What are the main differences? Volume, shape, or what?

  • $\begingroup$ Although there are some physical aspects, but you would get more good answer if you write this question on chemistry stack exchange. $\endgroup$ – Jack Rod Jan 27 '20 at 8:54
  • $\begingroup$ And secondly what you have done to find the difference, if you do little bit research you will get it, and if further also if you didn, t understand any topic search it on main site, and then too you have any doubt then post the question, posting the question without doing any work will be waste your as well as other time. $\endgroup$ – Jack Rod Jan 27 '20 at 8:56
  • $\begingroup$ I don't think you will get answer on Chemistry SE unless you show some effort. The question in by the way subtle although probably it wasn't intended to be. $\endgroup$ – Alchimista Jan 27 '20 at 9:05
  • $\begingroup$ At least makes title and text compatible to each other.... $\endgroup$ – Alchimista Jan 27 '20 at 9:17
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    $\begingroup$ @YuvrajSingh... I disagree with you comment. This issue is entirely a problem of physics. It has nothing to do with the fomation of chemical bonds (and even that would had been considred Physics by P.A.M. Dirac) but with their variation with the environment. $\endgroup$ – GiorgioP Jan 27 '20 at 10:02

While in a dilute gas the intermolecular distances are about one order of magnitude larger than nearest-neighbors distances in a molecule, this is not the same in liquid and solid phases. This is the reason one could expect variations of physical molecular properties with the environment. The site you cited in a comment does not directly address the issue of the modifications of one molecule as a function of different condensed phases. Unfortunately, it is not easy to find a comprehensive discussion of this point in textbooks.

Here, I can list and briefly discuss a few issues.

First of all, condensed phases include phases under very high pressure, then, from dilute gases to a very dense phase, there is a continuum of average configurations. But, while in a dilute phase molecular identities are quite obvious, in a dense phase, identification of individual molecules may become impossible. In the so-called molecular liquids or solids, there is a visible separation between intra- and inter-molecular distances, allowing to speak about molecules. However, even in such cases, experiments under pressure may eventually blur the individual molecules.

Even without the effect of pressure, the chemical environment, changing the interactions, may modify molecular properties as measured in vacuum. This is true for bond lengths and angles, but also for electronic properties like molecular polarizabilities. In general it is an interesting and non simple exercise to try to connect condensed phase properties with their isolated molecule counterparts. Since thee are many properties which could be used to discuss quantitatively this issue, I would leave a discussion to more specific questions.


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