0:00Let's say I have a balloon.
0:03And in that balloon I have a bunch of
0:05particles bouncing around.
0:07They're gas particles, so they're floating freely.
0:10And they each have some velocity, some kinetic energy.
0:17And what I care about, let me just draw a few more, what I
0:23care about is the pressure that is exerted on the surface
0:27of the balloon.
0:28So I care about the pressure.
0:29And what's pressure?
0:30It's force per area.
0:32
0:36So the area here, you can think of it as the inside
0:39surface of the balloon.
0:40And what's going to apply force to that?
0:42Well any given moment-- I only drew six particles here, but
0:46in a real balloon you would have gazillions of particles,
0:50and we could talk about how large, but more particles than
0:54you can really probably imagine-- but at any given
0:57moment, some of those particles are bouncing off the
0:59wall of the container.
1:01That particle is bouncing there, this particle is
1:03bouncing there, this guy's bouncing like that.
1:06And when they bounce, they apply force to the container.
1:10An outward force, that's what keeps the balloon blown up.
1:14So think about what the pressure is going to be
1:16dependent on.
1:18So first of all, the faster these particles move, the
1:22higher the pressure.
1:23
1:31Slower particles, you're going to be bouncing into the
1:34container less, and when you do bounce into the container,
1:37it's going to be less of a ricochet, or less of a change
1:40in momentum.
1:41So slower particles, you're going to
1:45have pressure go down.
1:47Now, it's practically impossible to measure the
1:50kinetic energy, or the velocity, or the direction of
1:53each individual particle.
1:55Especially when you have gazillions
1:56of them in a balloon.
1:57So we do is we think of the average
2:00energy of the particles.
2:01And the average energy of the particles, you might say oh,
2:04Sal is about to introduce us to a new concept.
2:08It's a new way of looking at probably a very familiar
2:11concept to you.
2:12And that's temperature.
2:14Temperature can and should be viewed as the average energy
2:18of the particles in the system.
2:20So I'll put a little squiggly line, because there's a lot of
2:23ways to think about it.
2:24Average energy.
2:25
2:28And mostly kinetic energy, because these particles are
2:31moving and bouncing.
2:32The higher the temperature, the faster that these
2:35particles move.
2:36And the more that they're going to bounce into the side
2:40of the container.
2:41But temperature is average energy.
2:44It tells us energy per particle.
2:49
2:52So obviously, if we only had one particle in there with
2:57super high temperature, that's going to have less pressure
3:00than if we have a million particles in there.
3:02Let me draw that.
3:05If I have, let's take two cases right here.
3:12One is, I have a bunch of particles with a certain
3:16temperature, moving in their different directions.
3:22And the other example, I have one particle.
3:25And maybe they have the same temperature.
3:27That on average, they have the same kinetic energy.
3:29The kinetic energy per particle is the same.
3:32Clearly, this one is going to be applying more pressure to
3:35its container, because at any given moment more of these
3:38particles are going to be bouncing off the side than in
3:40this example.
3:41This guy's going to bounce, bam, then going to go and
3:43move, bounce, bam.
3:44So he's going to be applying less pressure, even though his
3:46temperature might be the same.
3:47Because temperature is kinetic energy, or you can view it as
3:51kinetic energy per particles.
3:53Or it's a way of looking at kinetic energy per particle.
3:55So if we wanted to look at the total energy in the system, we
3:59would want to multiply the temperature times the number
4:04of particles.
4:05And just since we're dealing on the molecular scale, the
4:08number of particles can often be represented as moles.
4:11Remember, moles is just a number of particles.
4:13So we're saying that that pressure-- well, I'll say it's
4:19proportional, so it's equal to some constant,
4:26let's call that R.
4:29Because we've got to make all the units work out in the end.
4:31I mean temperature is in Kelvin but we eventually want
4:33to get back to joules.
4:34So let's just say it's equal to some constant, or it's
4:36proportional to temperature times the number of particles.
4:41And we can do that a bunch of ways.
4:43But let's think of that in moles.
4:44If I say there are 5 mole particles there, you know
4:47that's 5 times 6 times 10 to the 23 particles.
4:50So, this is the number of particles.
4:52
4:55This is the temperature.
4:57And this is just some constant.
4:58
5:02Now, what else is the pressure dependent on?
5:04We gave these two examples.
5:06Obviously, it is dependent on the temperature; the faster
5:08each of these particles move, the higher pressure we'll
5:10have. It's also dependent on the number of particles, the
5:13more particles we have, the more pressure we'll have. What
5:16about the size of the container?
5:18The volume of the container.
5:20If we took this example, but we shrunk the container
5:23somehow, maybe by pressing on the outside.
5:26So if this container looked like this, but we still had
5:29the same four particles in it, with the same average kinetic
5:37energy, or the same temperature.
