What Happens When a Liquid Turns Supercritical?

00:05:55
https://www.youtube.com/watch?v=zv4sE7R8QO4

Résumé

TLDRDans cette vidéo, l'auteur explique le concept de fluide supercritique en utilisant le xénon comme exemple. Il montre comment le xénon peut être transformé d'un état gazeux à un état supercritique en modifiant la température et la pression. L'auteur illustre également la différence entre un liquide, un gaz et un fluide supercritique, en démontrant les transitions de phase à l'aide de diagrammes de phase. Il aborde la distinction entre un gaz et une vapeur, en précisant que la vapeur peut être condensée en liquide sous pression, tandis qu'un gaz ne peut pas. La vidéo se termine par une invitation à s'abonner pour plus de contenu.

A retenir

  • 🔍 Un fluide supercritique est un état unique entre liquide et gaz.
  • 💧 Le xénon peut devenir un fluide supercritique à 60 atmosphères.
  • 📉 La température et la pression influencent les phases de la matière.
  • 📊 Les diagrammes de phase montrent les transitions entre phases.
  • 🌡️ L'eau se transforme en vapeur à 100°C sous pression atmosphérique.
  • 💨 La vapeur d'eau peut se former à des températures inférieures à 100°C.
  • ⚖️ Un gaz ne peut pas être condensé en liquide sous pression.
  • 🔬 Les fluides supercritiques ont des applications en extraction et purification.

Chronologie

  • 00:00:00 - 00:05:55

    Dans cette vidéo, l'auteur explique la différence entre un liquide et un gaz, en utilisant de l'eau comme exemple. Il introduit ensuite le concept de fluide supercritique, en montrant deux échantillons de gaz xénon, l'un dans un état normal et l'autre dans un état supercritique. En refroidissant le gaz, il démontre la formation d'une phase liquide distincte, illustrant ainsi la transition entre les phases. L'auteur compare également le comportement du xénon à celui de l'eau lorsqu'elle est chauffée, soulignant que le xénon ne montre pas de phase de vapeur distincte avant d'atteindre l'état supercritique. Il aborde ensuite les diagrammes de phase, expliquant comment ils représentent les différentes phases d'une substance en fonction de la pression et de la température, et comment ils montrent la transition entre liquide et gaz. Enfin, il discute des différences entre un gaz et une vapeur, concluant sur l'importance de ces concepts en ingénierie chimique.

Carte mentale

Vidéo Q&R

  • Qu'est-ce qu'un fluide supercritique ?

    Un fluide supercritique est un état de la matière qui n'est ni un liquide ni un gaz, mais qui présente des propriétés des deux.

  • Comment le xénon devient-il un fluide supercritique ?

    Le xénon devient un fluide supercritique en augmentant la pression et en abaissant la température.

  • Quelle est la différence entre un gaz et une vapeur ?

    Une vapeur peut être condensée en liquide sous pression, tandis qu'un gaz ne peut pas.

  • Que montre un diagramme de phase ?

    Un diagramme de phase montre les phases d'une substance en fonction de la température et de la pression.

  • À quelle température l'eau se transforme-t-elle en vapeur ?

    L'eau se transforme en vapeur à 100°C à pression atmosphérique.

  • Pourquoi la vapeur d'eau peut-elle se former à des températures inférieures à 100°C ?

    La vapeur d'eau peut se former à des températures inférieures en raison de l'interaction avec l'air ambiant.

  • Quelle est la pression critique du xénon ?

    La pression critique du xénon est beaucoup plus basse que celle de l'eau.

  • Comment un fluide supercritique est-il utilisé ?

    Les fluides supercritiques sont utilisés dans diverses applications, y compris l'extraction et la purification.

