The Science of S'mores

Did you know that August 10 was National S’mores Day? Don’t worry if you missed it; it’s not exactly a well-known holiday. To help you celebrate (slightly belatedly), Science World investigates what it takes to transform chocolate, graham crackers, and marshmallows into the sweet goodness of s’mores.

Did you know that August 10 was National S’mores Day? Don’t worry if you missed it. It’s really not a well-known holiday. But we’re helping you celebrate (a little late). Science World looks at what it takes to change chocolate, graham crackers, and marshmallows into the sweet goodness of s’mores.

The first step to making a s’more is to make a fire (see On Fire). “Combustion is a chemical reaction,” says Sally Mitchell, a teacher in Syracuse, New York, and an expert for the American Chemical Society. During a chemical reaction, new substances are formed. Next, toast the marshmallow.

A marshmallow is mostly sugar whipped with air to make it fluffy. The treat also contains a stretchy molecule called gelatin that gives a marshmallow its structure. Gelatin is made up of proteins. These large molecules are essential to all living things. Heat from a campfire causes the sugar and proteins in a marshmallow to chemically react and form new substances—the brown crust you see on the outside of a toasted marshmallow.

The first step to making a s’more is simple. Toast a marshmallow over an open flame (see On Fire). “Combustion is a chemical reaction,” says Sally Mitchell. She’s a chemistry teacher in Syracuse, New York, and an expert for the American Chemical Society. New substances form during a chemical reaction.

A marshmallow is mostly sugar. It’s whipped with air to make it fluffy. The treat also contains a stretchy molecule called gelatin. This gives a marshmallow its form. Gelatin is made up of proteins. These large molecules are important to all living things. A campfire’s heat causes the sugar and proteins in a marshmallow to chemically react. They form new substances. One of these is the brown crust on the outside of a toasted marshmallow.

Once toasted, the marshmallow and a square of chocolate are sandwiched between two graham crackers. The hot marshmallow melts the chocolate. “It changes phases from a solid to a liquid,” says Mitchell. “This is a physical change because the chocolate’s components remain the same.” 

The sticky chocolate and marshmallow hold a s’more together. The graham crackers play an important role too—they keep your fingers from getting too messy as you munch the sweet treat.

The toasted marshmallow and a square of chocolate are placed between two graham crackers. The hot marshmallow melts the chocolate. “It changes phases from a solid to a liquid,” says Mitchell. “This is a physical change because the chocolate’s components remain the same.”

The sticky chocolate and marshmallow hold a s’more together. The graham crackers play an important role too. They keep your fingers from getting too messy as you munch the sweet treat.