gelatin
  • Stir until dissolved. Spoon into the cups (I had about 1 cm or 1/4 inch of gelatin in each cup.)
  • Cover immediately with Glad wrap to keep it clean and as uncontaminated as possible.
  • Chill for 24 hours

The next day: Label each cup. Then go around the house with cotton swabs and choose areas to collect germs.  Take a swab of the area. Rub the swab gently on the top of the gelatin. We chose to swab the following: the toilet, a door knob, nothing (as a control), a plant, the kitchen sink, the inside of LD’s mouth.

Set it aside in a dark, warm place for 5 or 6 days.  I stuck mine under the sink in the guest bathroom.

The results really, really surprised me!  So, of all the things we did what do you think had the most germ growth?

  • the toilet,
  • a door knob,
  • nothing (as a control),
  • a plant,
  • the kitchen sink,
  • the inside of LD’s mouth

LD and ED thought the toilet would have the most germs.
DD thought the inside of the mouth would have the most germs.
Dad and I have seen shows and thought the kitchen sink would have the most germs.

And the winner was…

the plant!! (center pic) Followed by the
sink (top left) and door knob (top right)
and the mouth, toilet and nothing coming in 4th, 5th and 6th places.
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  1. by Gabriela

    On March 5, 2012 at 7:38 am

    Very cool!
    I’ve been looking for a science experiment that: doesn’t make too much waste, shows something that is actually important to see for real life purposes, doesn’t call for hard-to-get materials, and is easy to use with the scientific method. This is the one. Thanks!

  2. by Discovering Montessori

    On March 5, 2012 at 7:33 pm

    I would have guessed the toilet. This is a really cool experiment. We must do this!! Thank you for sharing.

  3. by Liesl

    On March 6, 2012 at 7:12 am

    I’m so glad to hear some people like this! I was so excited to share this post because the results were so interesting! Thanks for stopping by!

  4. by Thankful Becky

    On March 10, 2012 at 8:54 am

    I pinned your page!
    Love the germ experiment.
    Visiting from WUHS. :)

  5. by happycampers

    On March 28, 2012 at 2:40 pm

    Great article but one VERY IMPORTANT part is missing. After you take your samples and spread them on your petri dish, you need to either seal shut the lid, or if using cups put them in a zip lock bag AND DO NOT OPEN THEM EVER! You grew some awesome cultures, but you have no idea what they are. It is potentially dangerous to breathe in or handle unknown cultures. I would have never thought of this until I read that on a homeschool science supply website.

    Thank you for providing the culture growth medium recipe…we will use it!

  6. by Heather Fyffe Dunham

    On March 28, 2012 at 8:00 pm

    We’re totally going to try this. I think I’ll use my smallest mason jars. I’ll sanitize them first with either boiling water or a dishwasher cycle, just like if I were making jam. Then I’ll use the plastic screwtop lids for them.

  7. by Liesl Den

    On March 30, 2012 at 9:18 am

    That’s a great point about keeping the dishes covered. I didn’t think to mention that in this post. You do need to keep the mold covered and dispose of the cultures properly.

    Thanks for all your comments everyone!

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