Heat and heat energy are terms we use to describe the level of activity for the molecules in an object. An object with molecules that are very "excited" and move around rapidly is known as being hot, while an object with molecules whose atoms move around less rapidly is known as cold. The heat energy, or thermal energy, can be transferred between objects. So, heat refers to this energy transfer between objects, while temperature refers to the energy contained within the objects.
There are three basic ways to transfer heat energy: convection, conduction, and radiation. Convection transfers heat energy through gases or liquids. Conduction transfers heat energy from one solid to another. Radiation transfers heat in the form of waves or particles through places where there are no molecules. It is a form of electromagnetic energy. Here are some common examples of heat energy.
- The biggest example of heat energy in our solar system is the sun itself. The sun radiates heat to warm us up on the planet earth.
- When the burner of a stovetop is very hot, it is a source of heat energy. Anything placed onto the stovetop and warmed, whether a pot of tea or a skillet for frying eggs, also become sources of heat energy.
- Automobile fuels such as gasoline are sources of heat energy, as is the hot engine of a racecar or a school bus.
- A toaster is turned on and turns a piece of bread into a piece of toast. This is due to the radiant heat energy of the toast, which draws moisture from the bread and makes it crispy.
- A hot cup of steaming cocoa contains heat energy.
- Any fire, from the smallest match, to the fireplace, to the biggest forest fire ever, contains heat energy – with even the smallest of fires potentially resulting in the massive amount of heat energy seen in a huge blaze.
- When ice is placed into a glass of water, the heat energy from the water eventually melts the ice, meaning the water itself is a source of heat energy.
- A radiator or heating system in a home provides radiant heat energy to warm a house during those long, cold winter months.
- Conventional ovens are sources of convection heat energy, causing the food placed into it to become hot and cook.
- Your body contains heat energy that can warm a cold glass of lemonade, melt the ice on the other side of a window, and make someone else warm when you hug them.
- Geothermal energy is a type of heat energy generated and stored beneath the surface of the Earth. This type of energy is used to heat homes and buildings.
- A huge amount of heat energy is stored in a bolt of lightning, which can strike and start a fire or cause an electrical outage.
- Heat energy is contained inside of a hot piece of pizza – if it doesn’t cool down, that heat energy has the potential to hurt the roof of a person’s mouth.
- When your computer is turned on, the components inside of it generate heat energy, which needs to be cooled with a small fan installed within the machine.
- A bathtub filled with hot water contains enough heat energy to warm a cold body back to a comfortable level on a frigid day.
- There is heat energy inside a cat that can be transferred to a person when the warm animal jumps up onto his or her lap.
So, heat energy comes from an object or substance whose molecules and atoms are moving faster due to a rise in temperature. Now you have seen lots of examples of heat energy, the next time your pet climbs into your lap, you can experience first-hand how heat energy works.
Read about how some objects can store potential energy, ready to be released in different ways.