Can the weight of heat be accurately measured in such small increments?

  • Thread starter Thread starter alba
  • Start date Start date
  • Tags Tags
    Heat Weight
AI Thread Summary
The discussion centers on the measurement of mass increase in gold due to temperature rise, specifically questioning the calculation that a 10°C increase results in a mass increase of 1.4 * 10^-14 kg. Participants clarify that the energy added to the gold can be calculated using its specific heat capacity, which results in an energy increase of 1260 J for 1 kg of gold. There is confusion regarding the application of E=hf and the relevance of photon energy to mass increase, with assertions that the relationship between energy and mass should be derived from E=mc^2 instead. The conversation emphasizes the importance of using correct physical units and understanding the specific heat capacity to accurately determine energy changes. Overall, the discussion highlights the complexities of thermodynamics and mass-energy equivalence in practical scenarios.
alba
Messages
140
Reaction score
4
I read that if the temperature of 1 Kg of gold rises by 10°C its mass increases by 1.4 * 10^-14 kg.
Can you please explain how you get such value from E= mc^2?
I think the increase corresponds to E = h f =1.53*10*10^36 and since
1 kg has 1.1*10^30 electrons, each one gets 1.4*10*6 h
but
10 degrees correspond to energy E = h f = 2.8*10^11 h)

so shouldn't the increase of energy be 2.29*10 ^41 h?

Can you also tell what instrument can measure the weight o 10^-14 Kg and what is the minimal weight that can be detected?
 
Science news on Phys.org
It is completely unclear what you are trying to do. E=hf is the energy content of a photon and has absolutely nothing to do with the mass increase of the gold. You need to figure out how much energy needs to be added and compute the corresponding mass increase.
 
Orodruin said:
It is completely unclear what you are trying to do. E=hf is the energy content of a photon and has absolutely nothing to do with the mass increase of the gold. You need to figure out how much energy needs to be added and compute the corresponding mass increase.
E = 1.4*10-14* 9*10^16 = 12 = 1260 J
The energy of a joule can be expressed in many ways, in eV or in h*Herz 1260 /h = 1.9*10 ^36
what is the problem? that is the energy added, I cannot figure out how that relates to T = +10*C

Any ideas?
 
alba said:
The energy of a joule can be expressed in many ways, in eV or in h*Herz 1260 /h = 1.9*10 ^36
what is the problem?
Which units you use are unrelated to how you solve the problem. There is no point in using E=hf here.

alba said:
E = 1.4*10-14* 9*10^16 = 12 = 1260 J
Just putting numbers is not a very good way to present a solution. First write down the physical relation you are using, then write down what numbers you are putting in (including units!).

alba said:
that is the energy added, I cannot figure out how that relates to T = +10*C
The energy added must depend on the temperature increase. If yours does not, it is wrong.
 
To understand how to calculate the "heat" energy required to raise the temperature of something, read this: Specific Heat
 
Thank you very much for the links, so:
c for gold is 0.126 J/gmK 1000g, therefore 1000g*10 K makes 1260 J (1.5*10^36 hv), right?
 
alba said:
c for gold is 0.126 J/gmK 1000g, therefore 1000g*10 K makes 1260 J
1260 J looks good to me.

alba said:
(1.5*10^36 hv)
What's this?
 
Doc Al said:
1260 J looks good to me.
What's this?
Is it so weird to refer to energy by Hz? 1 J equals 1.5*10^33 h/s, right?

Can you tell me if the weight increase is just deduced from the formula, or if it is (and to what precison) confirmed my measurement?
 
  • #10
alba said:
Is it so weird to refer to energy by Hz?

It simply does not make any sense. You could do this by using units of ##\hbar## but this is normally done in particle physics and this is not.
Also, in your answer you are referring to ##hf##. This makes no sense at all unless you specify what ##f## is.
 
  • Like
Likes alba
  • #11
alba said:
I read that if the temperature of 1 Kg of gold rises by 10°C its mass increases by 1.4 * 10^-14 kg.
Can you please explain how you get such value from E= mc^2?
alba said:
c for gold is 0.126 J/gmK 1000g, therefore 1000g*10 K makes 1260 J
So now you know E (or more precisely, the amount by which the E of the gold increases when its temperature increases by 10°C). Now, what m does this give you?
 
  • #12
Orodruin said:
This makes no sense at all unless you specify what ##f## is.
You must have missed that, in my first post I specified
f =1.53*10*10^36
 
  • #13
alba said:
You must have missed that, in my first post I specified
This is completely besides the point. You cannot just arbitrarily select a frequency.

Apart from that, your "frequency" is not a frequency, it is a number. A number is meaningless without the appropriate physical units.
 
Back
Top