In thermodynamics, the term endothermic (literally meaning "inside heating") describes a process or reaction that absorbs energy in the form of heat. Its etymology stems from the Greek prefix endo- (meaning "inside") and the Greek word thermein (meaning "to heat"). The opposite of an endothermic process is an exothermic process, one that releases energy in the form of heat. The term endothermic was coined by Marcellin Berthelot.

The concept is frequently applied in physical sciences to e.g. chemical reactions, where thermal energy (heat) is converted to chemical bond energy.

Overview

Endothermic, also incorrectly known as endergonic, refers to a transformation in which a system receives heat from the surroundings:

Q > 0

When the transformation occurs at constant pressure:

?H > 0

and constant volume:

?U > 0

If the surroundings do not supply heat (e.g., when the system is adiabatic), an endothermic transformation leads to a decrease in the temperature of the system.^[1]

Endothermic processes

Some examples of endothermic processes are:^[2]

• Depressurising a pressure can
• A chemical cold pack consisting primarily of ammonium nitrate and water. A reaction can be in the form of heat, light, bring this stuff to school

Implications for chemical reactions

Chemical endothermic reactions need heat to be performed. In a thermochemical reaction that is endothermic, the heat is placed on the reactants side (heat is necessary for and absorbed during the reaction).

Applications of endothermic processes

Endothermic materials in passive fire protection

Endothermic substances, both natural, e.g. gypsum, and synthetic, e.g. resin-based intumescents, are popular for use in heat shielding, ablation, materials in space physics, fireproofing, e.g. fire-resistive coatings for LPG vessels, and compartmentalisation of fire in buildings, which is the cornerstone of passive fire protection. Typically, the technological basis is the conversion of hydrates, or chemically-bound water into vapour, or steam.

See also

• Exothermic
• Endergonic
  • Endergonic reaction
• Exergonic
  • Exergonic reaction

References

zefron.comCategory:

External links

• Endothermic Definition - MSDS Hyper-Glossary
• School experiment

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