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| {{About|states of matter|other meanings of heterogeneity, homogeneity, and related words|Homogeneity (disambiguation)|and|Heterogeneity (disambiguation)}}
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| [[File:The FireHouse Grill - Lunch.jpg|thumb|right|200px|[[Clam chowder]], a heterogeneous material]]
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| '''Homogeneity and heterogeneity''' are concepts relating to the uniformity in a substance. A material that is '''homogeneous''' is uniform in composition or character; one that is '''heterogeneous''' is distinctly nonuniform in one of these qualities.<ref name=websters-hetrogeneity>
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| Heterogeneous Mixtures, in chemistry, is where certain elements are unwillingly combined and, when given the option, will separates completely.
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| {{Cite web
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| | title =Webster's Revised Unabridged Dictionary (1913 + 1828)
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| | work =Heterogeneity
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| | publisher =The ARTFL Project, University of Chicago
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| | date =September 2010
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| |url =http://machaut.uchicago.edu/?resource=Webster%27s&word=Heterogeneity&use1913=on&use1828=on
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| | format =Part of this paragraph is public domain material copyright 1828 and 1913
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| | accessdate =2010-09-10}}</ref><ref name=Heterogeneous/><ref name=homogeneous-1913and1928/>
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| The words homogeneous and heterogeneous come from Medieval Latin homogeneus and heterogeneus, from Ancient Greek ὁμογενής (homogenēs) and ἑτερογενής (heterogenēs), from ὁμός (homos, “same”) and ἕτερος (heteros, “other, another, different”) respectively, followed by γένος (genos, “kind”), -ous is an adjectival suffix.
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| The concepts are the same to every level of complexity, from [[atom]]s to [[population]]s of [[animal]]s or [[Human|people]], and [[Galaxy|galaxies]]{{Clarify|date=September 2010}}. Hence, an element may be homogeneous on a larger scale, compared to being heterogeneous on a smaller scale. This is known as an [[effective medium approximations|effective medium]] approach, or effective medium approximations.<ref name=Gueguen>
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| {{Cite book
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| | last = Guéguen,
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| | first =Yves
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| | coauthors =and Palciauskas, Victor
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| | title =Introduction to the physics of rocks
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| | publisher =Princeton University Press
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| | date =May 1994
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| | pages = 53–72 (Chapter 3)
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| | url =http://books.google.com/?id=fCP5qyRyX-oC&pg=PA53&dq=heterogeneous+physics#v=onepage&q=heterogeneous%20physics&f=false
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| | format=
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| | isbn =978-0-691-03452-2}}Google Books preview download available</ref><ref name=Effective-medium>{{Cite journal| last = Shadrivov| first =Ilya V.| title =Nonlinear magnetic metamaterials|journal =Optics Express| volume =16| format =Introduction section. Free PDF download |pages =20266–71| date =2008-11-24| url =http://assets0.pubget.com/pdf/19065165.pdf
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| |doi =10.1364/OE.16.020266| accessdate =2009-11-26| pmid = 19065165| last2 = Kozyrev| first2 = AB| last3 = Van Der Weide| first3 = DW| last4 = Kivshar| first4 = YS| issue = 25|bibcode = 2008OExpr..1620266S }}</ref>
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| ==Heterogeneity==
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| '''Heterogeneity''' is the state of being '''heterogeneous'''. It is the nature of opposition, or contrariety of qualities. It is diverse in kind or nature; composed of diverse parts, or resulting from differing causes. In general, a heterogeneous entity is composed of dissimilar parts, hence the constituents are of a different kind. The parts (or constituents) are connected, and of a conglomerate mass, and viewed in respect to the parts of which it is made up.<ref name=Heterogeneous> | |
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| {{Cite web
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| | title =Webster's Revised Unabridged Dictionary (1913 + 1828)
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| | work =Heterogeneous
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| | publisher =The ARTFL Project, University of Chicago
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| | date =September 2010
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| |url =http://machaut.uchicago.edu/?action=search&word=heterogeneous&resource=Webster%27s&quicksearch=on
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| | format =Part of this paragraph is public domain material copyright 1828 and 1913
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| | accessdate =2010-09-10}}</ref><ref name=websters-heterogeneity>
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| Heterogeneous Mixtures, in chemistry, is where certain elements are unwillingly combined and, when given the option, will separate.
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| | |
| {{Cite web
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| | title =Webster's Revised Unabridged Dictionary (1913 + 1828)
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| | work =Heterogeneity
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| | publisher =The ARTFL Project, University of Chicago
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| | date =September 2010
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| |url =http://machaut.uchicago.edu/?resource=Webster%27s&word=Heterogeneity&use1913=on&use1828=on
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| | format =Part of this paragraph is public domain material copyright 1828 and 1913
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| | accessdate =2010-09-10}}</ref>
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| Various disciplines understand ''heterogeneity'', or being ''heterogeneous'', in different ways. For example:
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| *In [[physics]], it is understood as having more than one [[phase (matter)|phase]] (solid, liquid, gas) present in a system or process.{{Citation needed|date=September 2010}}
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| *In [[chemistry]], a heterogeneous material consists of either or both of a) multiple states of matter or b) [[hydrophilic]] and [[hydrophobic]] substances in one mixture; an example of the latter would be a mixture of water, [[octane]], and silicone grease.
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| *With [[information technology]] (see:[[Heterogeneous computing]]) it means a [[network science|network]] comprising different types of computers, potentially with vastly differing [[computer memory|memory]] sizes, processing power and even basic underlying architecture. Alternatively, a data resource with multiple types of formats.{{Citation needed|date=September 2010}}.
