Heat – you experience it everyday, and it is essential for life, but have you ever thought about where it comes from? In this lesson, find out what heat energy is and three ways it can be transferred.
Think about what your life would be like without heat. No more hot showers, hot food, or for that matter, no more warm sunlight to heat you up on a cold day! Imagine waking up in the morning and taking a cold shower, then eating a cold breakfast while sitting in your cold kitchen. Then getting in your cold car on a cold day, and heading to a cold school to sit in your cold classroom. What a crazy life that would be! Most of us take heat, a form of energy, for granted!Heat energy, also called thermal energy, is the energy an object has because of the movement of its molecules, and heat can be transferred from one object to another object.
Heat energy on Earth comes from the sun. Let’s take a look at how this happens.
How Heat Energy Works
Everything on Earth is made up of molecules. Molecules are so small, you would need a very powerful microscope to see them. Molecules are always moving, and just like us, the more excited they get, the more they move. Do you know what gets molecules excited? Heat! When molecules get excited, they touch other molecules, heating them up, and getting them excited, too.
This sharing of heat keeps spreading until all the molecules are the same temperature. Only then do they settle down.For example, think about putting butter on a warm, flaky biscuit. The molecules in the biscuit are warm and vibrating all around. When the butter is placed on the biscuits, the molecules in the biscuit begin to heat up and excite the molecules in the butter, and the butter starts to melt.
Heat energy is being transferred from the biscuit to the butter!
Ways to Transfer Heat Energy
Do you like popcorn? How do you like to pop it? Do you fix it in the microwave? Maybe you heat the popcorn up on the stove in a pan or use an air popper. Let’s think about popcorn popping to help us understand how heat is transferred. We will look at three ways that this transfer, or spreading of heat energy, can happen: radiation, conduction, and convection.
Heating through radiation, using a microwave, is truly the fastest and easiest way to pop popcorn! A microwave uses radiation, or waves, to heat things up. When you put a bag of popcorn in the microwave and press start, the microwave sends out heat waves.
These waves hit the popcorn kernels and get them excited, heating them up, and causing them to pop.
An example of conduction heating would be putting your popcorn in a pan and heating it on the stove. Conduction is the transfer of heat through solid objects. The molecules in the hot pan get excited and transfer their excitement and heat into the popcorn kernels that are lying in the pan.
Hence the solid pan is transferring its heat into the solid kernels through conduction.
When heat is transferred through gases or liquids, it is being transferred through convection. Heating popcorn using an air popper is an example of convection.
Here is how an air popper works. You put popcorn inside the machine and turn it on. The popper begins to blow very hot air into the machine, making the popcorn fly around inside of it.
As the popcorn is flying around, the hot air molecules are heating up the molecules in the popcorn, causing the popcorn to pop!
Remember, all objects are made up of molecules, and molecules always move. The more molecules move, the more heat energy they have. That energy can be transferred from one object to another through radiation, conduction, or convection.