Temp.

[ThunderAeroI]

Its cold outside and I've been reading up on differnt types of tempreture scales on wikipedia and although the wiki is a great source of information I would like more.

I suppose we all know that 0 K is absolute zero where there is no entropy. From what I can tell the units of both K and C are at the same scale, but I am not clear on how they determined the units of the scale. It is simply that they took 273 C divded by 1 K and that probides the base scale?

Are there any tempreture scales that reflect actual heat engergy in their scale so that 20 units is twice the heat of 10 units?

Is there any estimate to what a maximum heat would look like?

It looks like there have been many scales thoughout time, and C seems to be the international standard, but since the scale of C is arbatrary I was curious if there was a scale that set out to make each unit of measurement reflect actual heat energy.

 

[Jadzia]

Fahrenheit first defined temperature rather awkwardly. He mixed chunks of ice with brine and found it went very cold. This was the lowest 'consistent' temperature he could make, and he called that zero Fahrenheit.

The hottest consistent temperature he could measure was his own body temperature. He called that 100 Fahrenheit. He interpolated these two marks on his mercury thermometer with 100 equal divisions, which became the Fahrenheit scale.

*

Celsius defined the centigrade scale (C) by the freezing and boiling points of pure water at sea level, as 0 and 100 Celsius.

Kelvin used the same calibration, but origin shifted so that zero was the lowest possible temperature. By this time, it was known that temperature related to the kinetics of particles of matter, and how these apply pressure/force when then impact a surface (container).

By measuring pressure, you can measure temperature through the gas law,

Pressure = Molar Density * Gas Constant * Temperature (Kelvins)

*

Are there any tempreture scales that reflect actual heat engergy in their scale so that 20 units is twice the heat of 10 units?

no, because it varies from substance to substance.

1 kg of water has more heat energy than 1kg of groundnut oil, even though both can be at the same temperature.

-- A mercury thermometer measures the temperature of the thermometer.

-- An IR thermometer reads radiation, which is indicative of temperature, not of actual heat energy.

 

[Chaos Descending]

Are there any tempreture scales that reflect actual heat engergy in their scale so that 20 units is twice the heat of 10 units?

Yes, the Kelvin and Rankine (an absolute scale calibrated in the same size units as the Fahrenheit scale) fit this criteria.

Any given substance at 20 Kelvins would have twice as much heat energy as the same substance at 10 Kelvins.

The hottest consistent temperature he could measure was his own body temperature. He called that 100 Fahrenheit.

He called it 96 Fahrenheit, actually. Later scientists re-calibrated the Fahrenheit scale to include the boiling point of water (they placed it exactly 180 degrees above the freezing point of water) which is why human body temperature is now judged to be around 98 Fahrenheit instead of the 96 measured by Mr. Fahrenheit.

Are there any tempreture scales that reflect actual heat engergy in their scale so that 20 units is twice the heat of 10 units?

no, because it varies from substance to substance.

1 kg of water has more heat energy than 1kg of groundnut oil, even though both can be at the same temperature.

Yes, true, but by comparing apples to apples (so to speak), 1kg of water at 20 Kelvins has double the heat energy of 1kg of water at 10 Kelvins.

An IR thermometer reads radiation, which is indicative of temperature, not of actual heat energy.

The IR emitted by a hot body is directly related to it's thermal temperature.

 

[cultcross]

Are there any tempreture scales that reflect actual heat engergy in their scale so that 20 units is twice the heat of 10 units?

Such a scale would be substance specific, because of Specific Heat Capacities. Simply put, the amount of energy input needed to raise the temperature of a substance - not all substances are created equal in that respect. For example, water is particularly good at cooling things because it has a high heat capacity - it can take a lot of heat energy from, say, a reactor, for a comparatively small rise in its temperature. Metals, by contrast, tend to have very low heat capacities - i.e. their temperatures go up much more easily with addition of much less heat energy.

Is there any estimate to what a maximum heat would look like?

There could be a theoretical 'maximum heat' because energy is a limited quantity in the universe, but in terms of energy input into a substance, there isn't a 'barrier' to hit like there is going the other way - you can keep adding energy until you run out of it.

