9: First Law of Thermodynamics Flashcards
Heat capacity, C
Specific heat capacity, c
The heat capacity, C, of a body is defined as the amount of thermal energy required to raise its temperature by 1K. [J K^-1]
The specific heat capacity, c, of a body is defined as the amount of thermal energy required to raise the temperature of 1kg by 1K. [J kg ^-1 K^-1]
Heat capacity equation
Q = mc▵T
R/s between thermal energy supplied and thermal energy gained
TE supplied = TE gained
Another formula for Q
Q = VIt = mc▵T
Power, P equation
P = E/t = Q/t
Specific latent heat, L
The specific latent heat, L, is defined as the thermal energy required to convert 1kg of a substance to another phase without a change in temperature. [J kg^-1]
Determination of latent heat of fusion, Lf
TE needed to melt ice = EE given out by heater
VIt = (m₁-m₂) Lf
Determination of latent heat of vaporization
TE from heater = Energy to change state + heat lost
(1) VIt = m Lv + h
(2) V’I’t = m’ Lv + h
∴ Lv = (VIt - V’I’t) / (m - m’)
Internal energy
Internal energy is the sum of a random distribution of kinetic (Ek) and potential energies (Ep) associated with the molecules of a system.
Intermolecular forces of an ideal gas is __________.
Negligible
Internal energy of an ideal gas =
sum of random KINETIC ENERGY (Ek) only
Equation of internal energy of monatomic ideal gas, U
3 expressions
U = 3/2pV = 3/2nRT = 3/2NkT
First Law of Thermodynamics
The increase in internal energy of a closed system is the sum of the heat supplied to the system a the work done on the system.
First Law of Thermodynamics equation
▵U = Q(to) + W(on)
Isothermal:
- no change in ________
- ___ = 0
- Graph?
- temperature
- ▵U = 0
- along isotherms
