Do all frozen things feel equally cold? Melt your mind with this surprising sensory experiment.
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At least 4 hours before you want to do this experiment, place an ice cube in a zipper-lock bag, seal the bag (remove as much air as possible), and put the bag in the freezer. Place a 2-tablespoon piece of butter in a second zipper-lock bag, seal the bag (remove as much air as possible), and place that bag in the freezer, too.
Wait at least 4 hours to make sure the butter is fully frozen. While you’re waiting, make a prediction: When you take the ice cube and butter out of the freezer and hold them in your hands:
Whoa—that was weird, right? When we tried this experiment in the America’s Test Kitchen Kids lab, everyone agreed that the ice cube felt WAY colder than the frozen butter. But how can that be? The butter and the ice cube were in the same freezer, and when we measured their temperatures, they were both 3 degrees. What’s going on?
First things first: Things feel cold to us when heat is removed from our bodies. Heat always moves from warmer things (such as your hand, which is about 90 degrees) to colder things, such as the frozen butter or ice cube (which were about 0 degrees). The movement of heat energy out of your body is what makes you feel cold.
But why does the ice cube (frozen water) feel colder in your hand than the frozen butter?
It’s because water needs a LOT of heat energy to warm up. Butter, which is made of about 80 percent fat and only about 15 percent water, needs a much smaller amount of energy to warm up the same amount. Here’s one way to think about it . . .
Say you and a friend each have a bucket you want to fill up with water. Your bucket is a lot bigger than your friend’s bucket, so you need a lot more water (and time!) to fill it to the top. You’re like water! Your friend, who fills up their bucket quickly, with less water, is like butter.
To get water (or ice) hot, you need to fill up a big bucket with heat energy. To get the same amount of butter to the same hotness, you need to fill up only a small bucket with heat energy.
In our experiment, that heat energy comes from your nice warm hands. A lot of heat energy has to move from your hand to the ice to warm it up—that makes your hand feel very cold.
Warming the frozen butter takes a lot less heat energy, so a smaller amount of heat energy moves from your hand to the frozen butter, and your hand doesn’t feel quite as cold.
You can experience the same sensation in your mouth when you eat frozen desserts. (Now you have an excuse to eat frozen treats in the name of science!)
Frozen desserts with more fat in them, such as ice cream or gelato, will actually feel LESS cold in your mouth than frozen desserts with more water, such as sorbet or a slushie.
Give it a try! Invite some friends or family to participate in your tasting. Have your tasters close their eyes or wear blindfolds. Then have them taste a spoonful of ice cream or gelato, straight from the freezer, and then a spoonful of sorbet or slushie, also straight from the freezer. Ask them if one bite felt colder in their mouths than the other. Then, share what you learned!