[Bored chemist]

No multiplication by zero is involved.

Nobody said it was.

Did you notice that Alan got completely the wrong answer?
Do you consider that to be important?

[hamdani yusuf (OP)]

I already told you twice.

Which one?

Yes there is.
That is why I provided it.
Did you somehow miss this bit?

Quote from: Bored chemist on 13/04/2022 23:07:45
A xenon arc lamp  gives a fairly good approximation to thermal spectrum- unless you look near the emission lines at the right hand end
https://en.wikipedia.org/wiki/Xenon_arc_lamp#/media/File:Xenon_arc_lamp_profile.png

The visible radiation from the sun is close enough to a thermal spectrum to let us estimate the temperature of the sun's surface.

But the emission lines were what allowed someone to demonstrate the existence of helium

I think that something should be a noun.

[hamdani yusuf (OP)]

No multiplication by zero is involved.

Nobody said it was.

Your view is like saying that the top of a hill is flat and the bottom of the hill is flat so you can calculate the potential energy of an object at the top of the hill by multiplying the weight by zero.

[Bored chemist]

No multiplication by zero is involved.

Nobody said it was.

Your view is like saying that the top of a hill is flat and the bottom of the hill is flat so you can calculate the potential energy of an object at the top of the hill by multiplying the weight by zero.

You highlighted the wrong bit

Your view is like saying that the top of a hill is flat and the bottom of the hill is flat so you can calculate the potential energy of an object at the top of the hill by multiplying the weight by zero.

Nobody said it was actually doing it.

[Bored chemist]

I already told you twice.

Which one?

Yes there is.
That is why I provided it.
Did you somehow miss this bit?

Quote from: Bored chemist on 13/04/2022 23:07:45
A xenon arc lamp  gives a fairly good approximation to thermal spectrum- unless you look near the emission lines at the right hand end
https://en.wikipedia.org/wiki/Xenon_arc_lamp#/media/File:Xenon_arc_lamp_profile.png

The visible radiation from the sun is close enough to a thermal spectrum to let us estimate the temperature of the sun's surface.

But the emission lines were what allowed someone to demonstrate the existence of helium

I think that something should be a noun.

OK, fair enough.
It depends on your intention.
Intention is a noun.

It's like saying "is a knife considered sharp?", without saying what you are going to do with it.

[alancalverd]

There is a slight problem with BC's admirable spreadsheet.

Clearly the heat energy of a kilogram of hydrogen is not zero at 175K - that's just from the definition of the Kelvin scale!

And the boiling point of hydrogen is about 25K, so to be really fastidious we need to allow for the phase change.

Fortunately S_liq is pretty close to 14.4 so we can approximate the heat energy at 175K as around 14 x 175 = 2450. If you add that to BC's number you end up pretty close to mine.

As a nod to other pedants, yes, if you know S is a function of T you must integrate ∫SdT rather than just multiply by the final temperature.  And I've ignored the latent heat of melting and vaporisation too!

[Bored chemist]

As a nod to other pedants, yes, if you know S is a function of T you must integrate ∫SdT rather than just multiply by the final temperature.

So...
You are actually saying I was right all along...

An odd way to put it but... better late than never.

I should say that objects with higher temperature are some times treated like they have higher potential energy compared to the same/similar objects but at lower temperature.

Same object, yes. Similar object, no. The thermal energy (i.e. heat content) of a body of mass M, specific heat capacity S and temperature T  is MST.

Except that S varies with T.

[Bored chemist]

 If you put in the rest of the data and then add the 2450 that Alan talked about you get this graph of the error vs temperature.


error.jpg (19.79 kB . 481x289 - viewed 1927 times)

But... whatever... the fundamental issue remains.
You can't just multiply T by Cp because Cp isn't a constant, so you don't know which value to pick.

[alancalverd]

At 175K the (constant pressure) heat capacity of 1 Kg of H2 is 13.12 KJ  per kelvin

Which, multiplied by 175, gives you (to a first approximation) 2310 kJ, not 0.
Just because 175K is a bit chilly doesn't mean you can't extract some heat energy from your kilogram of hydrogen. You could get about 1300 kJ from it by constructing a Stirling engine with a liquid nitrogen cold source - practicable if pointless.

