Wednesday, March 18, 2015

Peeps Easter Science Experiments

Wondering what to do with some of your Easter candy - how about a bit of science?   We had a lot of fun testing our marshmallow Peeps and learning about some of their properties. In particular we tested what happened to a Peep in low air pressure, in different temperature water, and finally how temperature affected the Peeps structural integrity (or ability to withstand a hammer).  It was a really fun and hands-on set of Easter science experiments.

Peep Experiment 1:  Why is a Peep so light? {or changing air pressure}

First we wanted to know what made peeps feel so light.  So we carefully placed a test Peep into a mason jar and attached our vacuum sealer to the jar.  This allowed us to suck the air out of the jar and see what happened to our Peep.  The girls thought that the Peep would float in the air.

Instead our Peep grew and grew!

The girls were so surprised.  When we released the vacuum the Peep returned to its original size and the girls said it tasted just the same.  This lead to a really fun discussion about how the Peep must have air inside it to be so light and when the air around it got sucked away and became low pressure the air inside the Peep expanded making the Peep get bigger.  When we let air back into the mason jar then the Peep went back to its original size as the outside air moved back into the mason jar and made the air pressure higher.  

Peep Experiment 2:  What happens to a Peep in water? {or solubility testing}

Now our Peep seemed pretty resilient to being blown up and shrunk back down when we changed the air pressure so we wanted to know what would happen to a Peep in water.  The girls thought he would float on the water because he had air in him.

Well he must really be a duckling because this little Peep floated in tap water.  We did however notice that the water did begin to change color.  So then we wondered what would happen to our Peep if we put him in ice water.

Well he floated too!  The girls were concerned that the ice was keeping the Peep up.  So we watched and waited and the Peep kept on floating.  So then we decided to test the Peep in boiling water.  I was very careful to explain to them not to touch our mason jar of boiling water and Bug very carefully dropped the Peep into the boiling water.  This peep floated as well ...

... but immediately began to fizz and melt.  The girls thought this was really fun and took turns putting their ears near the Peep to hear the fizzing bubbles.  We continued to watch and wait and over the next 10 minutes we noticed our Peeps were changing:

Our Peep in hot water (top) was becoming a white blob (which later completely disappeared/dissolved).  The other two Peeps were looking a little different too.  So I invited the girls to feel the Peeps.  We just dipped our finger into the hot water Peep which felt like a light foam.  The other two Peeps felt a bit slimy on the outside but the ice water one felt a little firmer than the one in tap water.

The girls loved observing the differences in the Peeps in the different water conditions.  They especially loved feeling the Peeps and the hot water Peep was quite the effect!  So then we wanted to know a bit more about how temperature affected the Peeps which brings us to experiment 3:

Peep Experiment 3:  How does temperature affect Peeps? {or structural integrity}

We could feel that there was a difference in the Peeps when we put them in different temperature water but now we wanted to know if we could see this change in another way - in particular how would a Peep stand up to being hit by a hammer.  Does temperature change a Peeps structural integrity?  So we put our Peeps in three different temperature conditions:  in a freezer on ice, room temperature, and in a 350 degree oven.

We put the Peep in the freezer first while we set everything else up including waiting for the toaster oven to heat up.  I got a big cutting board as our work area and wrapped our hammer in cling wrap (as I was anticipating some stickiness).  After a few minutes in the oven the Peep was looking well roasted and ready to come out.   We brought the oven and freezer Peeps out and started by observing any differences.

The first thing the girls noticed was that the oven Peep was missing his eyes.   After looking a bit more we noticed that the oven Peep was the biggest and the freezer Peep was the smallest (left).  I asked the girls which one would smoosh (official Peep lack of structural integrity term) the most when we hit it with a hammer.  The girls thought the oven/hot Peep.  The hot Peep did indeed "smoosh" when we hit it.

I did not hit very hard but the Peep did not hold its shape at all.   Then we tested the cold Peep (from the freezer).  He did not change very much and when we lifted the hammer it almost returned to his original shape.  

Finally we tested the room temperature peep which became more compacted than the cold Peep.

There was definitely a change in how well the Peeps could stand up to a force when you changed the temperature of the peep.   The hot Peep had started to melt so it did not do a good job of standing up to the hammer.  The cold Peep felt harder and showed that it was good at resisting the hammer.  Of course the best part was eating the leftovers!

We hope you will have as much fun with these Peeps experiments as we did.


  • Peeps (we used 7 in total and ate a few more)
  • Exp 1:
    • Vaccum sealer with canning attachment
    • Mason jar
  • Exp 2:
    • Mason jar with tap water
    • Mason jar with boiling water
    • Mason jar with ice water
  • Exp 3:
    • Oven
    • Freezer
    • Hammer wrapped in cling wrap
    • Large cutting board


  1. Exp 1:
    1. Connect the canning attachment to the vacuum sealer.
    2. Place a peep in a mason jar.
    3. Place the attachment on the jar and "seal" the jar.
    4. Watch the Peep change as the jar is vacuumed.
    5. Release and observe the Peep change again.
  2. Exp 2: 
    1. Place a Peep in each of the mason jars of water.
    2. Watch what happens to the Peeps for a few minutes.
    3. Check every 5 minutes for about 20 minutes to observe and feel the changes in the Peeps.
  3. Exp 3:
    1. Place a Peep in the freezer.
    2. Wrap the end of a hammer in plastic wrap.
    3. Heat an oven to 350 degrees and place a Peep in the oven for a few minutes (until looking toasted)
    4. Take the Peep out of the oven and the freezer and place next to the room temperature Peep.
    5. Hit each Peep with a hammer to see how it changes.  {you may need to change your plastic wrap after hitting the hot Peep}


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