Heat is a form of energy that can be transferred between objects or systems due to temperature differences. It is the energy transfer that occurs when there is a temperature gradient between two objects or within an object.
When the amount of heat in an object changes, it usually affects its temperature. If heat is added to an object, its temperature generally increases. This is because the added heat energy causes the particles within the object to move faster, which leads to an increase in the average kinetic energy of the particles and, consequently, an increase in temperature.
Conversely, if heat is removed from an object, its temperature typically decreases. The removal of heat energy causes the particles within the object to slow down, resulting in a decrease in the average kinetic energy of the particles and a subsequent decrease in temperature.
The change in the amount of heat in an object is primarily caused by thermal interactions between the object and its surroundings. Heat can be transferred through three main mechanisms: conduction, convection, and radiation.
Conduction: Heat transfer occurs through direct contact between objects or particles. Energy is transferred from the hotter object to the cooler object as the particles collide and transfer kinetic energy.
Convection: Heat transfer happens through the movement of a fluid (liquid or gas). The hotter fluid rises, creating a convection current, while the cooler fluid descends, creating a continuous transfer of heat.
Radiation: Heat is transferred through electromagnetic waves. This mechanism does not require a medium and can occur in a vacuum. The hotter object emits electromagnetic waves (thermal radiation), which can be absorbed by cooler objects, causing an increase in their heat energy.
Overall, the change in the amount of heat in an object is a result of energy transfer caused by temperature differences and the mechanisms of conduction, convection, and radiation.