Temperature: Crash Course Physics #20
ฝัง
- เผยแพร่เมื่อ 29 เม.ย. 2024
- Bridges. Bridges don't deal well with temperature changes. In order to combat this, engineers have come up with some workarounds that allow bridges to flex as they expand or contract. In this episode of Crash Course Physics, Shini talks to us about temperature and the ideal gas law. Also, we figure out how much air is in your car.
--
Produced in collaboration with PBS Digital Studios: / pbsdigitalstudios
--
Want to find Crash Course elsewhere on the internet?
Facebook - / youtubecrashc. .
Twitter - / thecrashcourse
Tumblr - / thecrashcourse
Support CrashCourse on Patreon: / crashcourse
CC Kids: / crashcoursekids
We made quiz questions to help you review the content in this episode! Find them on the free Crash Course App!
Download it here for Apple Devices: apple.co/3d4eyZo
Download it here for Android Devices: bit.ly/3TW06aP
went from music physics to thermodynamics in one episode. that escalated quickly xD
Wuuuuuuuuuuuut! I had no idea about those cracks being because of expansion and contraction. That's slick. Learn something new like 10 seconds into a video. New record?
No. It took your age, plus 10 seconds.
Thank you for helping humanity learn about their home and laws that governs it.... 👍😁
I love this videos, especially how you use animations to visualize the equations. I hope there will be more about thermodynamics.
I simply LOVE to see this woman explain physics! She makes it even MORE fun to appreciate.
That sexist
+Luis Rodriguez
No, it isn't.
Great video! And you reminded me that Avogadro's number is 6.022 x 10^23!
I blame my afternoon drowsiness on that 5.2% less air
Such a brilliant platform!
Heres a question that sometimes racks my brain, when you're moving forward in a car and a fly comes in the window does it have to fly forward as fast as the car? or is the air in the car pushing the fly so it just has to maintain it's hover?
If the fly is entering the car from behind, it needs to fly faster than the car to reach it and enter the window. But once inside, the air inside the car moves at the same speed as the car, so it only needs to hover in the air to follow the car.
Love it!
Thank you CrashCourse, keep'em coming.
DO CRASH COURSE MATHEMATICS
The World Is Logic YEAH!
@@garnet4945 The World is Corona YEAH!
Thanks for doing these videos. I really appreciate them. 😊
This is literally one semester worth of applied physics compressed in 9 minutes (yesterday at school we saw ideal gases)
I love this physic teacher 😍 !
yeah shes pretty hot
Yup, she's super cool and hot! And i love her accent!
great job with the colorcoding of the variables, great job explaining everything and also great work doing a short video with A LOT of content. wins a sub in need for more.
My favourite statement of the ideal gas law:
P = N kT
N being the number density (inverse volume units) and k Boltzmann's constant.
I like it because it shows pressure being like an energy density and like a momentum density.
Small k for Kelvin, a small error. And it might have been nice to mention the microscopic version of the ideal gas law as well. Boltzmann constant has a few more uses than the ideal gas constant. But you can't squeeze in everything in 9 minutes. Maybe there will be a statistical physics lecture in the future ;)
Kelvin is big K
Thank you to help us. I also use Giancoli's book at the training teacher college.
In college, the way I remembered PV=nRT is that it sounds like saying "pervert" with your nose plugged.
Not that I was called pervert at college... well, not every day.
High school chem teacher taught it as perverted nerds. Lmao.
yea
You could also just learn why it's true lol
Thank you for the help!
214 moles in your car? Someone call the exterminator
Crota son of Oryx 😑😐Lame my friend. ..just lame
I have no regrets
NO REGRETS
lol
I laughed
GOOD TEACHING
An episode on Temperature.......So cool!!!
I love your videos please make more, you rock
Well put
4:16
i was wondering where the constants where at but it was behind the subtitles... lol
how to describe how much great it was? I have no words for that
crazy thing about temperature: a single particle can not have a temperature, there needs to be multiple particles/molecules/things moving around and bumping into eachother
3:36 I heard "Hank Hoes did" instead of "Hank hosted" I'm dying rofl
This channel is simply perfect... I can improve my english and review physics at the same time🧠❤️
It contracts in cooler weather so the metal thing in the bridge gets further so it will fall appart because it's going further apart so the bridge will fall
Great Turorial
could you please explain electrostatics, capacitor,current.... in detail?
New Seating Position?
Love your films
really cool vid
5.2% less air! Oh no!
