• finitebanjo@lemmy.world
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    23 days ago

    Each individual molecule did reach an excited state and entered the air, as the air molecules themselves are already highly excited. Also, if the air already has enough moisture then the moisture molecules in the air can accumulate on surfaces that are cold enough that they lose their excited state energy, and a puddle could remain even in warm temperatures because as water leaves the puddle more can also accumulate there.

  • Aceticon@lemmy.world
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    23 days ago

    Hence why there’s “boiling” and there’s “evaporating” - two things that aren’t the same hence two different words.

  • SorteKanin@feddit.dk
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    23 days ago

    My chemistry teacher once explained it to me like below. Does anyone know how much truth there is to this explanation?

    Temperature as measured by a thermometer or your finger is an average. Not every single molecule has the same temperature. The molecules constantly bounce around, smashing into each other, transferring heat to each other. By chance, some molecules will get hit in just the right way by other molecules to reach a very high temperature and then it evaporates. So there is constantly a gradient of temperatures among the molecules and the ones with the highest temperature are the ones evaporating, until there is no liquid left at all.

    As the average temperature increases, the chance of some molecules reaching a high enough temperature also increases, so warm water evaporates faster than cold water.

    This also explains why evaporation cools down (like when you sweat): the molecules with the highest temperature are the ones evaporating, so the average temperature decreases as those high-temperature molecules leave the system. Only the relatively colder molecules are left behind - thus it cools as a whole.

    • dwindling7373@feddit.it
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      23 days ago

      I think it’s much easier and truthful to stop talking about temperature and introduce speed in that context.

      The average speed is what we percieve as temperature, but single molecules can be fast, so fast as to break the boundaries of the liquid pool and shoot up toward space.

      Single unbounded molecules are what gas is.

      • SorteKanin@feddit.dk
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        23 days ago

        But temperature is not just the speed of a molecule right? Isn’t it also like the “energy” stored in the molecule, or its “wiggling” or something? Like a molecule moving very fast through space can still be at a very low temperature, right?

        • thebestaquaman@lemmy.world
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          23 days ago

          What you’re thinking about is the relation between energy, temperature, and heat capacity. When you add energy to a system (e.g. heat) the amount of energy you need to heat it up a certain amount is described by its heat capacity. If your molecules can “wiggle” (i.e. they’re multi-atomic) a portion of the energy you’re adding will go to increasing the “wiggling” rather than the mean speed of the molecules.

          What we perceive as temperature is related to the mean speed of the molecules, so because molecules that can “wiggle” more will require more heat to see the same increase in mean speed as non-wiggling molecules (because some of the heat is going to increasing the wiggling) they have higher heat capacity.

          It should also be mentioned that even the concept of temperature is really a statistical concept, so it doesn’t really make much sense to talk about the temperature of a single isolated molecule, or even a pair of them. Temperature as a concept starts to be fruitful to talk about in the thermodynamic limit which classically means “a whole shitload of molecules”, but (relatively) recent research suggests “a whole shitload” can be as little as 10-30 molecules. Once you go below the thermodynamic limit, we’re not really talking about the temperature of a system, but it’s energy, which is still well defined (although definitions may vary depending on context). Depending on who you ask, it can make sense to define a temperature also for single-particle systems, but at that point we’re talking about applying thermodynamic definitions that work (and are correct in the macroscopic limit) and no longer about what we classically perceive as temperature.

        • dwindling7373@feddit.it
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          22 days ago

          Wait it’s all models? Always has been.

          It’s kinetic energy, temperature itself is not a real thing, you are dealing with the bonds that keep water molecules together, if you wiggle hard enought, with enough energy (so… fast enough?) you break free.

          I guess another way to look at it is the cloud of elecrons getting more and more messy, so that it destabilizes the bonds…

        • Asetru@feddit.org
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          23 days ago

          But temperature is not just the speed of a molecule right?

          It pretty much is.

          Like a molecule moving very fast through space can still be at a very low temperature, right?

