What is heat? It is a force that makes objects expand and contract to a certain temperature. Heat energy can be classified as being stored or available in some kind of molecules. Some examples of the many kinds of molecules are air, rock, coal, and water.
Heat is often associated with physical energy. Heat energy comes from the motion of small particles within all matter. When those particles move faster, the amount of available thermal energy increases tremendously. Temperature is normally measured in Fahrenheit, degrees Celsius, or with the Krell scale.
In the context of what is heat, different types of materials have different properties. Some materials are made up of little droplets of fluid, while other materials are composed of little rock grains. Some kinds of liquids, like water, have a much higher density than do other liquids. Since heat moves slower at lower temperatures, hot liquid droplets have a much shorter distance to travel to the cooler ambient temperatures, allowing heat to be stored more easily in them.
One way to think about heat transfer, then, is as a process in which energy is changed from a colder to warmer medium. The fluid goes from cool to warm, and then the change causes a corresponding change in temperature. One example of such a process may be the rising of an ice cube in a pot of water. As the cube rises, it expands, taking heat from the water and transferring it to the ice. Another example includes changes in the volume of an oil droplet.
All kinds of solids, including ice, water, rock, and mud, are composed of molecules that move about. At low temperatures, atoms move very quickly; therefore, they do not retain heat well. As the temperature rises, however, the atomic molecules expand, taking longer to change state from cold to hot. This results in a change in temperature, known as convection, which is the heating of a fluid by its proximity to another fluid at a specific temperature. It is a rather complicated process, but one that can be studied using simple mechanical devices called convection cells. A convection cell contains a pump that sends a stream of fluid through a gap in the top plate.
Convection occurs for various reasons, including absorption and expelling of energy, changes in temperature and humidity, and conductive heat transfer conduction. In its simplest form, heat transfer conduction involves the transfer of energy from a point in a medium to a point in a cold medium. The concept is simple enough. If you take an example of a person walking on the ground, they would feel the difference in temperature between their toes as the air passes over their feet. The same thing goes for heat that is transferred from a hot surface to a cold surface. A convection cell contains one plate that is insulated from the cold, so that the heat is transferred to a second plate, usually on the inside of a closed box.
The convection process takes place because of some specific laws that govern the way that objects with different temperatures move relative to one another. These laws tell us what objects have a definite temperature that can be changed or transferred to and from each other. Because of these laws, you can easily understand why, for example, hot objects such as a frying pan will feel cold to the touch while colder objects such as a bed sheet or refrigerator door won’t.
What is heat then, really is radiation. When radiation is incident on an object, it changes its temperature instantaneously. The change is usually measured in joules and refers to the amount of heat per unit volume. When objects are moved by the heat, there is an equal amount of heat being transferred from them to the surroundings. If you want to get a clearer understanding of this concept, you should watch a science lesson about heat transfer or try to read a text on the topic.