In thermochemistry, latent heat is the amount of energy in the form of heat released or absorbed by a substance during a change of phase (i. In Thermodynamics and Physical chemistry, thermochemistry is the study of the Heat evolved or absorbed in Chemical reactions Thermochemistry In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός In Physics, heat, symbolized by Q, is Energy transferred from one body or system to another due to a difference in Temperature A state of matter (or physical state, or form of matter) has physical properties which are qualitatively different from other states of matter e. solid, liquid, or gas), – also called a phase transition. [1][2]
The term was introduced around 1750 by Joseph Black as derived from the Latin latere, to lie hidden. Year 1750 ( MDCCL) was a Common year starting on Thursday (link will display the full calendar of the Gregorian calendar (or a Joseph Black ( April 16, 1728 &ndash December 6, 1799) was a Scottish Physicist and Chemist, known for his The term is now dated, replaced by "enthalpy of transformation". In Thermodynamics and molecular chemistry, the enthalpy (denoted as H, h, or rarely as χ) is a quotient or description of
Two latent heats (or enthalpies) are typically described: latent heat of fusion (melting), and latent heat of vaporization (boiling). The standard Enthalpy of fusion (symbol \Delta{}H_{fus} also known as the heat of fusion or specific melting heat, is the amount of Melting is a process that results in the phase change of a substance from a Solid to a Liquid. The enthalpy of vaporization, (symbol \Delta{}_{v}H also known as the heat of vaporization or heat of evaporation, is the Energy required Boiling (also called ebullition) a type of Phase transition, is the rapid vaporization of a Liquid, which typically occurs when a liquid The names describe the direction of heat flow from one phase to the next: solid → liquid → gas.
The change is endothermic, i. In Thermodynamics, the word endothermic "within-heating" describes a process or reaction that absorbs Energy in the form of Heat. e. the system absorbs energy, when the change is from solid to liquid to gas. It is exothermic (the process releases energy) when it is in the opposite direction. In Thermodynamics, the word exothermic "outside heating" describes a process or reaction that releases Energy usually in the form of Heat, but For example, in the atmosphere, when a molecule of water evaporates from the surface of any body of water, energy is transported by the water molecule into a lower temperature air parcel that contains more water vapor than its surroundings. Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five Water is a common Chemical substance that is essential for the survival of all known forms of Life. An air parcel is an imaginary volume of air used by Meteorologists to conceptualize the Thermodynamic Fluid motions of the atmosphere for use General properties of water vapor Evaporation/sublimation Whenever a water molecule leaves a surface it is said to have evaporated Because energy is needed to overcome the molecular forces of attraction between water particles, the process of transition from a parcel of water to a parcel of vapor requires the input of energy causing a drop in temperature in its surroundings. If the water vapor condenses back to a liquid or solid phase onto a surface, the latent energy absorbed during evaporation is released as sensible heat onto the surface. In the Physical sciences a phase is a Set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties Sensible heat is Potential energy in the form of thermal energy or Heat. The large value of the enthalpy of condensation of water vapor is the reason that steam is a far more effective heating medium than boiling water, and is more hazardous.
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Latent heat equation
The equation for latent heat is:
where:
- Q is the amount of energy required to change the phase of the substance (in joules),
- m is the mass of the substance,
- L is the specific latent heat for a particular substance. The joule (written in lower case ˈdʒuːl or /ˈdʒaʊl/ (symbol J) is the SI unit of Energy measuring heat, Electricity
In other words, specific latent heat is found when energy is divided by mass.
Table of latent heats
| Substance | Latent Heat Fusion J/g |
Melting Point °C |
Latent Heat Vaporization J/g |
Boiling Point °C |
|---|---|---|---|---|
| Alcohol, ethyl | 108 | -114 | 855 | 78. 3 |
| Ammonia | 339 | -75 | 1369 | -33. Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor 34 |
| Carbon dioxide | 184 | -57 | 574 | -78 |
| Helium | 21 | -268. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical 93 | ||
| Hydrogen | 58 | -259 | 455 | -253 |
| Lead[3] | 24. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Characteristics Lead has a dull luster and is a dense, Ductile, very soft highly 5 | 372. 3 | 871 | 1750 |
| Nitrogen | 25. Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 7 | -210 | 200 | -196 |
| Oxygen | 13. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the 9 | -219 | 213 | -183 |
| R-134A | -101 | 215. 9 | -26. 6 | |
| Toluene | -93 | 351 | 110. Toluene, also known as methylbenzene or phenylmethane, is a clear water -insoluble liquid with the typical smell of Paint thinners redolent of 6 | |
| Turpentine | 293 | |||
| Water | 334 | 0 | 2260 | 100 |
References
- ^ Perrot, Pierre (1998). Turpentine (also called spirit of turpentine oil of turpentine wood turpentine gum turpentine is a fluid obtained by the Distillation of Resin obtained from trees Water is a common Chemical substance that is essential for the survival of all known forms of Life. A to Z of Thermodynamics. Oxford University Press. ISBN 0-19-856552-6.
- ^ Clark, John, O. E. (2004). The Essential Dictionary of Science. Barnes & Noble Books. ISBN 0-7607-4616-8.
- ^ Textbook: Young and Geller College Physics, 8e, Pearson Education
See also
The enthalpy of vaporization, (symbol \Delta{}_{v}H also known as the heat of vaporization or heat of evaporation, is the Energy required The standard Enthalpy of fusion (symbol \Delta{}H_{fus} also known as the heat of fusion or specific melting heat, is the amount of A Bowen ratio is the ratio of energy fluxes from one medium to another by sensible and latent heating respectively Sublimation of an element or compound is a transition from the Solid to Gas phase with no intermediate liquid stage Specific heat capacity, also known simply as specific heat, is the measure of the heat energy required to increase the Temperature of a unit quantityDapyx Software network: MP3 Explorer | Ebook Manager | Zenithic