## Why mole and kelvin are basic units?

 Quote by Khashishi The equipartition theorem states that the average energy in an accessible degree of freedom is 1/2 the temperature times the Boltzmann's constant. If we get rid of the Boltzmann's constant, we can just give temperature in energy units, which is a lot more natural and simple.
Interesting idea, but is it practical? Let's say I am in a biology lab and I need to measure the temperature of a blood sample. To have the thermometer read out in units of energy, it would have to be calibrated to the specific heat of this particular blood sample.

 Quote by the_emi_guy Interesting idea, but is it practical? Let's say I am in a biology lab and I need to measure the temperature of a blood sample. To have the thermometer read out in units of energy, it would have to be calibrated to the specific heat of this particular blood sample.
No specific knowledge of the specific heat of the sample is needed. The only difference is the unit of measurement. 1 K = 1.3806488*10^-23 J.
However, it isn't practical for everyday usage simply because of the huge difference in magnitude. Room temperature is on the order of 10^-20 joules.

Both Boltzmann's constant and Avogadro's number are used to connect the microscopic scale to human scale, and therefore have similar values. We could get rid of kB and just express temperatures in terms of J/mol, and the scales would be reasonable.
 Khashishi, Forgive me, I am still unclear on this. I thought that heat capacity was the conversion from energy to temperature. As you mentioned earlier, the constant of proportionality between E and T is 1/2(K) per degree of freedom. For simple substances (monatomic gasses, perhaps plasmas) we know how many degrees of freedom are involved so we can convert freely between E and T. But how many degrees of freedom should we assign to a blood sample?

Mentor
 Quote by Khashishi Both Boltzmann's constant and Avogadro's number are used to connect the microscopic scale to human scale, and therefore have similar values. We could get rid of kB and just express temperatures in terms of J/mol, and the scales would be reasonable.
No, we couldn't. Molar energy loses something in translation. Different substances at the same temperature do not necessarily have the same molar energy. Another problem is that the relation between energy and temperature is not linear.

 Quote by Khashishi The equipartition theorem states that the average energy in an accessible degree of freedom is 1/2 the temperature times the Boltzmann's constant. If we get rid of the Boltzmann's constant, we can just give temperature in energy units, which is a lot more natural and simple.
The equipartition theorem is an idealization. It works great for ideal gases. It is not valid for real gases. It doesn't account for phase transitions, it doesn't account for the fact that specific heat is not constant for real substances, and it doesn't work for solids at low temperatures.
 I thought I was clear. I was not suggesting to get rid of temperature altogether and just use internal energy. I was suggesting using energy units to measure temperature. It's still temperature, just with a different unit.
 I am a bit unclear about temperature. What is it actually? I thought its the average energy of the molecules/atoms of a compound. But if it is that then we can write temperature in joules but we don't!

 Quote by jd12345 I am a bit unclear about temperature. What is it actually? I thought its the average energy of the molecules/atoms of a compound. But if it is that then we can write temperature in joules but we don't!
No.

For example, consider 1 liter of argon gas, and 1 liter of chlorine gas, both at the same temperature. The chlorine gas will contain about twice the thermal energy in Joules as the argon.

Khashishi -
Would those two bottles of gas be at the same temperature in your proposed units?