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| *In [[sociology]] it may refer to a society or group that includes individuals of differing ethnicities, cultural backgrounds, sexes, or ages.{{Citation needed|date=May 2011}}
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| *[[Rocks]] (geology) are inherently heterogeneous, usually occurring at the micro-scale and mini-scale.<ref name=Gueguen/>
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| *In [[medicine]] and [[genetics]], a [[genetic heterogeneity|genetic]] or [[allelic heterogeneity|allelic]] heterogeneous condition is one where the same disease or condition can be caused, or contributed to, by several factors. In the case of genetics, varying different [[gene]]s or [[allele]]s.
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| *In [[cancer research]], cancer cell heterogeneity is thought to be one of the underlying reasons that make treatment of [[cancer]] difficult.<ref>{{cite journal|last=Bhatia|first=Sangeeta|coauthors=John V Frangioni;Robert M Hoffman;A John Iafrate;Kornelia Polyak|title=The challenges posed by cancer heterogeneity|journal=Nature Biotechnology|date=10 July 2012|volume=30|pages=604–610|doi=10.1038/nbt.2294}}</ref>
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| ==Homogeneity==
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| {{main|Homogeneous (chemistry)}}
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| '''Homogeneity''' is the state of being '''homogeneous'''. Pertaining to the sciences, it is a substance where all the constituents are of the same nature; consisting of similar parts, or of elements of the like nature. For example, homogeneous particles, homogeneous elements, homogeneous principles, or homogeneous bodies; or (algebra) possessing the same number of factors of a given kind as with a [[homogeneous polynomial]].<ref name=homogeneous-1913and1928> | |
| {{Cite web
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| | title =Webster's Revised Unabridged Dictionary (1913 + 1828)
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| | work =Homogeneous
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| | publisher =The ARTFL Project, University of Chicago
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| | date =September 2010
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| |url =http://machaut.uchicago.edu/?resource=Webster%27s&word=homogeneous&use1913=on&use1828=on
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| | format =This is public domain material copyright 1828 and 1913
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| | accessdate =2010-09-10}}</ref>
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| ==Chemistry==
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| {{main|Homogenization (chemistry)}}
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| A heterogeneous mixture is a [[mixture]] of two or more [[Chemical compound|compounds]]. Examples are: mixtures of sand and water or sand and iron filings, a conglomerate rock, water and oil, a salad, [[trail mix]], and concrete (not cement).<ref>{{cite book|last=Gamow|first=George|title=One Two Three... Infinity|year=1967|publisher=Bantam|edition=Bantam Science and Mathematics, 5th printing|authorlink=George Gamow|accessdate=October 14, 2011|page=117|format=Mass market paperback|chapter=Chapter VI, "Descending Staircase"|month=April|quote=[Clam chowder] represents a nice example of what is known as a heterogeneous material.}}</ref> During the [[Sampling (statistics)|sampling]] of heterogeneous mixtures of particles, the variance of the [[sampling error]] is generally non-zero. [[Gy's sampling theory]] <ref>Gy, P (1979) ''Sampling of Particulate Materials: Theory and Practice'', Elsevier: Amsterdam, 431 pp.''</ref> quantitatively defines the '''heterogeneity''' of a particle as:
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| :<math>h_i = \frac{(c_i - c_\text{batch})m_i}{c_\text{batch} m_\text{aver}} .</math>
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| :<math>h_i</math>, the heterogeneity of the <math>i</math>th particle of the population
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| :<math>c_i</math>, the mass concentration of the property of interest in the <math>i</math>th particle of the population
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| :<math>c_\text{batch}</math>,the mass concentration of the property of interest in the population
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| :<math>m_i</math>, the mass of the <math>i</math>th particle in the population
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| :<math>m_\text{aver}</math>, the average mass of a particle in the population
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| '''Homogenization''' is the process of causing a heterogeneous mixture to become homogeneous, as is done with the making of [[homogenized milk]].
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| ===Homogeneous and heterogeneous reactions===
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| Homogeneous reactions are [[chemical reaction]]s in which the reactants are in the same [[phase (matter)|phase]], while heterogeneous reactions have [[reactant]]s in two or more phases. Reactions that take place on the surface of a catalyst of a different phase are also heterogeneous. A reaction between two gases, two liquids or two solids is homogeneous. A reaction between a gas and a liquid, a gas and a solid or a liquid and a solid is heterogeneous. {{Citation needed|date=September 2010}}
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| A mixture can be determined to be homogeneous when everything is settled and equal, and the liquid, gas, object is one color or the same form. Various models have been proposed to model the concentrations in different phases. The phenomena to be considered are mass rates and reaction rates.
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| == See also ==
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| * [[Complete spatial randomness]]
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| * [[Epidemiology]]
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| * [[Spatial analysis]]
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| * [[Statistical hypothesis testing]]
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| ==References==
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| {{Reflist}}
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| ==External links==
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| {{Wiktionary|homogeneity|heterogeneity|homogeneous|heterogeneous}}
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| *The following cited pages in this book cover the meaning of "homogeneity" across disciplines {{Cite book|last = Morris| first =Christopher G.|title = Academic Press Dictionary of Science and Technology
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| | publisher =Academic Press Inc.
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| | series =
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| | volume =
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| | edition =
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| | year =1992
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| | location =
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| | pages = 1039, 1040
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| | language =
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| | url =http://books.google.com/?id=nauWlPTBcjIC&pg=PA1039&dq=Homogeneity+in+physics#v=onepage&q=Homogeneity%20in%20physics&f=false
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| | isbn = 0-12-200400-0}}.
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| {{DEFAULTSORT:Homogeneous And Heterogeneous Reactions}}
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| [[Category:Chemical reactions]]
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| [[eu:Homogeneo eta heterogeneo]]
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