[Annieclo]

This a Meat thermometer , has metal skewer , there are no instructions. and look on Makers site , No trace of this product?
Answer:The metal skewer is to make a hole in meat etc to enable the thermometer to be inserted more easily. You don't put the thermometer IN the microwave - you simply use it to check the temperature of the foods you have cooked in there.

Absolutely! I Use it to make sure that the center of the meat is at a temperature that renders it safe. In particular useful for grilled chicken thighs and hamburgers.
By doing this I have found that chicken is moist but safe, same for hamburgers.
It's good for those who try different meat recipes.

[hamdani yusuf (OP)]

Another important factor in thermal radiation is emissivity. Is radiation by an object with extremely low emissivity considered thermal?

[Bored chemist]

Another important factor in thermal radiation is emissivity. Is radiation by an object with extremely low emissivity considered thermal?

It still depends.

[alancalverd]

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.

[alancalverd]

Take a continuous spectrum, but has flat distribution (up to certain frequency), instead of black body radiation. Is it considered thermal?

If it is due to heat, yes.

[Bored chemist]

Take a continuous spectrum, but has flat distribution (up to certain frequency), instead of black body radiation. Is it considered thermal?

If it is due to heat, yes.

But heat wouldn't give a flat spectrum so it can't be thermal- though it might be close enough.


I think we have an example of the "all Dalmatians are dogs, but not all dogs are Dalmatians"  issue here.

A thermal spectrum is a continuum.

All thermal spectra are continuous, but not all continuous spectra are thermal.

[Bored chemist]

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.

[hamdani yusuf (OP)]

Take a continuous spectrum, but has flat distribution (up to certain frequency), instead of black body radiation. Is it considered thermal?

If it is due to heat, yes.

Sunlight is filtered to produce a narrow spectrum radiation. Is it considered thermal?

[hamdani yusuf (OP)]

All thermal spectra are continuous, but not all continuous spectra are thermal.

Sunlight is filtered by a band stop filter which absorbs a narrow spectrum radiation at 500 nm wavelength. Is it still considered a thermal spectrum even though it's no longer continuous?

[alancalverd]

The source was mostly thermal in both cases. The product is a narrow spectrum or a continuous spectrum with a bit missing.

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.

But at any particular value of T  (except at critical temperatures between phase changes) the heat content is MST. IN a phase change it is T(ΣM_xS_x).

[Bored chemist]

But at any particular value of T  (except at critical temperatures between phase changes) the heat content is MST. IN a phase change it is T(ΣMxSx).

No
As discussed earlier.
If there's not enough thermal energy to excite vibrations then the vibrational part of the heat capacity is zero, but at higher temperatures it's significant.
So S varies with T even though there is no phase change.

https://www.engineersedge.com/thermodynamics/specific_heat_common_gases__13695.htm

[Bored chemist]

Take a continuous spectrum, but has flat distribution (up to certain frequency), instead of black body radiation. Is it considered thermal?

If it is due to heat, yes.

Sunlight is filtered to produce a narrow spectrum radiation. Is it considered thermal?

Another important factor in thermal radiation is emissivity. Is radiation by an object with extremely low emissivity considered thermal?

It still depends.

All thermal spectra are continuous, but not all continuous spectra are thermal.

Sunlight is filtered by a band stop filter which absorbs a narrow spectrum radiation at 500 nm wavelength. Is it still considered a thermal spectrum even though it's no longer continuous?

Another important factor in thermal radiation is emissivity. Is radiation by an object with extremely low emissivity considered thermal?

It still depends.

[hamdani yusuf (OP)]

It still depends.

Is it supposed to be an answer?
Let's agree that it depends on something.
What does it depend on?

[Bored chemist]

Is it supposed to be an answer?

It's the truth.

Let's agree that it depends on something.

Good

What does it depend on?

I already told you twice.
Did you not understand?

[hamdani yusuf (OP)]

I already told you twice.

Which one?

[alancalverd]

No

I think you mean yes.  Everyone knows that S varies with T, but at any particular value of T, S will have a value.

[Bored chemist]

No

I think you mean yes.  Everyone knows that S varies with T, but at any particular value of T, S will have a value.

Yes, and the clever ones know that you need to integrate the energy added over the temperature rise.

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]

There's data here for hydrogen
https://www.engineeringtoolbox.com/hydrogen-d_976.html
And I copied some of it into a spreadsheet
The first row says
175     13.12

At 175K the (constant pressure) heat capacity of 1 Kg of H2 is 13.12 KJ  per kelvin
So, raising the temperature of that 1 Kg to 176 K would take 13.12 KJ
And that's where Alan gets his wrong number from.


There's no data in the table for 176K, or 177K.
But there's data for 200K (where Cp is 13.53) and we can assume it's close to a linear change with temperature.

So, if we want to heat the gas to 200K we multiply the average heat capacity by the temperature rise.

And we can keep on doing that, and add up the heat at each step to get the total heat added to the gas as a function of temperature.
I'm lazy enough to use a spreadsheet to do that, and here's the result. I have included Alan's number - the product of the heat capacity and the temperature, for comparison. (I'm talking about 1Kg of H2 so the mass (M)  is 1.


H2 Cp.JPG (106.35 kB . 476x685 - viewed 1711 times)

[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

[hamdani yusuf (OP)]

No

I think you mean yes.  Everyone knows that S varies with T, but at any particular value of T, S will have a value.

Yes, and the clever ones know that you need to integrate the energy added over the temperature rise.

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.

Alan's previous post is more like using average value of S in the range of temperature under consideration. No multiplication by zero is involved.