Why Do Marshmallows Expand In The Microwave


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    Why Do Marshmallows Expand In The Microwave

    If you’ve ever put a marshmallow in the microwave, you’ve probably noticed that it expands to about twice its size. But why does this happen? It turns out that marshmallows are full of air, and when they’re heated, that air expands and causes the marshmallow to puff up. This process is called “thermal expansion,” and it’s the same reason why hot air balloons rise into the sky. So next time you’re making s’mores or just want a quick snack, remember that your marshmallows are expanding because of physics!

    What is marshmallow expansion?

    Marshmallows are made mostly of sugar, which is why they melt and expand in the microwave. The expansion is caused by the rapid heating of the sugar, which breaks down the structure of the marshmallow and allows it to “inflate” with steam.

    The science behind marshmallow expansion

    When you put a marshmallow in the microwave, the heat causes the water inside the marshmallow to expand. This expansion makes the marshmallow puff up and become bigger.

    The science behind this phenomenon is quite simple. When you heat water, it expands. This is because the molecules of water start moving around faster when they are heated. This movement takes up more space, causing the water to expand.

    Marshmallows are made mostly of water, so it makes sense that they would expand when heated. But why do they get so big?

    Well, it turns out that marshmallows are also full of air. And when you heat air, it also expands. So, when you put a marshmallow in the microwave, the heat makes both the water and the air inside expand, causing the marshmallow to puff up like a balloon!

    The history of the marshmallow

    Marshmallows have been around for centuries. The first recorded marshmallow recipe was found in France in 1660. In the early 1800s, candy was made from the root of the marshmallow plant. The modern marshmallow we know and love today was invented in the early 1900s.

    Marshmallows were originally only available to the wealthy. They were luxury items made from expensive ingredients like honey and sugar. It wasn’t until the mid-1900s that marshmallows became more affordable and accessible to everyone.

    Today, marshmallows are a popular treat enjoyed by people all over the world. They can be enjoyed on their own or used in recipes like s’mores or Rice Krispie treats.

    How to make your own microwaveable marshmallows

    If you’re looking for a fun and easy kitchen project, why not try making your own microwaveable marshmallows? All you need is a microwave-safe bowl and some basic ingredients.

    Start by heating up 1/2 cup of water in the microwave until it’s hot but not boiling. Then, add 1 teaspoon of gelatin and stir until it’s completely dissolved.

    Next, add 1/2 cup of sugar and 1/2 cup of light corn syrup to the bowl and stir until everything is combined. Microwave the mixture for 2-3 minutes, or until it starts to boil.

    Once the mixture is boiling, carefully pour it into a greased 9×13-inch baking dish and let it cool for at least an hour. Once it’s cooled, cut it into small squares and enjoy!


    This article has hopefully given you a better understanding of why marshmallows expand in the microwave. While it may not be the most exciting science experiment, it’s still pretty neat to see how microwaves can cause such a drastic change in such a small amount of time. So next time you’re feeling like making some s’mores, remember how those marshmallows got so big in the first place!


    One of the most curious phenomena in the kitchen is why marshmallows seem to expand when placed in the microwave. It can be a bit disconcerting to place a small puffy marshmallow into the microwave and then watch it magically transform into a larger, gooey version of its former self. But what is actually happening when you place marshmallows inside your microwave and press cook?

    The answer lies within the composition of a marshmallow. Marshmallows are made up of sugar, water, and gelatin that form an airy matrix. When microwaves pass through this matrix, they cause water molecules to vibrate which creates heat energy. This heats both the air pockets as well as syrup that is present between them, causing them to expand at different rates.

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