I'm talking about 20º C of course
SECOND QUESTION. So, in the final example, if the car _was_ airtight, would that mean that the temperature inside couldn't change? That can't be right can it- the radiation should still give energy to the molecules inside. So then, does the constraint of Pinside = Poutside no longer hold true? Or, would the volume expand?
Nice!
way over my head. but I love it.
Love this series, it needs more praise by the fans. It's a shame most of the fans are just here for Hank and John. I love every series regardless the host and especially this one.
I was a big fan of Phil Plait and Astronomy too, I've liked his views on Nova and the like too
Hank brings more humor, imo. Shini just looks overly excited.
I can't listen to this while the Dingmans Ferry Bridge is stuck in my head. I can hear it, but the words aren't connecting, because the bridge they're describing is a fantasy.
One problem: if linear expansion of a solid is a(l_0)(∆T) and the area of the cross-section perpendicular to length has no reason to be fixed/to not follow the square of this equation, why isn't expansion of a solid V_0[(a)(∆T)]^3? Or if the volumetric expansion equation is accurately given, shouldn't linear expansion be l_0[(b)(∆T)]^(1/3)?
If anyone was wondering the bridge in the video at the start was moving like that because the wind caused it to vibrate at its resonant frequency.
Once again she's breaking the traffic rules, an equation I can't figure out with physics. 😱😱😏
PV=nRT, the only formula I remember from my chemistry and will likely never forget. lol
Is that an Overwatch Hover Car at 6:21?
How can the pressure remain constant with an increase in pressure in the car analogy given at the end? And how can number of moles of gas change in the airtight car?
Sorry if I'm being dumb, and thanks in advance :)
I wish she could speak a little more calm to let my brain absorb and process what she is saying.
its a crash course for a reason actually.
Then slow it down
@@aakashdharmakari2591 breathing for a second doesn't make it long...
wouldn't it have been easier to say that heat expansion has to do with the electron movements (heat) and that the expansion has to do with how high the electrons in an atom jump around, or would that be incorrect?
AAAAH I have that book!!!
THIS...helped in soo many ways for my finals. Thank You :)
Echo reduction material needs to be adjusted to compensate for Dr. Shini's new position/set.
Overwatch ARG at 6:20??
So, wait. At 4:30 you said as Temperature increases volume increases. Yet in the car example, the car has less moles when it is hotter? Moles equates to density right? So, I guess in that sense if mass is constant then higher density means lower volume. So I guess that would make sense. Do I have the right idea?
"Moles" are the "amount of atoms" inside the car.
So as the gas warms up, the density decrease, and a lower amount of gas atoms (moles) can cover the entire inside (volume) of the car.
So a warmer car has a lower amount (and mass) of air inside it, because the hot air has expanded and some of it has left the car.
what is the name of those 4 physics books on the top of stacked Feynman books?
I see that symmetra spray at 6:33
5:27 okay but in the video on heat, the formula is given as pv=nrt(3/2)
You guys need to do crash course CLIMATE CHANGE!
lol I went to Google maps to see if these expansion gaps exist, and I then found that I am continuing to watch the video a few weeks later.
Based upon the equations, it appears that exactly the same amount of energy is required to increase any given substance or system by one degree in temperature. Which makes perfect sense, but it gets to seem a bit crazy when scaled up or down, so I'd like to get some clarification, if someone would be so kind.
Given the amount of energy required to increase a kilogram of water by 1 degree celsius (1 kilocalorie, or 1 [large] Calorie), does that mean the same amount of energy will also increase a single gram of water by 1000 degrees celsius? (Barring a phase change, of course, which will change the specific heat of the substance. Assume ideal superheating, a perfectly closed system, etc.)
Basically, yes.
But when you start to actually get that kind of heat, all kinds of other effects start to apply. When you reach 100C, you have to spend a lot of energy on the phase change to gas. And once you are a gas, the same amount of energy do not increase the temperate the same amount as in the liquid (or solid) phase. The amount of energy required to increase the temperature by one degree also change slightly based on temperature within a phase, but this is mostly relevant for ridiculusly warm vapor.
This concept is usually refered to as "Heat capacity" for the matter you are warming, in case you want to research it further.
Thank you for the clarification. I suspected as much but it does seem quite outside of what one would expect, in such extreme circumstances.
Actually that is not correct specific heat capacities vary between materials, that is the amount of energy required to produce a given change in temperature in a given mass of the substance usually expressed in terms of J/K·g ie the amount of energy in Joules required to increase the temperature of 1 gram of the substance by 1 Kelvin. For water the value is 4.184 J/K·g, copper on the other hand has a specific heat capacity of 0.385 J/K·g. Thus water can actually absorb nearly 10.9 times the energy per unit mass than copper for the same change in temperature, the effect is of course somewhat smaller per unit volume since copper is 8.96 times the density of water but still it's 1.21 times the heat energy per unit volume.
