From the brains behind brains on, this is the Moment of Um.

Um, Um, um, um, um, um, um, um, um, um,

Moment of Um comes to you from APM Studios. I'm Frankie, and I'm a soup chef.

Um, I make soup. Sure I'll branch out to a stew or maybe a chowder if I'm feeling wild, but my specialty

is soup. And you know what most people don't realize? The temperature of your soup is almost as

important as the flavor. Take a nice gazpacho, for example. You want to serve that cold so it's

refreshing on a hot summer day.

On the other hand, a comforting bowl of chicken noodle has to be nice and warm, but not so hot that

it burns your tongue. It's a delicate balance. So when I make it a batch of soup, I always use

my trusty thermometer, not a digital thermometer. I like the kind that is like a glass stick

with some red liquid inside. Classic, like chicken noodle soup. Yesterday, I was testing the temp on a nice

big pot of potato leak soup when I realized, geez, I don't know how thermometers actually measure

temperature. My pal Reese was curious, too.

How do thermometers work? Thermometers are how we measure the heat energy of an object or its temperature.

My name is Nicholas Dranchi and I study experimental nuclear physics. A classic thermometer is a sealed glass tube that is filled with a liquid.

As you heat it up, the fluid expands, and as you cool it down, it contracts.

This is because if you zoom in really far, everything is made up of atoms.

These atoms are moving around really fast, when something is hot, so they push outwards.

When things are cold, they move slower, and the material contracts.

If you put a thermometer in a glass of hot water, the fluid inside the thermometer expands and rises.

You can then look to measure the temperature.

If you put a thermometer in a cold glass of water, the fluid inside of the thermometer shrinks and contracts.

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