5:39So the number of particles stays the same, the
5:41temperature is the same, but the volume has gone down.
5:44Now, these guys are going to bump into the sides of the
5:47container more frequently and there's less area.
5:50So at any given moment, you have more force and less area.
5:54So when you have more force and less area, your pressure
5:56is going to go up.
5:57So when the volume went down, your pressure went up.
6:03
6:08So we could say that pressure is inversely
6:10proportional to volume.
6:12So let's think about that.
6:13Let's put that into our equation.
6:15We said that pressure is proportional-- and I'm just
6:22saying some proportionality constant, let's call that R,
6:26to the number of particles times the temperature, this
6:31gives us the total energy.
6:32And it's inversely proportional to the volume.
6:36And if we multiply both sides of this times the volume, we
6:39get the pressure times the volume is proportional to the
6:46number of particles times the temperature.
6:49So PV is equal to RnT.
6:51And just to switch this around a little bit, so it's in a
6:53form that you're more likely to see in your chemistry book,
6:56if we just switch the n and the R term.
6:58You get pressure times volume is equal to n, the number of
7:03particles you have, times some constant times temperature.
7:08And this right here is the ideal gas equation.
7:14Hopefully, it makes some sense to you.
7:15
7:21When they say ideal gas, it's based on this little mental
7:25exercise I did to come up with this.
7:27I made some implicit assumptions when I did this.
7:30One is I assumed that we're dealing with an ideal gas.
7:35And so you say what, Sal, is an ideal gas?
7:38An ideal gas is one where the molecules are not too
7:43concerned with each other.
7:44They're just concerned with their own kinetic energy and
7:46bouncing off the wall.
7:47So they don't attract or repel each other.
7:50
7:56Let's say they attracted each other, then as you increased
7:59the number of particles maybe they'd want to
8:01not go to the side.
8:02Maybe they'd all gravitate towards the center a little
8:04bit more if they did attract each other.
8:06And if they did that, they would bounce into the walls
8:08less and the pressure would be a little bit lower.
8:10So we're assuming that they don't attract
8:11or repel each other.
8:13And we're also assuming that the actual volume of the
8:17individual particles are inconsequential.
8:20Which is a pretty good assumption, because they're
8:22pretty small.
8:22Although, if you start putting a ton of particles into a
8:28certain volume, then at some point, especially if they're
8:31big molecules, it'll start to matter in terms of their size.
8:34But we're assuming for the purposes of our little mental
8:37exercise that the molecules have inconsequential volumes
8:43and they don't attract or repel each other.
8:45And in that situation, we can apply the ideal gas equation
8:50right here.
8:52Now, we've established the ideal gas equation.
8:54But you're like, well what's R, how do I deal with it, and
8:56how do I do math problems, and solve chemistry
8:59problems with it?
8:59And how do the units all work out?
9:01We'll do all of that in the next video where we'll solve a
9:03ton of equations, or a ton of exercises with
9:06the ideal gas equation.
9:08The important takeaway from this video is just to have the
9:12intuition as to why this actually does make sense.
9:15And frankly, once you have this intution, you should
9:17never forget it.
9:17You should be able to maybe even derive it on your own.
0:00Let's say I have a balloon.
0:03And in that balloon I have a bunch of
0:05particles bouncing around.
0:07They're gas particles, so they're floating freely.
0:10And they each have some velocity, some kinetic energy.
0:17And what I care about, let me just draw a few more, what I
0:23care about is the pressure that is exerted on the surface
0:27of the balloon.
0:28So I care about the pressure.
0:29and เกิดความกดดัน
0:30it เป็นแรงต่อพื้นที่ 0:32
0:36so พื้นที่ที่นี่ คุณสามารถคิดว่ามันเป็น 0:39surface ข้างใน
0:40and ของบอลลูน สิ่งที่จะใช้บังคับได้
0:42well ขณะใดก็ตาม . . . ฉันเพียงแค่ดึงอนุภาคหก แต่
0:46in บอลลูน จริง คุณ จะ มี gazillions อนุภาค
0:50and เราสามารถพูดคุยเกี่ยวกับวิธีการที่มีขนาดใหญ่ แต่อนุภาคมากกว่า
0 :54you can really probably imagine-- but at any given
0:57moment, some of those particles are bouncing off the
0:59wall of the container.
1:01That particle is bouncing there, this particle is
1:03bouncing there, this guy's bouncing like that.
1:06And when they bounce, they apply force to the container.
1:10An outward force, that's what keeps the balloon blown up.
1:14so คิดเกี่ยวกับสิ่งที่ความดันจะ 1:16dependent
.
1:18so ครั้งแรกของทั้งหมด เร็วกว่าอนุภาคเหล่านี้ย้าย
1:22higher ความดัน .
