Why are there clear-cut states of matter instead of a gradual transition from gas to solid (let's set plasma aside for the purpose of this question)? If the main difference between them is the distance between molecules, then with temperature going down (let's neglect pressure for the purpose of this question), a gaseous substance should gradually become more and more liquid and then more and more solid, shouldn't it (as if God fiddles with a slider in his computer interface; let's set aside the question of God's existence for the purpose of this question)?

  • $\begingroup$ Are you asking like, why is there a liquid state? $\endgroup$
    – daydreamer
    Oct 13 '20 at 16:10
  • $\begingroup$ Phase transitions do not occur instantly on a macroscopic scale, observe a glass of liquid water placed in your freezer. $\endgroup$ Oct 13 '20 at 16:19
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    $\begingroup$ I think he's asking, why doesn't water in a heated pot just slowly expand until it's a gas -- what causes the sharp difference in properties. And similarly, why isn't there a stage in freezing where the water is sort of mushy and flexible, and it slowly becomes more solid. $\endgroup$
    – Luke
    Oct 14 '20 at 0:25
  • $\begingroup$ 1) "Why questions" are always hard a thing to deal with. Please, listen to Mr. Feynman youtube.com/watch?v=36GT2zI8lVA. After that, check these related great answers to almost the same thing you're trying to figure out physics.stackexchange.com/questions/268999/… and physics.stackexchange.com/questions/313758/… $\endgroup$
    – daydreamer
    Oct 14 '20 at 1:34
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    $\begingroup$ If not any of the above, does this answer your question? First and second order phase transitions $\endgroup$
    – daydreamer
    Oct 14 '20 at 1:49

Some substances do have a state that is intermediate between a solid and a liquid over a range of temperatures and pressures - its is called a mesophase. Liquid crystal displays are an application of mesophase materials.


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