Temperature Definition: Lesson for Kids

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  • 0:04 Temperature
  • 2:07 The Importance of Temperature
  • 3:28 Lesson Summary
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Lesson Transcript
Instructor: Heather Jenkins

Heather has a bachelor's degree in elementary education and a master's degree in special education. She was a public school teacher and administrator for 11 years.

Whether it's a bite of hot soup, the cool waters of the ocean, or a fever when we are sick, temperature is a part of our everyday lives. In this lesson, you'll learn all about temperature.


When you choose an outfit for the day, you think about it. When you touch a pan with piping hot pizza rolls on it, you experience it. When it's high enough in your body, you're probably sick. So what is it?

Temperature is how much heat is in something, and you experience it every day. Another way to think of temperature is how hot or cold something is. Temperatures can range from freezing cold to stifling heat. Being able to measure and understand temperature is important to many things in our lives.

Temperature is measured by taking an average of the kinetic energy of a substance's molecules. This is simply the energy created by how fast the molecules move in a solid, liquid, or gas. Substances with more heat and higher temperatures have molecules that move faster and have a higher kinetic energy than those with less heat. As the molecules move faster and faster, they move farther apart. Just like marshmallows get bigger and spread apart when you roast them over a campfire, substances expand, or get bigger, as the molecules move faster and temperature increases.

Temperature can be measured numerically using a thermometer. A standard thermometer, like the one here, is a tube that's filled with a liquid, such as mercury. So, how do these moving molecules affect a thermometer?


As the temperature of the solid, liquid, or gas around the thermometer increases, the liquid in the thermometer also gets hotter. As the temperature of the liquid in the thermometer increases, the liquid begins to expand and move up the tube. The hotter the liquid in the thermometer becomes, the more it expands and moves up the tube. The level of the liquid in a thermometer is compared to the scale on the outside of the thermometer. Common thermometers usually measure temperature in degrees Fahrenheit or Celsius. Many times you will see this symbol, °, instead of the words 'degrees.' For example, 15°F, is read as 15 degrees Fahrenheit.

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