FROZEN FLAVOR

Sweat drips down your face. It’s a scorching summer day. You need something cold to beat the heat. What do you reach for? An ice pop! The frozen treat glistens in the sun. You take a lick. Ahh! That’s better

Ice pops have helped people cool down for decades. The first one is said to have been made in 1905 by Frank Epperson. The 11-year-old lived in the San Francisco Bay Area, in California. He left a cup of soda outside overnight with a stick in it. When he woke up the next day, the soda had frozen solid. That night changed his life. It inspired Epperson to start the now-famous Popsicle brand.

But what exactly happened to turn the liquid soda into a solid pop? Science Spin asked a scientist to find out.

The first-ever ice pop was made possible thanks to chilly night air. If Epperson had left out his soda on a warmer night, we might not have ice pops today!

“Cold temperatures cause molecules to lose energy,” says Katerina Roth. She’s a food scientist at Cornell University in New York. Molecules in a liquid pack tightly together when they lose energy. That’s what happens when a liquid gets cold enough to freeze into a solid.

Pops don’t freeze all at once. They freeze from the outside toward the center. The middle might be slushy if it’s removed from the cold too soon.

The opposite happens when you eat your frozen treat. An ice pop melts as you lick it with your warm tongue. “Warmth adds energy to the ice pop’s surface,” says Roth. “It causes the solid to turn back into a liquid, which can make a mess as it drips!

You can test out this food science—and make delicious ice pops—at home. Start with a liquid base, like fruit juice.

Next, pour the liquid into a mold and keep it at a cold temperature. Your freezer is cold enough to turn your liquid into a solid. Water freezes at 32°F. But different liquids become solids at different freezing points.

Juice has a lower freezing point than water. That’s due to the sugar in the juice. Because of this, your freezer will need to be colder than 32°F to freeze your treat completely solid. It’s a good idea to freeze your pops overnight so you don’t get a slushy surprise. Now enjoy on a hot summer day—or anytime!