Talk:Chemical substance

message: I'm not sure this is really a disambiguation page. It's not so much that the term "chemical substance" is inherently ambiguous, merely that the term deliberately refers to a group of things, each of which has its own (comprehensive) article, and so an overarching article is unnecessary. It probably isn't necessary to disambiguate incoming links, because the term "chemical substance" is deliberately non-specific. So I'm proposing that the page be left as-is and merely the disambiguation notice be removed. Soo 00:57, 20 November 2005 (UTC)
replies: text: I support that. Soo has summed up the situation eloquently - when people make a link to chemical/chemicals/Chemical substance (which all redirect here) they don't know if it's an ion/compund/element they just want a general discussion. Remove the  tag.--Commander Keane 19:46, 20 November 2005 (UTC)
replies: text: Support.  I agree, this page clearly is not a dab page, it is only structured as a dab page.  It does need to be rewritten at some point and structured to be a regular article. Thaagenson 18:55, 28 November 2005 (UTC)
replies: text: Done,  removed.--Commander Keane 18:43, 30 November 2005 (UTC)

text: I tentatively accept that this page may not be so strictly a disambiguation page, but what is the reason for the total reorganization of its content into several sections that clutter the page? - Centrx 19:38, 15 May 2006 (UTC)
replies: text: Does Wikipedia cater only to professionals? Is there no room for an article that gives a reader a general idea of what a "chemical substance" might be without wading through 5 or 6 (or 10 or 12) other articles? Furthermore, based on the number of links to this article, some editors don't particularly care to distinguish what (if anything) they specifically mean by this term, either. Ewlyahoocom 10:58, 16 May 2006 (UTC)
replies: text: You're absolutely right, it just needs someone to write it - and writing "general" articles like this is always harder than it seems (something like sodium hydroxide is much easier).  Maybe this summer I'll have a go at writing this, though there are so many chem articles like this needing a lot of work.   Maybe you could nominate it for the next Chemistry Collaboration of the Month? Walkerma 15:13, 16 May 2006 (UTC)

text: I do not object to this, per se, but this is not accomplished by simply copying the first paragraph of all of the other articles, and the way it was done sent the article off the screen where before it fit compactly. - Centrx 00:33, 18 May 2006 (UTC)
thread_title: Is this a disambiguation page?

message: Yes, all this information can be found by following the link (although in some cases the article introductions are not good for a layman). However, the purpose of transforming the article is to provide a high-level overview of chemical substances in general. Otherwise, there would be no reason to state how many known elements there are, or even that elements are divided into metals and non-metals in the first place, or that compounds are divided into organic and inorganic, or that some have covalent bonding and some ionic. All of this information is found in the linked articles, but if the purpose is a general overview, it needs to be consistent, even, and not skip explanations. —Centrx→talk 23:18, 13 June 2006 (UTC)
replies: text: To understand what everything (including ourselves) is made of, and how things interact with one another. Walkerma 03:42, 29 September 2006 (UTC)
thread_title:  Explaining metal, bond, ion, etc. 

message: Should chemical compound and chemical substance be merged?--Smokefoot 13:26, 25 September 2006 (UTC)
replies: text: No, don't think so.  Sodium and certain alloys are chemical substances, but not chemical compounds.--Dirk Beetstra T C 14:00, 25 September 2006 (UTC)
replies: text: I wish we could, because there is so much overlap, but unfortunately "substance" is broader because it includes chemical elements.  If these were obscure terms it might be OK to merge and explain the differences on a single page, but in this case both pages probably get a lot of hits. Many high school students are unclear on these terms, so for the sake of clarity we should keep them separate. Walkerma 15:09, 25 September 2006 (UTC)
thread_title: Merge with chemical compound?

