Physics - Thermodynamics 2: Ch 32.1 Def. and Terms (22 of 25) PVT Surfaces for Real Substances

[@Forsnacke]

Awesome visualization! Never encountered this representation before. It is a useful tool for enhancing the intuition.

[@kega4062]

This is the best explanation I've heard, thank you!

[@MichelvanBiezen]

Glad it was helpful!

[@asideathring6111]

Sir i feel the diagram is incorrect cuz below a certain pressure liquid state can't exist and thus tends to directly convert to vapour so the bottom portion is vapour state ie S+V and not liquid. I mean the region below the triple line of pv diagram. Sir please do confirm if it's correct cuz its just an idea from practical observation

[@givenopinion]

Sir, very good explanation. How can I build this diagram for a specific component? Can I use the cubic form of Peng-Robinson equation for example and build a graph PvsT? Like for different values of P and T get the density or Volumen of gas.

[@MichelvanBiezen]

The best way to do that is to set up a table of values. (this can be tricky to visualize)

[@abdenshaker1963]

Dr why is in the some case the saturation pressure is the same vapor pressure

[@MichelvanBiezen]

In an enclosed environment, if there are just as many molecules escaping from the liquid as there are reentering the liquid, we can say that the vapor pressure is saturated.

[@yigitcan824]

Professor I have a question why subscript *g* is is used when looking for properties of vapor ,I mean this *g* comes from the first letter of _gas_ right?But gas and vapor are different things?

[@MichelvanBiezen]

Yes, g is used for gas and yes, gas and vapor are different. In a gas, the molecules are completely independent, in a vapor, the molecules are in an equilibrium state between a gas and a liquid and can be infused into the air without changing the relative abundance of the components of the air (which is not so for a gas)

[@yigitcan824]

@@MichelvanBiezen Oh I see ,thanks a lot teacher.You are great

[@amitjena2503]

a frictionless heat engine can be 100percent only it's exhaust temp is? a-0degree, b-0kelvin, equal to input temp, half of input temp.

[@MichelvanBiezen]

The answer is "B". The exhaust temp must be at 0 K.

[@jinogregary4317]

Does it goes from gas to solid above the critical temperature for any substance (co2)

[@entertainment-dv5zk]

Thank u professor( from INDIA)

[@MichelvanBiezen]

Welcome to the channel!

[@amitjena2503]

sir, I love your lectures.. I have some doubts from this chapter please make me clear if you have time... question -2moles N2 at 27degree Celsius mix with 1mole of He has at -73degree Celsius then find temp mixture.

[@MichelvanBiezen]

[(2)(300)(5/2) + (1)(200)(3/2)] / (2 x 3) = 283K

[@ammarahrais4546]

I know this is an old video but I would really appreciate if someone could clear my doubt. It seems counter-intuitive to think that the lower the temperature, the more change in pressure is needed to change from liquid to solid phase. From experience, I'd have thought its easier to change a liquid to solid at lower rather than higher temperatures

[@MichelvanBiezen]

First of all, water behaves differently compared to all other substances, so we cannot apply what we experience with water to other substances. But in general, higher temperatures cause atoms to vibrate more in solids, move faster and more erratic in liquids, and move faster as gas molecules. Thus at higher temperatures it requires more pressure to push the molecules back into a solid form. With ice however, higher pressure will cause it to melt.

[@ammarahrais4546]

​@@MichelvanBiezen Thank you so much for replying so quickly sir! Your lecture was very informative. I'm sorry I'm a little slow and a bit confused. In the video, you said at lower temperatures a higher change in pressure is required to push the liquid into a solid as compared to higher temperatures. But in your reply, you said at higher temperatures more pressure is required. From what I can understand, at lower temperatures the molecules are moving slower and thus have lower pressures exerting on the walls of a boundry. So the 'change in pressure' will be higher but the applied pressure needs to be lower?

[@MichelvanBiezen]

I think you are confusing a PT diagram with a PVT diagram. That is why the concepts take a bit of time to absorb. Note the slope of the liquid-vapor surface. To keep the volume constant at higher temperatures, you need greater pressure which is why that slope exists, which means you'll need less additional pressure at higher temperatures to reach the solid state.

[@user-dr5qs2oc5n]

Dear sir, what is the difference between vapour and gas? thanks

[@MichelvanBiezen]

Gas is a state of matter where each molecule is completely independent of every other molecule and behave under the thermodynamic principles of a gas. A vapor is a balance between a gas and a liquid which means that in a vapor some molecules my cling together in very small droplets. A vapor will condense into a liquid under increased pressure, where a gas will simply become more dense.

[@user-dr5qs2oc5n]

thank you so much

[@ahsansingh5260]

Good explanation.

[@thalakalasaradhi7857]

Thx a lot

[@MichelvanBiezen]

You're welcome!

[@thalakalasaradhi7857]

@@MichelvanBiezen ☺️☺️

[@shivasmart967]

tq sir

[@qnadss]

thank you so much!

[@MichelvanBiezen]

You're welcome!

[@manelcanales1541]

Dear Sir, thank you very much for your awesome instructive videos. However, I have noticed that there are two mistakes in this lecture. The first one is that below the triple line we really have solid-vapor coexistence, but never a liquid phase as you stated. Therefore, we have a triple line, and not only a triple point (this is the second mistake), where the three phases coexist. You can check it, for example, at the following link hyperphysics.phy-astr.gsu.edu/hbase/thermo/pvtsur.html Thank you very much for your attention.

[@ThomasJackson-s2h]

Waters Point

[@BarbaraLee-g7t]

Bernita Underpass