1 : 23
1:31slower อนุภาคจะเด้งเข้าไป
1:34container น้อยลง และเมื่อคุณตีกลับลงในภาชนะ ,
1:37it จะ จะน้อยกว่าของแฉลบหรือน้อยกว่าของการเปลี่ยนแปลง
1:40in โมเมนตัม 1:41so ช้ากว่าอนุภาคจะ
1ความดัน 45have ลง
1:47now มันเป็นไปไม่ได้ในทางปฏิบัติเพื่อวัด
พลังงาน 1:50kinetic หรือความเร็วหรือทิศทางของแต่ละอนุภาค 1:53each
.
1:55especially เมื่อคุณมี gazillions
1:56of พวกเขาในบอลลูน .
1:57so เราทำคือ เราคิดว่า ของ 2:00energy เฉลี่ย
2:01and ที่ของอนุภาค พลังงานเฉลี่ยของอนุภาค คุณอาจจะบอกว่า โอ ,
2 :04sal จะแนะนำเราให้แนวคิดใหม่
2:08it เป็นวิธีใหม่ของการดูอาจจะ 2:11concept คุ้นๆ
เพื่อคุณ 2:12and ที่อุณหภูมิ .
2:14temperature สามารถและควรจะถูกมองว่าเป็น
พลังงานเฉลี่ย 2:18of อนุภาคในระบบ ผมจะใส่เล็กน้อย
2:20so ไก่เขี่ยบรรทัด เพราะมีเยอะ
2:23ways ที่จะคิดเกี่ยวกับมัน 2:24average
2 : 25
2 พลังงาน28and ส่วนใหญ่พลังงานจลน์ เนื่องจากอนุภาคเหล่านี้
2:31moving และแสง .
2:32the สูงกว่าอุณหภูมิ เร็วกว่าที่ 2:35particles เหล่านี้
2:36and ย้าย มากกว่าที่พวกเขาจะตีกลับเข้าด้านข้าง
2:40of ภาชนะ อุณหภูมิ 2:41but เป็นพลังงานเฉลี่ย 2:44it บอกเรา
2 : 49 พลังงานต่ออนุภาค 2:52so แน่นอน ถ้าเรามีหนึ่งในอนุภาคมี
2 :57super high temperature, that's going to have less pressure
3:00than if we have a million particles in there.
3:02Let me draw that.
3:05If I have, let's take two cases right here.
3:12One is, I have a bunch of particles with a certain
3:16temperature, moving in their different directions.
3:22And the other example, I have one particle.
3:25And maybe they have the same temperature.
3:27that เฉลี่ย พวกเขามีพลังงานจลน์เดียวกัน
3:29the พลังงานจลน์ต่ออนุภาคเป็นเหมือนกัน
3:32clearly หนึ่งนี้จะใช้แรงดันมากกว่า
3:35its ภาชนะ เพราะในช่วงเวลาของ 3:38particles เหล่านี้
จะกระดอนออกด้านข้างมากกว่า
3:41this ตัวอย่าง 3:40this . ผู้ชายจะเด้ง แบม งั้นไป
3:43move เด้ง อ้ำ . . .
3 :44so เขาจะใช้ความดันน้อย แม้ว่า 3:46temperature ของเขา
อาจจะเหมือนกัน อุณหภูมิ
3:47because เป็นพลังงานจลน์ หรือคุณสามารถดูเป็นต่ออนุภาคพลังงาน 3:51kinetic
.
3:53or มันเป็นวิธีการมองพลังงานจลน์ต่ออนุภาค .
3:55so ถ้าเราอยากดูที่พลังงานทั้งหมด ในระบบเรา
3:59would ต้องการคูณตัวเลข
4 : อุณหภูมิครั้งอนุภาค 04of .
4:05and เพียงเพราะเรากำลังเผชิญในระดับโมเลกุล ,
4:08number อนุภาคมักจะสามารถแสดงเป็นไฝ .
4:11remember ไฝเป็นเพียงจำนวนของอนุภาค .
4:13so เราว่า ความดัน . . . เอ่อ ผมจะบอกว่ามัน
4:19proportional จึงเท่ากับบางคงที่
4:26let , เรียกว่า R .
4:29because เราต้องให้ทุกหน่วยงานทำงานในที่สุด .
4 :31I mean temperature is in Kelvin but we eventually want
4:33to get back to joules.
4:34So let's just say it's equal to some constant, or it's
4:36proportional to temperature times the number of particles.
4:41And we can do that a bunch of ways.
4:43But let's think of that in moles.
4:44If I say there are 5 mole particles there, you know
4:47that's 5 times 6 times 10 to the 23 particles.
4:50So,นี้คือจำนวนของอนุภาค
4 : 52 4:55this คืออุณหภูมิ .
4:57and นี้เป็นเพียงบางส่วนที่คงที่ 4:58
5:02now อะไรคือแรงดันขึ้นอยู่กับ ?
