100 Day of Science #73 & 74-- Making a Marshmallow Sink & Grow

I have had a few fun marshmallow themed science experiments on my mind for months now and I finally sat the boys down to try them out.  We are finally closing in on our 100 Days of Science challenge and we are determined to finish it up soon. 

First I challenged them to see if they make a marshmallow sink.  We talked about why they float and how we could change or modify those physical properties.  

They tried breaking them into smaller pieces, making a hole through them, Alec carved out a cavity in his large marshmallow hoping it would fill with water and sink.

They tried holding them under water to see if they could saturate them, they tried sticking them to the sides of the glasses, and finally began flattening them.

I gave each of the boys a small piece of tin foil and a layer of cornstarch (the cornstarch just keeps the marshmallows from sticking to fingers while flattening them).  They began flattening their marshmallows as much as they could and testing it.. which makes the water a bit cloudy.

But eventually they all got their small marshmallows to sink (we could have made the larger ones sink too but it would have taken so much longer to make them completely flat).

Next up I challenged them to make a marshmallow grow.  They began talking about the different things that might work and before we even tried anything they all agreed heating the marshmallow was the best way to make it bigger.

We put two of them on a plate and stuck them in the microwave.

In just a few seconds we could already see them doubling in size!

We talked about how the heat makes the air molecules inside expand and therefor the whole thing expands.  We kept adding time just a few seconds at a time until they were not getting any larger (no more than 30 seconds total).

Then we took them out and watched to see if they would deflate and how quickly that might happen.

But, of course, the best part of the lesson was getting to eat the melted gooey mess in the end.

Others in this series:
53. Iodine and Starch Experiment
54. Flouride and Calcium Experiment
55. Botanical Gardens in Winter
56.  Making Cell Models
57. Which Has More Water; Ice or Snow?
58. Exploding Snow and Water Baggies
59.  Exploring Minerals
60. Visiting the Hartford Science Museum
61-63. 3 STEM Bridge Challenges
64. Making Models of the Earth
65. Plate Techtonics with Graham Crackers
66.  Homemade Lava Lamp
67.  Science Movies We're Watching
Index Card Towers

69.  Botany at the Botanical Gardens
70. Best Board Games for Science 
71. Homemade Frozen Yogurt Pops
72.  Starburst Rock Cycle 


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