Energy is in essence the ability and power to perform tasks and do work. Thermal energy is this force that takes the form of heat. Heat is ostensibly the motion of molecules and atoms inside a substance. If the molecules and atoms vibrate rapidly inside a substance the hotter that substance will be and the greater the thermal energy produced and radiated by it would be. There is a close correlation between heat and temperature and if you increase the heat of a substance by applying energy, thereby causing the molecules and atoms inside the substance to travel or vibrate more rapidly you invariable increase the substance’s temperature. However, in the instance of water for example, once it reaches its boiling point you cannot raise its temperature further by increasing its thermal energy. In this case the water would be converted into steam in the process of evaporation.

The sun is the principal source of heat and its core is a mass of rapidly-moving gas particles. The sun’s radiated heat provides our planet with a very powerful stream of thermal, solar energy. Other forms of energy can also be transformed into thermal energy. For example, the burning of fossil fuels utilizes combustion to convert the stored solar energy in the fossil fuel (originally plants that absorbed sunlight in order to produce food) into thermal energy. We use thermal energy to generate electricity, heat our homes and enable steam-driven processes.

The uses of thermal energy require heat to be transferred from a hot substance to a cold substance, which increases the temperature of the cold substance and thereby results in a change of state – whether from solid to liquid, liquid to gas, etc. Heat transference happens chiefly by three methods, or by a combination of them. The first is conduction, where thermal energy is transferred through a solid substance or from one substance to another by means of transferring heat from one molecule to another, causing the molecules to get hotter thereby vibrating and colliding more frequently causing additional ones to become hotter and so on until the energy has sufficiently been dissipated into nearby molecules. Heat travels through a substance, and its value as a conductor is reliant upon its molecular structure.

Convection is the next process and in this process heat is transferred by the movement of hot particles. Convection occurs in liquids and gases, but not in solids as their particles are unable to move freely. Convected heat always travels to a colder place, and the hot particles that contain thermal energy are the ones that travel. As an example, convection heaters blow out hot air particles which then disperse into cooler air.

The final process is radiation, and the sun is a good example of this process. The sun’s radiated energy is able to travel across space due to the fact that it does not need any particles of matter – unlike the processes of conduction and convection. This kind of radiant energy travels in electromagnetic waves and these waves are divided according to wavelength. An example of the application of this kind of energy is in the use of infrared lamps used to ease muscular pain. These lamps produce thermal heat generated by electricity which is transferred by radiation to the body.

(Energy FAQ Series)

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