Course how fast different materials actually heat up in practice depends on a whole host of other factors too for direct heat transfers mostly that would be the thermal conductivity though for fluids even the shape of the container or basin can be a factor due to the effects of fluid dynamics and convection. Things get even more complex when dealing with radiative transfers which is especially tricky when dealing with expansion in outdoor structure since of course the primary heat source (the Sun) is a radiative transfer and properties like reflectivity, emissivity and absorbtion can be affected by factors as basic as what colour paint you put on a material.
What about water it expands and contracts with temperature until it gets down to 4°C where it no longer contracts
i just leanded about those cracks at school
Temperature
Thermal expansion
Linear and volume expansion
Ideal gas law
Number of moles of air
While showing the formula for the ideal gas law in the upper right hand corner you still have it labelled as the Gay-Lussac's Law, as in the previous graphic.
do you have a vdo about thermal effect?
I have a question about temperature Shini. I can see how holding an open flame to your hand will burn your hand because the air molecules are moving so quickly that they will destroy your cells on impact. My question is how dose something like liquid oxygen immediately freeze your hand when there is very little kinetic energy in the liquid oxygen to react with your hand?
If two objects are touching, the rate of heat transfer between them is proportional to the difference in temperature. In the flame scenario, the molecules don't destroy your cells on impact (that would be something like alpha radiation), they just bounce off them and give them kinetic energy. The energy then tries to go somewhere, like up your arm or out the back of your hand, but it can't move faster than the flame is pumping in new energy, so the energy builds up in your hand, which destroys the cells.
With liquid oxygen, it's the opposite, your hand is the flame. The temperature difference is still really large though, so the kinetic energy is violently sucked out of your hand molecules, until the water molecules get slow enough that they start sticking to each other (freezing). When water freezes it makes really bulky, sharp-edged crystals, which rip apart the cells they form in.
Thanks Rhaegar19.
Dr. Somara, what is your favorite bridge?
your mom!!!! (hi)
hi!
London bridge
in the final example, won't the pressure decrease when temperature decreases and the ratio will be the same ???
Un dos tres Calipso
Un dos tres Calipso
Sing whit me !
Calipsooo
There are 11 moles of air less in the afternoon because of the higher temperature. Are we assuming that at some point between the morning and afternoon, a door was opened to allow an exchange of air with the outside? If the cabin is airtight and a door was never opened, then I can't see how there could be less moles in the afternoon.
Good point. Luckily, she specifically said that the car was not airtight.
Pretty cool :-)
shout out to the physics for scientist and engineers Giancoli textbook in the back there.
You guys should refer 6.02*10^23 as avagadros number bc it is far easier to remember
I agree, but remember these videos are addressed to audiences who may not have a prior knowledge in chemistry such as what Avogadro's Number is.
nerd!!!!!
*Avogadro
Yes! A teacher used avocados as an example. 6.02 x 10^23 avocados can make how much guacamole? It was weird, but it makes enough for 3.612 x 10^24 people...
Wow you gorgeous...I couldn't hear the words, their meaning, to be precise. Not fair, I came to learn!
They should have a radiometer on set
1:39 is it applicable for all objects around?
Can I get thermal properties of metirial *11th
ya whoop whoop
cool (sorry for my bad English)
Bruh, you literally just said one word dawg.
Do crash course sociology please!
The Linear expansion of a steel beam. (alpha)=(13x10^-6)/*C, (length)=3.66 metres, Temperature (of burning jet fuel)=1500*C.
(delta) L = (13x10^6/*C)(1500*C)(3.66m) = 7 cm.
This means a 540 metre (54'000 cm/138 story) building has 14'754 steel beams. If 20 stories (78 metres) are on fire that is 21.3 steel beams exposed to that temperature. That means each beam is now 3.73 metres by individual linear expansion. Multiply 3.73 metres by the 21.3 steel beams, and find a total linear expansion of 79.5 metres. That is a difference of 1 meter using linear expansion.
Can you explain why a soda can expands in a freezer or cold environment when you explain that the colder the temp, the smaller it should be.
Water is a weird exception to that rule because it forms really bulky crystals when it freezes. It starts expanding below 4C.
