The transfer of energy from one object to another occurs when there is a reaction, such as during a collision, according to the Chemical Education Digital Library. Different forms of energy, such as heat, light and motion, can be transmitted.
Thermal energy can be transferred by conduction, convection and radiation. When a person pushes another on the swings, they transfer their kinetic energy as seen when the person being pushed goes higher. Energy can be transmitted or converted, but it cannot be destroyed, according to the law of conservation of energy.
When energy is not being used, it is called potential energy. For instance, an immobile object located at some height above the ground has potential energy. If the object starts to fall, its potential energy is converted to motion or kinetic energy. The heavier and the higher the object is, the more potential energy it will have.
Transfer of thermal energy via conduction is aided by vigorously vibrating particles in a medium that has gained energy through heating. With convection, currents facilitate transfer of heat as warmer particles in a liquid move and their space is taken up by particles with less thermal energy. Infrared transfer of heat does not require a medium or particles. Heat from the sun reaches the Earth via radiation.