message: Upgraded it to Start. TerriG149.155.96.5 19:15, 27 October 2006 (UTC)
thread_title: Rating

message: I have problems with this recent edit:-
"A particular composition of a particular set of elements can be present in the form of several chemical organic compounds; this is so because of isomerism and tautomerism."
There is a clear difference, in the context of chemical substances.  If several isomers are present, there are several chemical substances. Tautomerism is when two isomers, of a kind, are in chemical equilibrium. Mostly a mix of isomers is not, by a long way, in equilibrium. Dimethyl ether and ethanol are isomers, but they are not in equilibrium. One is more stable, but either can exist, essentially for ever, as the barrier for interconversion is so high. Yes, it is a gradation, but like the difference between strong and weak acids there is a clear difference between isomers not in equilibrium and those that are. We call the latter tautomers. If they are in equilibrium we call it one chemical substance. If they are not in equilibrium we say they are different chemical substances. In the case of weak acids we say acetic acid is one chemical substance even though there are three species - acid, H cation and anion. In the case of strong acids we sometimes say there are two chemical substances - cation and anion - but I agree that sometimes we say there is just one substance. It depends on the context there. Nevertheless isomers and tautomers are quite different. --Bduke 12:38, 19 May 2007 (UTC)
replies: text:  I would like to add, isomers that are in equilibrium in a solution in a solvent cannot be called a single substance; so only if glacial acetic acid is cent percent pure it can be called a pure substance. I am not very sure if in absolutely pure acid there are independent hydrogen ionsHallenrm 02:33, 20 May 2007 (UTC)
replies: text: I think I disagree. Acetic acid in water is two chemical substances even though the acetic acid is in equilibrium with hydronium and acetate ions. Similarly if a ketone is mixed with water and there are keto and enol forms, we still say there are two chemical substances, ketone and water, not three. However if n-propyl alcohol and tert-propyl alcohol are mixed there are two substances because these two isomers are not in equilibrium due to the very low kinetic rate of interconversion between the isomers. It is a pragmatic decision based largely on what we get after simple physical separation methods such as distillation. --Bduke 05:35, 20 May 2007 (UTC)
replies: text: One definition of tautomerism (not quite the official one) is that two tautomers cannot be seperated by physical or chemical means, whereas two "normal" isomers can be. Most people would consider acetone to be a single chemical substance, even if it is a mixture of two molecular species. Physchim62 (talk) 09:14, 21 May 2007 (UTC)
thread_title: [[isomerism]] and [[tautomerism]]

message: I just created the entry for Reagent bottle. If you have more useful and knowledgeable information, please do add it. Radical Mallard (talk) 16:53, 6 July 2010 (UTC)
thread_title:  "Reagent Bottle" Entry Created - Please Add! 

message: The definition is given like this: "In chemistry, a chemical substance is a material with a specific chemical composition." "Chemical composition" links to Chemical compound, while chemical compound is said there to consist of two or more different chemical elements. (Say, oxygen consists of one.) Thus, the link is irrelevant. Jack who built the house (talk) 10:45, 30 November 2010 (UTC)
thread_title:  Logic 

message: I suggest to change the main definition to "A chemical substance is a form of matter that has  constant composition and characteristic properties. It can not be separated into components by physical separation methods, i.e. without breaking chemical bonds. Often, chemical substances are called pure substances to set them apart from mixtures".
The current definition reads "A chemical substance is a material with a specific chemical composition", with a citation to the IUPAC gold book. However, it is not carefully cited. The gold book has a longer definition that continues "Physical properties such as density, refractive index, electric conductivity, melting point etc. characterize the chemical substance". Leaving out this part distorts the meaning. According to the short definition, dioxygen and ozone would be the same substance (and all sets of allotropes), as would be ethanol and dimethyl ether (and all sets of isomers). It is difficult to find a definition that deals correctly with all borderline cases without getting overly long, but the current definition is too short to be accurate.
A good definition has to incorporate our understanding of a pure substance both at the macroscopic and the atomic level.
On the macroscopic level, a chemical substance has a constant composition (not specific composition, this would include a one molar sodium chloride solution, which is a mixture) and characteristic properties. It can not be separated into different components by physical methods such as evaporation, distillation, chromatography, zone melting or dialysis. A sodium chloride solution would not be classified as a chemical substance because it can be separated into pure sodium chloride and pure water, and because its physical properties such as density depend on the concentration of the solution.
On the atomic level, a chemical substance contains a set of atoms that have characteristic bonds to other atoms. No matter if a substance is a noble gas, a molecular compound, a solid ionic compound, a network solid, a metal or something more exotic, it is always possible to make a short list of atoms and describe how they are bonded to the other atoms in the list. The stoichiometry of the atoms in this list is constant, and the chemical formula of the substance summarizes that list. Every atom in the chemical substance is described by the list.
:For water in the gas phase, H2O(g), the list would be:
:# O, makes two covalent bonds to 2., with bent geometry
:# H, makes one covalent bond to 1.
:For sodium chloride in the solid phase, NaCl(s), the list would be:
:# Na, makes six ionic bonds to 2., with octahedral geometry
:# Cl, makes six ionic bonds to 1., with octahedral geometry
:For carbon, diamond allotrope, the list would be:
:# C, makes four covalent bonds to 1., with tetrahedral geometry
:For carbon, graphite allotrope, the list would be:
:# C, makes three covalent bonds to 1., with trigonal planar geometry
This is what the definition has to capture. Complications, such that water in the liquid phase partially dissociates, distract from the main idea, and should be dealt with further into the article. Similarly, the question of rapidly interconverting isomers, polymers with a range of chain length, isotopic composition etc. should be dealt with outside the lede.
--Theislikerice (talk) 04:04, 11 February 2011 (UTC)
thread_title:  A chemical substance is a material with a specific chemical composition? 