Hydrogen bonds :)
the hydrogen atoms are more positif and the oxigen atoms are negative.
when it is cold enough, the H2O molecules are moving less so that the molecules can attract eachother and form crystals. those crystals are less dense then liquid water because there is more space between the molecules, so the fluid expands
Not so much temperature this one, more ideal gases. Still good though 😀
Your concept and materials are strong...but videos are going too fast to understand even at 0.75*speed ...
Thanks for providing us so much knowledge and concepts used in daily life..which matters and also important...
But kindly make the complete videos on these topics so that we will understand even more from it
And it helps a learning student a lot...
Thanks again
...
When i learned it we used alpha for linear, gamma for volume and beta for area. Why would you skip area?
video length ? It is also pretty obvious to interpolate, isn't it ?
2:53, Symmetra? Is that you?
I was wondering when Avogadro's number would make an appearance in this series. Surprised yall didn't call it by name.
So will be die due to lack of air, just by raising the temperature enough? (Assuming we dont die of the heat)
I'm no expert but I think there's a slight problem with the explanation of the temperature increasing the volume. In the example, the gas was in a balloon (called a container) and it was said that increasing the temperature means making the molecules move faster, thus pushing out the container.
However, it was stated earlier that one of the assumptions of an ideal gas is that its volume is much less than that of the container. This raises the question, are we talking about the volume of the gas, or of the container?
Ohhh, I didn't see the video, but either you heard something wrong or they said something horribly wrong. One of the fundamental properties of gases is that they take up all the volume available to them. If you put a gas in a container, it will have the volume of the container, no matter what.
She only mentioned one solution for the linear expansion, but what about the volume expansion? 🙃
I wonder if there will be crash course mathematics, that could be interesting.
Aren't you supposed to calculate it with kPA not PA?
if this is how teachers are like outside of where i live then i hate this place
You guys haven't put this in the physics playlist yet.
Isn't linear expansion the same as volume expansion? Because a metal bar as it heats up will get larger, but will also become thicker. But the change in thickness is just irrelevant in relation to the change in length. Did I understood something wrong?
Its a good point - you're on to something. In addition to getting longer, the bar may indeed get "thicker" as well and depending on what you want the shape to do or what you permit the shape to do, say for engineering purposes, this change in thickness may be too big and cause trouble. Think of a shim in between two other shims, the middle shim is getting more compressed by the outer shims like a sandwich as it gets heated and gets "thicker" - the outer shims push back! Will it break and cause a bridge collapse? Thats what you will know how to answer if you take engineering and get paid for it to boot :)
As a more complete answer, the precise change of dimensions (call it dx,dy,dz) of any arbitrary shape at any point on the shape due to a temperature change is explained by more complete equations that not only consider the coefficient of linear thermal expansion in three dimensions (x,y,z) but also consider Poissons Ratio, Youngs Modulus and Shear Modulus for that material - I cant remember if theres any other properties you'd need, its been a while. Could there be a way to combine all these properties to get some "volume" coefficient of thermal expansion or has someone done experiments to find a volume thermal expansion for different solids? Probably. Or perhaps an alternate method like distortion energy could be used to determine the dimension changes. If all else fails, use computer simulations lol
hmmm, as I understood, the two expansion equations doesn't have sense when are considered together:
\Delta l = \alpha l_0 \Delta T
\Delta V = \beta V_0 \Delta T
if the solid is a cube, then V=l^3, and as \Delta l = l-l_0 then l=l_0+\Delta l, so
V=(l_0+\Delta l)^3=(l_0+\alpha l_0 \Delta T)^3
but also
V=V_0+\Delta V=V_0+\beta V_0 \Delta T
then
(l_0+\alpha l_0 \Delta T)^3=V_0+\beta V_0 \Delta T
If we expand, one side of the equation would have \Delta T^3 and the other one would have \Delta T, if we vary \Delta T but we let constant the rest it would be like saying that a polynomial of degree 3 is equal to a polynomial of degree 1.
Why the number of moles would decrease if it gets warmer?
we need english subtitle for this video
PV=nRT works regardless of the fact that air is composed of many different Molecules? I mean, 1 mol of Oxygen at atmospheric pressure occupies another volume than 1 mol of Nitrogen or 1 mol of CO2 do at the same pressure, right? Isn't the calculation kinda flawed for mixed gasses?
And thats why its ideal friend
Beefyhax
I'm a derp, thanks xD
No, because there is so much space between gasses at low temperature and pressure (not in a hot compressed gas) that all gas molecules are roughly the same shape and size as each other compared to the gas around them
Alex Tritt
So there is an other more complicated formula than the one mentioned above for higher temperature and pressure?
+Yunnik yes there is... I forgot exactly what it was though. There were like 2 other properties based on the particular gas that were included.