[Bored chemist]

At 175K the (constant pressure) heat capacity of 1 Kg of H2 is 13.12 KJ  per kelvin

Which, multiplied by 175, gives you (to a first approximation) 2310 kJ, not 0.
Just because 175K is a bit chilly doesn't mean you can't extract some heat energy from your kilogram of hydrogen. You could get about 1300 kJ from it by constructing a Stirling engine with a liquid nitrogen cold source - practicable if pointless.

Did you notice this bit?

then add the 2450 that Alan talked about

It's the bit where, even if we allow for that you are still wrong.
(and you seem to be repeating yourself.)

It would be interesting if we had data for other gases.

[hamdani yusuf (OP)]

Here is an attempt to explain temperature.

and thermal radiation

Are there something that you disagree with them?

[Bored chemist]

temp vid.jpg (144.11 kB . 1011x458 - viewed 1894 times)
It can't be a very good attempt; it shows the solid as full of springs, and then it ignores potential energy.

[alancalverd]

What's to explain? The caption statement is almost correct:  the definition of temperature is the average internal kinetic energy of a body. You can't explain a definition!

[Bored chemist]

Also, you don't supply thermal energy by applying a force.
You supply mechanical energy.
So, the first sentence of the vid is wrong.
And then it makes the flat out false assertion that rotation doesn't contribute to temperature.
It does.

Why does the video get so many things wrong?

[Eternal Student]

Hi.
    One of the issues with the the videos is that they are very long, so I've only skimmed through each one.
I also don't know who produced or created them, so there's no guide as to their reliability or accuracy.

    The first video looks like they have made some simplifications.
Their phrase " temperature is only a measure of the average translational k.e. of a molecule, not the rotational k.e."   cannot be taken in isolation from their mention of the equi-partition of energy among all the degrees of freedom.
    So if you have equi-partition of energy, then increasing the rotational k.e. will increase the translational k.e.   and vice versa,   or to say that another way,   it's a bit arbitrary to say that rotational k.e. of the molecules doesn't contribute to temperature.    Temperature is proportional to the energy in any one degree of freedom you choose to use.   By some vector algebra, it would be proportional to the overall translational k.e. if you prefer to consider that.
     
    I skipped through most of the second video.   They seemed to be suggesting ways to work with realistic thermal emissions that aren't exactly black bodies.   In the first few minutes there was some mention of "radiation" as one of the main mechanisms for heat transfer along with conduction and convection.  Did they define "thermal radiation" as radiation that arises from a body naturally whenever it's temperature is above 0 Kelvin - that would be OK as a definition.   I don't think they worried about explaining the mechanism for the creation of that radiation or any other fine details, just noted that a hot body would radiate and approximate a black body.

Best Wishes.

[hamdani yusuf (OP)]

It can't be a very good attempt; it shows the solid as full of springs, and then it ignores potential energy.

Perhaps the potential energy isn't counted as (doesn't contribute to) temperature.

[Bored chemist]

It can't be a very good attempt; it shows the solid as full of springs, and then it ignores potential energy.

Perhaps the potential energy isn't counted as (doesn't contribute to) temperature.

It is counted and does contribute.
Why choose to be wrong about that?

[Eternal Student]

Hi.

Perhaps the potential energy isn't counted as (doesn't contribute to) temperature.

    Do you mean you haven't actually spent your ( @hamdani yusuf )  own time watching those videos?   Their answer is in the video.

Best Wishes.

[hamdani yusuf (OP)]

It can't be a very good attempt; it shows the solid as full of springs, and then it ignores potential energy.

Perhaps the potential energy isn't counted as (doesn't contribute to) temperature.

It is counted and does contribute.
Why choose to be wrong about that?

Then the definition would be false.

What's to explain? The caption statement is almost correct:  the definition of temperature is the average internal kinetic energy of a body. You can't explain a definition!

[hamdani yusuf (OP)]

Hi.

Perhaps the potential energy isn't counted as (doesn't contribute to) temperature.

    Do you mean you haven't actually spent your ( @hamdani yusuf )  own time watching those videos?   Their answer is in the video.

Best Wishes.

You don't have to agree with everything presented in a video.