Introduction and some key terms Ch1-3 Flashcards
WIA function of state?
A function of state is any physical quantity that has a well defined value for each equilibrium state.
WIA EXTENSIVE function of state. Give examples.
Extensive = Proportional to system size.
Ex = Energy, E, Volume, V
WIA INTENSIVE funtion of state?
Give examples.
Intensive = Independent of size of system.
Ex = pressure, P, Temperature, T
Are microscopic properties such as particle velocities considered functions of state?
NO, neither is work done or heat transferred as they depend on the process and not just the states.
What is the Zero-th law of Thermodynamics?
Zero-th law: If 2 systems are in thermal equilibrium with a third system, then the 2 systems are in thermal equilibrium with each other
Although Ideal gases are impossible, how could we experimentally achieve them?
Speciall case: Use 1 mole of a very dilute gas.
Ideal Gas eq.
pV = nRT
Functions of states are not all independent (otherwise there would be no theory), hence there are equations of state
The most important equation of state is pV=nRT
Functions of states are not all independent (otherwise there would be no theory), hence there are equations of state
The most important equation of state is pV=nRT
3 functions of states, p,V,T, knowing 2 fixes the 3rd, hence ‘2 degrees of freedom’, e.g. you might see T(p,V) or E(p,V)
What is the area under a P/V graph equal to?
Area under P/V curve = Work
(mechanical work)
What is the equation of mechanical work in terms of pressure and volume?
W = p x V
(from W = Fd, F= PxA –> W = PxAxL = pxV)
dw = p x dV
OR
dw = dp x V
Define Adiathermal
No heat exchange allowed- thermally isolated.
dQ = 0 «—- important-
dE = dQ + dW –> dq =0 hence dE = dW
Adiabatic also used to mean Adiathermal, but now is taken to mean isentropic..
Define Isobaric
At constant Pressure
Define Isovolumic
At constant volume
Define Phase
Region within a system that is homogeneous(the same) and with well defined boundaries.
What is the First Law of Thermodynamics? (def)
The first law States that the Internal energy Change of a system, dE, is the sum of the Work done on the system dW and the Heat supplied to the system dQ.
What is first Law of Thermodynamics (eq)
E = Q + W
If a system has done work on its surroundings, then the system has done NEGATIVE work- when an object does work it LOSES energy.
Why is dW = -p dV?
If a system has a reducing volume , then you are doing work on the system(work done on system, dW, is positive). However, dV is negative, so for dW to be positive the negative sign is needed, dW = -p dV (- x - = positive). This works the other way, if the Volume is increasing, the system is doing work on the environment, hence the work done on the system is negative (dW is -ve), so for dw to be negative-» must have dW = - p dV (- x+ = -).
T/F? dE = -p dV + dQ?
T
T/F? dQ = dE + p dV
T
If Energy is a function of Temperature and Volume- E(T, V), how could you express dE?
What is the equation of Heat capacity? What do Cp and Cv refer to?
C = dQ/dT
Cp = Heat capacity at const. pressure PER MOL
Cv = Heat capacity at const. Volume PER MOL
Derive the heat Capacities for const. Volume and for const. pressure using the First law of Thermodynamics.
Hint 1: Use dE = dW + dQ.
Hint 2: Energy is a function of Temp and Vol, E(T, V).
Hint 3: dW = - p dV, C = dQ/dT
How do Specific Heat Capacity and Heat Capacity differ. What is the difference between Cp and Cv?
Heat Capacity is the amount of thermal energy needed to change a substance’s temperature by 1 K (or degree). Specific heat capacity is the amount of energy required to change a substance’s temperature by 1 K per unit kilogram.
SHC = HC/m
Cp-Cv = R/n Cp and Cv are molar heat capacities! Don’t forget this!
n*(Cp - Cv) = R