It looks like there have been many scales thoughout time, and C seems to be the international standard,

In general conversation, arguably true - but Kelvin is the international scientific standard.

 

[Trekker4747]

As I recall, 0 Kelvin is "absolute zero" because it's the point where all atomic energy has stopped. Heat is energy and even when you touch a very cold railing in the Antarctic winter that railing still has "heat" -energy- to it in the grand scheme of things. That is, the atoms are still moving.

At 0 Kelvin all energy has been sapped out, the atoms have been forced as close together as they theoreticaly can be and they're not moving at all. In theory, 0 Kelvin is impossible to reach since energy transfers froma areas of high concentration to areas of low concentration, therefore, an object that reaches 0 Kelvin wouldn't be there for long as eventualy some surrounding energy will sap into the object raising it's temp over 0K.

Now, as I recall Fahrenheit used either his own or his spouse's temperature for the higher mark on his temperature scale and he called this "100." After a time, it turned out his wife (or whomever he measured) was running a slight fever that day so eventualy it came out that normal body temperature was 98.6.

I do kind of wonder why Fahrenheit didn't just use ice and boiling water to mark his scale -as is the 0 and 100 marks on Celsius- as those are both consistant and easy to reproduce temperatures instead of going with the brine-ice solution and the body temperature of a living being.

 

[Chaos Descending]

Fahrenheit used three points of reference, not two. The ammonium chloride and ice water mixture, the freezing point of water, and the human body temperature.

He initially set the human body temperature as 96 (not 100) so that it was 64 "ticks" from the freezing point of water, and it let him mark the graduations of his thermometer in even 1/2, 1/4, 1/8, 1/16 etc. fractions of the whole range from freezing to human body temperature.

It was only later that scientists "re-calibrated" the Fahrenheit scale so that the boiling point of water was exactly 180 "ticks" from the freezing point. It was on this "re-calibrated" Fahrenheit scale that body temperature wound up being about 98.6 Fahrenheit.

 

[Asbo Zaprudder]

Any given substance at 20 Kelvins would have twice as much heat energy as the same substance at 10 Kelvins.

Not quite true -- heat capacity is a function of temperature. The Debye model is a better approximation (but not perfect).

http://en.wikipedia.org/wiki/Debye_Theory

The IR emitted by a hot body is directly related to it's thermal temperature.

Actually the fourth power of absolute temperature according to the Stefan-Boltzmann Law.

http://en.wikipedia.org/wiki/Stefan's_law

 

[Chaos Descending]

Any given substance at 20 Kelvins would have twice as much heat energy as the same substance at 10 Kelvins.

Not quite true -- heat capacity is a function of temperature. The Debye model is a better approximation (but not perfect).

http://en.wikipedia.org/wiki/Debye_Theory

You have to admit that it's still pretty damn close. Close enough that for most applications you can thumb-rule it like I did.

I was trying not to go over the OP's head with the answers.

The IR emitted by a hot body is directly related to it's thermal temperature.

Actually the fourth power of absolute temperature according to the Stefan-Boltzmann Law.

http://en.wikipedia.org/wiki/Stefan%27s_law

Good clarification, but my point (that an exact account of the temperature can be obtained solely from the IR reading) is still very much intact.

 

[Asbo Zaprudder]

^ I take your point that you were providing first-order approximations, and I didn't mean it to seem like nitpicking. I find burrowing down into the details of physical law interesting.

In a similar vein, Drummerboy wasn't quite right in stating that all motion stops at 0K -- there is still zero-point vibration.

http://en.wikipedia.org/wiki/Zero-point_energy

 

[Chaos Descending]

^ I take your point that you were providing first-order approximations, and I didn't mean it to seem like nitpicking. I find burrowing down into the details of physical law interesting.

Fair enough!

In a similar vein, Drummerboy wasn't quite right in stating that all motion stops at 0K -- there is still zero-point vibration.

http://en.wikipedia.org/wiki/Zero-point_energy

Very good, excellent thing to point out.

Based on the Uncertainty Principle you can NEVER truly have zero motion.