message: If you go to chemical compound it says much the same thing. The problem is that this is true only part of the time (i.e. for only some types of compounds). Yes, some chemical substances and chemical compounds have fixed ratios of atoms held together by chemical bonds (constant composition), but others do not-- and yet are clearly NOT mixtures. Atoms in a sample of matter may all be held together by ionic or covalent bonds, but they often, in fact usually do not have neat empirical formulas that you could write down on a bottle label. Most of the mantle and crust of our planet is such stuff--for example, all those plagioclase feldspars that don't have clearly defined stoichiometry. These articles are confused, as though minerology was all like biochemistry. We need to make it clear that whole-number stoichiometry sometimes happens, but usually it is just an ideal. Fixed ratios of atoms are the exception in nature, not the rule. These nice formulas are only a small subset of chemical substances and compounds in the "real" world.  SBHarris 06:43, 26 February 2012 (UTC)
replies: text: Editor Harris does us a great service in pointing out that we fail to adequately differentiate between substance and compound, instead allowing the loose usage in general chemistry textbooks to add to the addled thinking that always pervades web material. See the Definitions section, and below, for the beginning of distinctions, and discussion, toward a way forward. Le Prof.  71.201.62.200 (talk) 21:49, 2 July 2015 (UTC)
thread_title:  In chemistry, a chemical substance is a form of matter that has constant chemical composition and characteristic properties? Not always. 

message: Note, it is Wikipedia policy that it is sufficient to make statements in the lede that are substantiated, in the main body, through verifiable citations. It is for this reason that the lede does not bear any citations. The supporting citations for the lede appear in the main body of the article. Please, edit away, if you are a well trained chemist, or a chemical educator. If you do not understand the field, please discuss first. Cheers, Le Prof  71.201.62.200 (talk) 00:45, 24 August 2015 (UTC)
replies: text: There are about 10 citations in the definitions sections that underscore the content of the lede. The material of the lede is not unsourced, though further improvements to the definitions and other sections are indeed needed. I invite editors, rather than reverting, part and parcel, to improve the article by finding sources at odds with the content, and changing the content, or replacing poor sources with better ones, or adding sources where the  tags appear. (It was I that added the  tags, to earlier appearing text that remains poorly sourced. One cannot improve the whole of the article all at once.) Le Prof  71.201.62.200 (talk) 01:02, 24 August 2015 (UTC)
thread_title: Citations in main body of text sufficient 

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thread_title:  External links modified 

