Which Phase Changes Are Endothermic

Thermodynamic process that absorbs energy from its surroundings

In thermochemistry, an endothermic process (from Greek ἔνδον (endon) 'within', and θερμ- (therm) 'hot, warm') is whatever thermodynamic process with an increase in the enthalpy $H$ (or internal energy $U$ ) of the system.^[1] In such a procedure, a closed organisation usually absorbs thermal free energy from its surroundings, which is heat transfer into the system. Thus, an endothermic reaction generally leads to an increase in the temperature of the organisation and a subtract in that of the surroundings. It may be a chemical process, such equally dissolving ammonium nitrate (NH_fourNO_iii ) in water (H_twoO), or a physical process, such equally the melting of ice cubes.

The term was coined by 19th-century French chemist Marcellin Berthelot. The opposite of an endothermic process is an exothermic process, i that releases or "gives out" free energy, usually in the form of heat and sometimes as electrical energy. Thus in each term (endothermic and exothermic) the prefix refers to where oestrus (or electrical energy) goes as the process occurs.

In chemistry [edit]

Due to bonds breaking and forming during various processes (changes in state, chemic reactions), there is usually a alter in free energy. If the energy of the forming bonds is greater than the energy of the breaking bonds, then energy is released. This is known as an exothermic reaction. However, if more energy is needed to break the bonds than the energy being released, energy is taken upward. Therefore, it is an endothermic reaction.^[ii]

Details [edit]

Whether a process can occur spontaneously depends not only on the enthalpy modify but likewise on the entropy modify ( $∆ S$ ) and accented temperature $T$ . If a procedure is a spontaneous process at a certain temperature, the products accept a lower Gibbs free free energy $G = H - TS$ than the reactants (an exergonic process),^[1] even if the enthalpy of the products is higher. Thus, an endothermic process usually requires a favorable entropy increase ( $∆ South > 0$ ) in the system that overcomes the unfavorable increment in enthalpy so that still $∆ G < 0$ . While endothermic phase transitions into more disordered states of higher entropy, east.one thousand. melting and vaporization, are common, spontaneous chemic processes at moderate temperatures are rarely endothermic. The enthalpy increase $∆ H ≫ 0$ in a hypothetical strongly endothermic process usually results in $∆ Chiliad = ∆ H - T ∆ Due south > 0$ , which means that the process will not occur (unless driven by electric or photon energy). An example of an endothermic and exergonic process is

{\ce {C6H12O6 + 6 H2O -> 12 H2 + 6 CO2}}

\Delta _{r}H^{\circ }=+627\ {\text{kJ/mol}},\quad \Delta _{r}G^{\circ }=-31\ {\text{kJ/mol}}

Examples [edit]

Evaporation
Sublimation
Slap-up of alkanes
Thermal decomposition
Hydrolysis
Nucleosynthesis of elements heavier than nickel in stellar cores
High-energy neutrons can produce tritium from lithium-vii in an endothermic process, consuming 2.466 MeV. This was discovered when the 1954 Castle Bravo nuclear test produced an unexpectedly high yield.^[3]
Nuclear fusion of elements heavier than iron in supernovae ^[4]
Dissolving together barium hydroxide and ammonium chloride
Dissolving together citric acid and baking soda^[v]

Distinction betwixt endothermic and endotherm [edit]

The terms "endothermic" and "endotherm" are both derived from Greek ἔνδον endon "within" and θέρμη thermē "heat", merely depending on context, they can accept very different meanings.

In physics, thermodynamics applies to processes involving a system and its surroundings, and the term "endothermic" is used to draw a reaction where energy is taken "(with)in" past the organization (vs. an "exothermic" reaction, which releases energy "outwards").

In biology, thermoregulation is the ability of an organism to maintain its trunk temperature, and the term "endotherm" refers to an organism that can do and then from "within" by using the heat released by its internal bodily functions (vs. an "ectotherm", which relies on external, environmental heat sources) to maintain an adequate temperature.

References [edit]

^ ^a ^b Oxtoby, D. W; Gillis, H.P., Butler, L. J. (2015).Principle of Modernistic Chemistry, Brooks Cole. p. 617. ISBN 978-1305079113
^ "Exothermic & Endothermic Reactions | Energy Foundations for High School Chemistry". highschoolenergy.acs.org . Retrieved 2021-04-xi .
^ Austin, Patrick (Jan 1996). "Tritium: The ecology, health, budgetary, and strategic effects of the Section of Energy's determination to produce tritium". Institute for Energy and Environmental Enquiry. Retrieved 2010-09-15 .
^ Qian, Y.-Z.; Vogel, P.; Wasserburg, G. J. (1998). "Diverse Supernova Sources for the r-Process". Astrophysical Journal 494 (1): 285–296. arXiv:astro-ph/9706120. Bibcode:1998ApJ...494..285Q. doi:10.1086/305198.
^ "Messing with Mass". WGBH. 2005. Retrieved 2020-05-28 .

External links [edit]

Endothermic Definition – MSDS Hyper-Glossary