Praxis: An expanding and smiling marshmallow

By Medicine Hat News on April 7, 2018.

Well it looks like we may be stuck inside this weekend, again. I know it’s spring and we all want to get outside. All I can say is to be patient; spring will be here before you know it. In the meantime, there are plenty of science activities that can keep you busy inside. This week, I thought we could use up some of those Easter treats that may be lying around. Let’s get started!

*Remember to ask an adult before you do this experiment.

Materials

– clear glass

– marshmallow

– food colouring

– plasticine

– straw

– plate

– cotton swab

– standing mirror or one on the wall you can work in front of

Procedure

1. Set all of your materials up in front of a mirror. If you have one that stands freely on its own, that is great. Place it on a flat surface to work on. You have to be able to see the jar in the mirror as you are doing this experiment.

2. Put a few drops of food colouring onto the plate.

3. Using the cotton swab, draw a funny face on the marshmallow.

4. Place the marshmallow in the clear glass.

5. Seal the top of the glass with some plasticine.

6. Stick the straw through the middle of the plastic, and seal all around it so that it can stand up freely. Note: you do not want the straw to touch the bottom of the glass or the marshmallow — just above the marshmallow will work great.

7. Using the straw, suck as much air as you can out of the glass. While you are doing this, watch your marshmallow face in the mirror.

8. Stop sucking and watch the marshmallow face this time.

What is going on?

You should have seen the marshmallow grow as you suck the air out of the glass. When you stop sucking, the marshmallow will actually deflate. Air is a tricky substance because you cannot see it. The air around us spreads out and fill whatever space(s) are available. All of those molecules start bumping into one another to find somewhere to go. In this case, due to there being no air in the glass, the air in the marshmallow began to push out, pushing the marshmallow sides and making it grow right before your eyes. Once you stop sucking the air, it rushes back into the glass, and as a result, squishes the marshmallow as it is looking for somewhere to go!

Patty Rooks is senior scientific consultant at PRAXIS, “Connecting Science To The Community.” Contact Praxis at praxis@praxismh.ca, http://www.praxismh.ca, Tweet or follow us @PraxisMedHat, or friend us on Facebook.