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thread_title: Assessment comment

message: Currently the definition is (version used at the moment of this comment):
: A chemical substance is a form of matter that has constant chemical composition and characteristic properties.[1] It cannot be separated into components by physical separation methods, i.e., without breaking chemical bonds[citation needed]. Chemical substances can be chemical elements, chemical compounds, ions or alloys.
1. First the IUPAC definition is not completely cited. This is important because when I read the complete definition of IUPAC, I have 
: Matter of constant composition best characterized by the entities (molecules, formula units, atoms) it is composed of
And when I look at the words of the definition, I can see that the plural form is used for molecules. Then there is no exclusion when citing the different entities of a substance. We can admit that a substance can be composed of one type of molecules like water as solvant with some ions like NaCl dissolved in it. So nothing in the IUPAC definition prevents to include mixture under the term of chemical substance.
But several constraints limits the use of chemical substance to only defined mixture. Aqueous solution of NaCl can't be considered as chemical substance because it doesn't respect the defined composition and the defined physical properties. But solution of NaCl 1M can be considered as a chemicla substance because the composiiton is defined and physical properties can be measured and compared.
2. Nothing in the IUPAC definition mention the characteristic of "it cannot be separated into components by physical separation methods, i.e., without breaking chemical bonds". In order to assess the validity of this additional definition, a reference has to be provided: it is not correct to create a definition from different sources without providing the sources. If there are different sources with different characteristics, this should be described in the definition section of the article and not merged into one WP definition in the introduction.
3. Then when citing the different classes which can considered as chemical substance, the alloys don't really fit with the "it cannot be separated into components by physical separation methods": some alloys can be partially melted in order to create a liquid phase rich in one metal and a solid phase poor with the same metal (see this diagram fo the copper-silver alloys). So if we agree that we can modify the composition of some alloys by melting and/or crystallization (I am not familiar with metal chemitry), then we can't keep the "it cannot be separated into components by physical separation methods" as characteristics of the chemical substance (or we should remove alloys as part of chemical substance).
4. The list of subclasses for chemical classes is in contradiction with the IUPAC définition: ions and chemical elements can't be considered as chemical substance as we can't measure the density or the melting point of ions or chemical elements. In case of ions because we an't isolate pure ion forms, same for chemical elements (we don't measure the density of hydrogen atom but the one of dihydrogen molecule).  So the list sould be chemical compounds, alloys, simple substances (like dihydrogen, dioxygen,...) and mixtures which have a defined composition.
In my opinion we should rely only on the IUPAC definition in the introduction: IUPAC is the reference in chemical nomenclature so we should always considered this definition as the first one. Other definitions should be cited in the definition section with some elements about the application of the definition. For example, I don't think that ECHA definitions for chemical substance has any influence in Asia (if we exclude the commercial exchanges between Asia and Europe), so indicating ECHA definitions is kind of western or at least european oriented defition and cannot be considered with the same authority as for IUPAC. Same for textbooks. Snipre (talk) 03:21, 10 June 2017 (UTC)
thread_title:  Contradictions in the definition 

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thread_title:  External links modified 

message: Substance and body are disjunctive concepts. Since the terms are interrelated, I recommend the following supplement:
Even Aristotle distinguished between substance (substance) and form (body): the substance is the formless, rigid substance, the "underlying", the form (body) its shape. Wood and Marble eg are fabrics, the finished plate or sculpture the shape. The sand castle disintegrates the sand remains. Fabric and form are sides of a concrete individual thing and do not occur independently:
more material term	wood 	wood 	water	diamond	paper	air    	––      	rain 	glass	iron
more physical term	plate	dowel	beam 	crystal	sheet	balloon	electron	areal	glass	atom
Remarks:
*The distinction between body and substance follows those in extensive and intensive quantities (properties).IUPAC, goldbook
*No material without body, no body without material!
*To distinguish between body and substance: bodies can be halved (divided), substances not. So half a piece of chalk is like the whole of chalk. The section is less than the whole.
*With a compound noun is an object (thing) physically and material comprehensively designated, for example: water drops, steel nail, ...
Walmei (talk) 11:34, 1 July 2018 (UTC)
replies: text: Note: pending wp:consensus, I had removed this part from the article, because I think it doesn't really belong. Perhaps in Matter (philosophy). - DVdm (talk) 12:22, 1 July 2018 (UTC)
thread_title:  Differentiation of substance and body 

message: Why element sometimes called pure 2A02:C7F:C297:9A00:ED0E:40FF:76DC:376D (talk) 17:54, 27 February 2022 (UTC)
thread_title:  Science 

message: What is pure
 substances 2409:4056:191:575B:0:0:2710:A0B1 (talk) 00:34, 14 May 2022 (UTC)
thread_title:  Pure substance