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Photosynthesis, the process that allows plants to convert carbon dioxide and water to sugar and oxygen, is an endothermic process: plants absorb radiant energy from the sun and use it in an endothermic, otherwise non-spontaneous process. The chemical energy stored can be freed by the inverse (spontaneous) process: combustion of sugar, which ...
In thermochemistry, an exothermic reaction is a "reaction for which the overall standard enthalpy change ΔH⚬ is negative." [ 1 ] [ 2 ] Exothermic reactions usually release heat . The term is often confused with exergonic reaction , which IUPAC defines as "... a reaction for which the overall standard Gibbs energy change Δ G ⚬ is negative."
Freezing is almost always an exothermic process, meaning that as liquid changes into solid, heat and pressure are released. This is often seen as counter-intuitive, since the temperature of the material does not rise during freezing, except if the liquid were supercooled .
A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. [1] When chemical reactions occur, the atoms are rearranged and the reaction is accompanied by an energy change as new products are generated.
The reaction of molybdenum dioxide with the transporting agent iodine is an exothermic process, thus the MoO 2 migrates from the cooler end (700 °C) to the hotter end (900 °C): MoO 2 + I 2 ⇌ MoO 2 I 2 ΔH rxn < 0 (exothermic) Using 10 milligrams of iodine for 4 grams of the solid, the process requires several days.
The reaction is usually endothermic as heat is required to break chemical bonds in the compound undergoing decomposition. If decomposition is sufficiently exothermic, a positive feedback loop is created producing thermal runaway and possibly an explosion or other chemical reaction. Thermal decomposition is a chemical reaction where heat is a ...
An endothermic process may be a chemical process, such as dissolving ammonium nitrate (NH 4 NO 3) in water (H 2 O), or a physical process, such as the melting of ice cubes. [5] The opposite of an endothermic process is an exothermic process, one that releases or "gives out" energy, usually in the form of heat and sometimes as electrical energy. [1]
Endothermic reactions absorb heat, while exothermic reactions release heat. Thermochemistry coalesces the concepts of thermodynamics with the concept of energy in the form of chemical bonds. The subject commonly includes calculations of such quantities as heat capacity, heat of combustion, heat of formation, enthalpy, entropy, and free energy.