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Sous-titres
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Défilement automatique:
  • 00:00:00
    hey everyone today I'm going to be
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    showing you what a super critical fluid
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    is so we all know the difference between
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    a liquid and a gas right you can see
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    that this has some water in it so
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    there's a liquid at the bottom there's a
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    gas at the top and you can see that
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    there's a meniscus that forms now gases
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    will fill the volume of the container
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    completely and then liquid stay at the
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    bottom and it will fill the container at
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    the lowest point but now I want to show
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    you something that's not really a liquid
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    and not really a gas it's called a super
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    critical fluid in both of these vials I
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    have some xenon gas this is xenon gas in
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    a regular State and this is xenon gas in
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    a super critical state so right now this
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    is at around 60 atmospheres and room
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    temperature but I want to drop it to
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    around 16° C now I can do that by just
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    putting on a piece of ice but it's hard
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    to see cuz the ice is clear and the
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    vials clear and the liquid's clear so
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    it's hard to see everything so what I'm
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    going to be doing is just sticking it on
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    the Silly Putty here and then to drop
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    the temperature I'm just going to spray
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    this duster on it I'm sure you all know
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    if you turn these upside down you can
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    spray out the liquid and it's cold
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    liquid because it's evaporating so
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    here's the vial right now it's a super
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    critical fluid so there's no distinct
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    phase between the liquid and the gas
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    phase it's kind of one phase right now
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    that's neither liquid nor gas but now
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    let's cool it
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    down okay so I'm just going to cool it
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    down now there's a liquid in
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    [Music]
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    there so as I cool it down you
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    immediately see a cloud of liquid Xenon
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    form and the liquid drops to the bottom
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    and you can clearly see a meniscus which
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    means there's two distinct phases a
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    liquid and a gas now if this were a vial
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    of water like I have here and I heated
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    up the water the water would turn into a
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    vapor and you'd see the water boil and
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    the liquid layer would get less and less
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    and less until there were no liquid left
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    but that's not what happens with the
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    Xenon watch this as I heat it
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    up now if this weren't reaching a super
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    critical State you would normally just
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    see the liquid Xenon start to boil and
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    the liquid would get less and less as it
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    converts into a gas but watch how the
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    meniscus just kind of disappears the
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    liquid just kind of goes
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    away let's see this again and I'll shake
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    the liquid as it turns into the Super
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    critical
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    fluid so you can see there's clearly a
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    liquid in here I'm just going to wiggle
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    it back and forth and you can see it
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    sloshing
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    around can still see the meniscus but
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    it's kind of getting less clear and it's
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    you can still see waves but then it's
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    just kind of
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    gone can still see it sloshing a little
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    bit
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    actually then it's gone as a chemical
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    engineer I had always wondered about
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    super critical fluids and what it looks
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    like when they converted from a liquid
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    into a super critical fluid that is
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    crazy that looks so cool and in order to
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    fully understand what's happening here
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    and understand what the difference
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    between a gas and A vapor is I need to
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    introduce you to phase diagrams phase
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    diagrams are really useful they show you
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    what phase a certain substance is going
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    to be at a particular pressure and
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    temperature so for example this is the
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    phase diagram of water you can see that
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    at regular atmospheric pressure and room
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    temperature you're only going to have
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    liquid water you're not going to have a
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    vapor or a gas but as soon as you reach
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    100° C at atmospheric pressure then it's
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    going to start converting into a gas and
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    the temperature will not increase until
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    it's converted all the liquid into a gas
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    now I want to point out something
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    important here notice how I said that
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    you're not going to get any water vapor
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    at anything below 100° C and atmospheric
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    pressure so no matter how hot your
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    liquid is there's no water vapor above
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    it but that's probably a little
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    confusing to you because if you've ever
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    heated water on a stove you'll notice
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    that water vapor or steam starts to come
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    off of it at well below 100° C if you
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    bring out a pot of hot water into the
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    air you'll see Steam just pouring off of
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    it but the reason that's happening is
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    because you have water in air and the
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    mixture of water and air causes some of
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    the water vapor to come off of it and
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    mix into the air but if you have only
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    pure water contain in its own system and
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    heat it up it will not turn to a vapor
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    until it reaches 100° C at atmospheric
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    pressure on phase diagrams you have some
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    solid lines here and these solid lines
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    are what separate the different phases
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    of that particular substance but you'll
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    notice something with these solid lines
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    as you continue up the solid line
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    between liquid and Vapor you'll notice
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    that it just kind of ends once you get
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    past a certain pressure and temperature
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    there's no real distinction between a
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    liquid and a gas once it goes beyond
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    that point there's no longer two
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    different phases it's one single phase
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    called a super critical fluid but now
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    let's look at the phase diagram of xenon
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    so for Xenon it looks similar to water
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    but notice that the critical temperature
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    and pressure is much lower than for
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    water water in fact it's so low that if
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    you just pressurize it to around 60
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    atmospheres at room temperature then you
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    can get it to become a super critical
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    fluid so have you ever wondered what the
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    difference between a vapor and a gas is
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    a vapor means it's below this critical
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    point here so if you were to take a
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    vapor and pressurize it you could turn
  • 00:05:17
    it into a liquid but if you take a gas
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    and pressurize it you can't turn it back
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    into a liquid so at the temperatures
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    that we're used to dealing with water
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    it's always in the vapor State meaning
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    that if you pressurize it hard enough
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    you can turn it back into a liquid and
  • 00:05:32
    thanks for watching another episode of
  • 00:05:33
    the action lab I hope you enjoyed it if
  • 00:05:35
    you did don't forget to subscribe if you
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    haven't subscribed yet and you can also
  • 00:05:39
    hit the Bell so you can be notified when
  • 00:05:41
    I release my latest videos and thanks
  • 00:05:43
    for watching and I'll see you next time
Tags
  • fluide supercritique
  • xénon
  • phase
  • diagramme de phase
  • liquide
  • gaz
  • vapeur
  • pression
  • température
  • chimie