Term: Exothermic process
– Two types of chemical reactions:
– Exothermic and endothermic describe two types of chemical reactions or systems found in nature.
– Exothermic:
– In exothermic chemical reactions, heat released takes the form of electromagnetic or kinetic energy.
– Electrons transitioning between energy levels release light equivalent to bond energy.
– Light released can be absorbed by other molecules, leading to molecular translations and rotations.
– Activation energy is less than the subsequent released energy, resulting in a net energy release.
– Exothermic reactions are generally more spontaneous compared to endothermic reactions.
– Endothermic:
– In an endothermic reaction or system, energy is absorbed from the surroundings.
– Examples include first aid cold packs and photosynthesis in plants.
– Photosynthesis absorbs radiant energy from the sun for an endothermic process.
– Energy stored in plants can be released through combustion of sugar.
– Endothermic reactions are driven by a favorable entropy increase in the system.
– Energy release:
– Exothermic reactions release energy to the surroundings in a closed system.
– Heat in exothermic reactions is equivalent to enthalpy change at constant pressure.
– At constant volume, heat equals internal energy change.
– Adiabatic systems show increased temperature during exothermic processes.
– Heat released in exothermic reactions can result in molecular translations and rotations.
– Examples:
– Exothermic thermite reactions release sparks and molten iron.
– Exothermic reactions are more spontaneous compared to endothermic ones.
– Heat may be listed among the products in exothermic thermochemical reactions.
In thermodynamics, an exothermic process (from Ancient Greek έξω (éxō) 'outward', and θερμικός (thermikós) 'thermal') is a thermodynamic process or reaction that releases energy from the system to its surroundings, usually in the form of heat, but also in a form of light (e.g. a spark, flame, or flash), electricity (e.g. a battery), or sound (e.g. explosion heard when burning hydrogen). The term exothermic was first coined by 19th-century French chemist Marcellin Berthelot.
The opposite of an exothermic process is an endothermic process, one that absorbs energy usually in the form of heat. The concept is frequently applied in the physical sciences to chemical reactions where chemical bond energy is converted to thermal energy (heat).