          That very much depends on the relative speed of the molecule and you. If you’re not moving in relation to the molecule, a collision between you and it won’t do much. Now try being hit by it (or a bunch of them) at high or even relativistic speeds. The area of you that’s hit will surely become pretty hot then.

          Like, have you seen footage of asteroid impacts? Have you seen shooting stars? Those are hot. Like, non-figuratively.

      • Snowclone@lemmy.world
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        22 days ago

        Next explain what mass is in 10,000 words or less. I know two whole ass physics classes aren’t enough, so. I’m trying to be generous.

    • BehindTheBarrier@programming.dev
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      23 days ago

      There’s a bit more to it, but it’s because of this effect.

      There is actually a balance between liquid and gas state, just overwhelmingly in favor of liquid when at normal temperatures. There is a ratio of molecules that will hit each other and transition to gas, and an equal amount gas hitting liquid and condensing. At least when there is a balance between the two sides, aka 100% moisture in the air. Which is not how it is most places.

      Normally there is always evaporated water in the air, and anything that evaporated will be moved away in any mildy ventilated area, as you say, it leaves the system. So it never reaches a balance, which is why things dry up at lower temps as water will always evaporate and leave the system.

    • Chamomile 🐑@furry.engineer
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      22 days ago

      @SorteKanin

      This also explains why evaporation cools down (like when you sweat): the molecules with the highest temperature are the ones evaporating, so the average temperature decreases as those high-temperature molecules leave the system. Only the relatively colder molecules are left behind - thus it cools as a whole.

      The main principle at work here is the enthalpy of vaporization. When matter changes state, there is an associated amount of energy that is absorbed or released - in the case of vaporization, energy must be absorbed. So when sweat forms on your skin and evaporates, it absorbs heat energy from your body in order to undergo that state change.

      For water, the energy involved here is remarkably high, much higher than the energy stored by a few degrees difference in temperature. For example, if you wanted to boil off 1kg of water, it would take about 300 kJ to bring the temperature up to boiling from room temperature and over 2000 kJ to boil it all into steam.

    • Ashelyn@lemmy.blahaj.zone
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      22 days ago

      In dry climates, the water actually will dry itself relatively quickly as long as there’s not an overwhelming amount. In more humid areas though, yup.

      • sugar_in_your_tea@sh.itjust.works
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        22 days ago

        Yup, I live in a desert climate and only clean up big puddles. Anything that doesn’t make a splash when I step on it will be gone in under an hour, probably closer to 15 min.

    • Asafum@feddit.nl
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      22 days ago

      Well, water does evaporate at less than 212° at the surface. It’s just that the entirety of a pot of water will boil if it reaches 212.

      Just think about puddles or whatever after rain on a metallic surface or concrete. It’s not entirely being absorbed or cleaned up by anyone.

  • Echo Dot@feddit.uk
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    23 days ago

    What exactly is this idiot suggesting some sort of conspiracy to hide all the water?

    Obviously the water fairies take it.

  • psud@aussie.zone
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    23 days ago

    The reason being that at any temperature where a liquid can be a gas (over zero degrees Celsius at standard pressure) some of that liquid will become gas.

    Over time all of the liquid will become gas

    • Echo Dot@feddit.uk
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      23 days ago

      And the reason for that is because the concept of temperature doesn’t really work when you’re talking about individual molecules. The average temperature might be 10° C but an individual molecule may very well get up to evaporation temperature, of course at that scale it doesn’t really do anything other than disassociate itself from its neighbors.

  • OneMeaningManyNames@lemmy.ml
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    23 days ago

    He rather questions modus ponens? Things can have many causes, that is why the presence of the effect in absence of the cause does not mean there isn’t a causal effect. Rain makes grass wet, even if the grass is wet without it having rained first, because there are presumably many reasons the grass can be wet (eg sprinklers), even if they are unknown to us. That having been said, this specimen is a hilarious face palm, all the same.