5:04we ให้สองตัวอย่างนี้ .
5:06obviously มันขึ้นอยู่กับอุณหภูมิ ; ได้เร็วขึ้น
5:08each เหล่านี้อนุภาคเคลื่อนที่ ยิ่งกดดันเรา
5:10have . มันก็ขึ้นอยู่กับจำนวนของอนุภาค ,
5อนุภาค 13more เรายิ่งกดดันเราก็มี อะไร
5:16about ขนาดของภาชนะ ?
5:18the ปริมาตรของภาชนะ 5:20if เราเอาตัวอย่างนี้ แต่เราหดคอนเทนเนอร์
5:23somehow บางทีกดด้านนอก
5:26so ถ้าตู้นี้ดูอย่างนี้ แต่เราก็ยังได้
5:29the เดียวกันสี่อนุภาคในนั้นด้วยเช่นเดียวกัน โดยเฉลี่ย 1
5:37energy หรืออุณหภูมิเดียวกัน .
5 :39So the number of particles stays the same, the
5:41temperature is the same, but the volume has gone down.
5:44Now, these guys are going to bump into the sides of the
5:47container more frequently and there's less area.
5:50So at any given moment, you have more force and less area.
5:54So when you have more force and less area, your pressure
5:56is going to go up.
5:57So when the volume went down, your pressure went up.
6:03
6:08So we could say that pressure is inversely
6:10proportional to volume.
6:12So let's think about that.
6:13Let's put that into our equation.
6:15We said that pressure is proportional-- and I'm just
6:22saying some proportionality constant, let's call that R,
6:26to the number of particles times the temperature, this
6:31gives us the total energy.
6:32And it's inversely proportional to the volume.
6:36And if we multiply both sides of this times the volume, we
6:39get the pressure times the volume is proportional to the
6:46number of particles times the temperature.
6:49So PV is equal to RnT.
6:51And just to switch this around a little bit, so it's in a
6:53form ที่คุณมีแนวโน้มที่จะเห็นในหนังสือเคมีของคุณ
6:56if เราแค่เปลี่ยน n และ r . .
6:58you ได้รับแรงดันครั้งปริมาณเท่ากับ N จํานวน
7:03particles คุณมี บางครั้งเวลาอุณหภูมิคงที่ .
7:08and ตรงนี้ คือสมการก๊าซอุดมคติ 7:14hopefully
, มันทำให้ความรู้สึกบางอย่างกับคุณ .
7 : 15
7:21when บอกว่าก๊าซอุดมคติ มันขึ้นอยู่กับจิตนี้น้อย
7 :25exercise ผมมากับมัน .
7:27i ทำโดยปริยาย สมมติฐานที่ผมทำแบบนี้ .
7:30one คือผมสันนิษฐานว่า เรากำลังติดต่อกับแก๊สอุดมคติ .
7:35and ดังนั้นคุณพูดอะไร ซาล เป็นแก๊สในอุดมคติ ?
7:38an แก๊สอุดมคติหนึ่งที่โมเลกุลจะไม่เกินไป
7:43concerned กับแต่ละอื่น ๆ .
7:44they กำลังกังวลกับพลังงานจลน์ของตนเองและ 7:46bouncing
7 : ปิดผนัง47So they don't attract or repel each other.
7:50
7:56Let's say they attracted each other, then as you increased
7:59the number of particles maybe they'd want to
8:01not go to the side.
8:02Maybe they'd all gravitate towards the center a little
8:04bit more if they did attract each other.
8:06And if they did that, they would bounce into the walls
8:08less and the pressure would be a little bit lower.
8:10So we're assuming that they don't attract
8:11or repel each other.
8:13And we're also assuming that the actual volume of the
8:17individual particles are inconsequential.
8:20Which is a pretty good assumption, because they're
8:22pretty small.
8:22Although, if you start putting a ton of particles into a
8:28certain volume, then at some point, especially if they're
8:31big molecules, it'll start to matter in terms of their size.
8:34But we're assuming for the purposes of our little mental
8:37exercise that the molecules have inconsequential volumes
8:43and they don't attract or repel each other.
8:45And in that situation, we can apply the ideal gas equation
8:50right here.
8:52Now, we've established the ideal gas equation.
8:54But you're like, well what's R, how do I deal with it, and
8:56how do I do math problems, and solve chemistry
8:59problems with it?
8:59And how do the units all work out?
9:01We'll do all of that in the next video where we'll solve a
9:03ton of equations, or a ton of exercises with
9:06the ideal gas equation.
9:08The important takeaway from this video is just to have the
9:12intuition as to why this actually does make sense.
9:15And frankly, once you have this intution, you should
9:17never forget it.
9:17You should be able to maybe even derive it on your own.
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