Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: castromatic on June 27, 2018, 06:24:43 AM
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(they both start at 10 degrees celsius this is all hypothetical lol)
BP of gold = 2700 degrees c
BP of water = 100 degrees c
specific heat of gold = 0.126
specific heat of water = 4.184
initial temperature = 10 degrees for both
energy of gold = (1g)(0.126j/gc)(2700c-10c)
=338.94 Joules
energy of water = (1g)(4.184j/gc)(100c-10c)
=376.56 Joules
Maybe I'm overthinking it ? Does this mean I can raise gold to its boiling point more easily than doing the same to water? I'm confused
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How easy is it to heat anything to 100C rather than 2700C?
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The heat of fusion of gold was forgotten.
A constant heat capacity is seriously inaccurate here: the temperature varies too much for that. Such a computation demands to integrate the variable heat capacity over the temperature range, or easier, to find a table of the enthalpy contents as a function of the temperature. Available for elements like gold, and called "steam table" for water.
In the inaccurate computation, the temperature difference and the heat capacities happen to compensate. This is because gold atoms are heavy, so there are fewer to store energy than in water. Also, water molecules attract an other, but this bond gets more and more broken by heat in the liquid, which increases the heat capacity. A different element like carbon would not give the same result as water and gold.
Just as a side note, degrees Celsius are written °C (° and big C), and the proper unit for temperature differences is the Kelvin, written big K. Don't forget neither to write all units, it helps to avoid mistakes. While chemists like grams, the SI unit is the kg; as well, you may often find calories in older texts, instead of joule.
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Just as a side note, degrees Celsius are written °C (° and big C), and the proper unit for temperature differences is the Kelvin, written big K.
I was taught that you didn't need the degrees part as it was superfluous. I think it was when we called it the centigrade scale that we would say degree's Centigrade. We don't say 'degrees Kelvin' we just say Kelvin.... as with Celsius, we just say 100 Celsius not 100 degrees Celsius. That's what we were taught - but Wiki seems to not mention it and says it's degrees Celsius - which goes against what I was taught at school.
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Yeah, I was taught that too. That by definition, Centigrade (or maybe its Celsius) is dimensionless, you don't need to write "°" with temperatures in C. Which is great, because "°" isn't always availible in all fonts. However, it seems like "° C" has taken over the conventions for writing.
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Here's still an other source, the (1991!) CRC Handbook of Chemistry and Physics.
It tells "degree Celsius" and "°C", but as opposed to what I had written,
"The SI unit of Celsius temperature interval is the degree Celsius, °C, which is equal to the Kelvin, K".
Wiki too tells "degree Celsius" and "°C"
https://en.wikipedia.org/wiki/Celsius
I find the ° paramount in °C because it's the only difference with the Coulomb C.
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Indeed, I was taught the opposite - ° is needed for centigrade but not for kelvin.
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IUPAC specifies the use of the ° symbol with Celsius but not Kelvin.
https://goldbook.iupac.org/html/C/C00928.html
The reason is because Kelvin is an absolute temperature scale and Celsius is not. A Kelvin therefore is an actual unit of temperature.
You may read more here: https://sciencenotes.org/why-there-is-no-degree-in-kelvin-temperature/
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I was taught °C and K, but that was somewhere around K–Pg extinction event.