Guidance: Monster Marshmallows
What do you need? .
• marshmallows •a paper plate •a microwave •tongs
What do you do?
1. Put two marshmallows on a paper plate. . Put the plate in the microwave. Set the timer for 1 minute (60 seconds) on high.
Teacher’s note: DON’T microwave a marshmallow for more than 2 minutes. It will just turn dark brown and make a sticky mess.
2. Choose a couple of observers to report out loud and ask them to stand and watch through the window of the microwave. After about 20 seconds, they should see the marshmallows start to puff up. They’ll grow to about four times their original size! ( This would make a greatr podcast if anyone s interested in making one)
3. When the microwave turns off, take the plate out and put it where they can be seen.
4. Teacher’s note: The marshmallows will be very hot do not allow pupils to touch them.
5. Wait a few seconds until they have cooled, then pull one marshmallow off with tongs. Is the marshmallow hollow inside? Is the inside the same colour as the outside? If you were to you eat it, would it be soft or crunchy?
6. Leave the other marshmallow on the plate and watch it for a minute. When it shrinks back down, you can pull it with your fingers and make it into whatever shape you want. It will stay in that shape and get hard and crunchy.
What is happening? .
Marshmallows are mostly sugar and water wrapped around a bunch of air bubbles. When you cook marshmallows in the microwave, the microwave makes the water molecules vibrate very quickly—which makes the water heat up. The hot water also warms the sugar, which softens a little. The hot water also warms the air bubbles.
When you warm air in a closed container, the gas molecules move around faster and push harder against the walls of the container. As the air in the bubbles warms up, the air molecules bounce around faster and faster and push harder against the bubble walls. Since the sugar walls are warm and soft, the bubbles expand, and the marshmallow puffs up. If it puffs up too much, some air bubbles burst, and the marshmallow deflates like a popped balloon.
When you take the marshmallow out of the microwave and it cools off, the bubbles shrink and the sugar hardens again. When the microwave marshmallow cools, it’s dry and crunchy. We think that’s because some of the water in the marshmallow evaporates when the marshmallow is hot.
If you cook your marshmallow for too long, it turns brown or black inside. That happens when the sugar gets so hot that it starts to burn.
Useless but interesting fact:
Ancient Egyptians made a puffy white treat out of honey and the dried, carrot-shaped root of the marsh mallow plant, which grows in fields and swamps. Today we still call these sweets marshmallows, but now they’re made with sugar and gelatine