Talk:Cohesion (chemistry)

Complete overhaul

Needs a LOT of work. Example: photo of Hg caption. The container it is in "sticks together" for the same reason! The reason the Hg "balls up" (lay term) is because the cohesive forces (within the Hg and within the glass) exceed the adhesive forces between the Hg and the glass.

What is all the stuff about construction materials doing here?Softwarestorage (talk) 23:33, 18 August 2008 (UTC)

I kept some of the original text but otherwise completely overhauled the article. I'm sure nobody minds, as there was a lot of BS before (diamond cohesion?). This is an important article and needs much more work. SamuelRiv 13:36, 5 November 2007 (UTC)

copy and pasted from else where Maxwellstragedy 01:12, 19 September 2006 (UTC)

This article really needs attention from an expert. I think I might tag this article. --Gabycs 00:55, 24 March 2007 (UTC)

Just tagged it. Also added an external link. This link could be very useful for citing as a reference. Highly recommend this link as a source!!!! --Gabycs 01:36, 24 March 2007 (UTC)

this definately needs to be double checked against a chemistry book. for one cohesion is not the reason for water droplets forming adhesion is... --user:alc173 5:31 9 September 2008 —Preceding unsigned comment added by 71.0.246.239 (talk) 21:31, 8 September 2008 (UTC) / :That doesn't match up with the adhesion article. And why did you remove the part about industrial use...? Sorry, I don't know much about chemistry, so I may be wrong... ^suzumebachi٭_secret 18:37, 14 July 2009 (UTC)

Talking to the wrong person, no wonder it didn't make sense... Sorry! ^suzumebachi٭_secret 18:39, 14 July 2009 (UTC)

section removal

Nothing wrong with this section as such - but it's describing 'cohesion' in a 'building sense' not a chemical sense - and as such many of the examples are those of adhesion eg paint.

==Industry applications==

The construction industry uses many materials that undergo a phase transition during installation and use. These include, but are not limited to the following:

• caulking
• firestop mortar
• concrete
• plaster
• spray fireproofing
• paint

Often, these building materials are required not just to be cast and occupy space. They must also stick and maintain a certain thickness or space. Paint typically does not require as much cohesion as caulking, as paint is applied much more thinly. High quality firestop mortars require extreme cohesion with the adhesion because they are often used in large wall openings, where the mortar must not only adhere to adjacent materials but also hold itself up, forming a wall in the plastic state, which must hold long enough to cure and convert to the solid state. The thicker the application, the more cohesion is required.

I've pasted it above - maybe someone else can work on it - most of may be better found in another article.

eg the sticking together of mortar is cohesion, but because of the phase change other things hold it together - such as interlocking crystals - I think it't best to leave out for now.

Specifically the paragraph has it right when it says

The construction industry uses many materials that undergo a phase transition

But these phase transitions include precipitation, crystallisation both of which give rise to more than just cohesive properties. As for paint - the binder (which is effectively glue) holds it together, holds the pigment in, and sticks it to the wall - the binders are usually/often long chain polymers which will be sticking primarily by adhesive forces, as well as interlocking, in addition to cohesion.

I think a rewrite explaining the need for cohesion to hold together the bulk of polycrystalline materials like plaster of paris, fire bricks is necessary - though it requires citations - specifically proof that the cohesive force is the major force.

Additionally all fired materials must be held together at least a little by sintering which is not cohesion.

I think plaster of paris is probably the best example of a cohesively held together builfing material - again with the possible disclaimer of interlocking.83.100.250.79 (talk) 18:38, 14 July 2009 (UTC)

See this http://books.google.co.uk/books?id=AcWJDJM6iwUC&pg=RA1-PA215&lpg=RA1-PA215&dq=plaster+of+paris+cohesion&source=bl&ots=URN1hAt_AR&sig=EyYvxJz_NexTfssdzF89rqq7TmI&hl=en&ei=9dZcSvGkGJu6jAfO_7TZDQ&sa=X&oi=book_result&ct=result&resnum=7 (or http://books.google.co.uk/books?id=AcWJDJM6iwUC&dq=plaster+of+paris+cohesion&source=gbs_navlinks_s page 215) -

Its possible that a new article or subsection is needed "frictional cohesion in enginering/construction/building"

Another example of cohesion is the use of drying (not curing lacquers) eg nitrocellulose lacquer. 83.100.250.79 (talk) 19:10, 14 July 2009 (UTC)

Merging

That's a good idea,actually adhension and cohesion are co-related,and if we can understand one better,other can be understood nicely.And it seems easy to contrast and compare between two. — Preceding unsigned comment added by Anki112279 (talk • contribs) 06:16, 23 October 2014 (UTC) Hell no! That idea sucks — Preceding unsigned comment added by 71.190.202.21 (talk) 20:11, 9 December 2011 (UTC)

No, this is an awful idea. They're not the same thing and will make it confusing when looking for either. Scheezo (talk) 22:52, 9 December 2011 (UTC)

No No No! Cohesion and Adhesion are regular test questions in Middle School and all it would do is confuse students. — Preceding unsigned comment added by 74.235.126.25 (talk) 01:07, 9 May 2012 (UTC)

No. It wouldn't make sense to do so. Njaohnt (talk) 20:14, 20 July 2012 (UTC)

OH, NO! I have just got this point from the Campbell Biology(the 9th edition) that it regards cohesion and adhesion as the same thing. ILuo Summer (talk) 14:19, 28 January 2014 (UTC)

I oppose a merger. I think adhesion requires an adhesive. Biscuittin (talk) 20:02, 25 November 2014 (UTC)

Picture

Astronaut Clayton Anderson watches as a water bubble floats in front of him on the Discovery during the STS-131 mission.

Maybe this picture is a better example for cohesion than the one with the Equisetum. In the picture with the Astronaut we have 100% cohesion. Hive001 contact 08:40, 2 May 2010 (UTC)

File:Clayton Anderson zero g.jpg to appear as POTD soon

Hello! This is a note to let the editors of this article know that File:Clayton Anderson zero g.jpg will be appearing as picture of the day on December 9, 2011. You can view and edit the POTD blurb at Template:POTD/2011-12-09. If this article needs any attention or maintenance, it would be preferable if that could be done before its appearance on the Main Page so Wikipedia doesn't look bad. :) Thanks! howcheng {chat} 20:14, 8 December 2011 (UTC)

Picture of the day

Cohesion is the action or property of like molecules sticking together, being mutually attractive. Water is strongly cohesive, as seen in this photo of a weightless "bubble" of water on board Space Shuttle Discovery. Note that the astronaut's image in the bubble is inverted because of refraction.Photo: NASA

Assessment comment

The comment(s) below were originally left at Talk:Cohesion (chemistry)/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

rated top as high school/SAT biology content - tameeria 14:29, 17 February 2007 (UTC)

Last edited at 14:29, 17 February 2007 (UTC). Substituted at 11:59, 29 April 2016 (UTC)