Lecture 2,3,4 Flashcards
What does an inexact differential of a quantity mean?
The quantity is dependent on path
If work done is positive then the system _
Has had work done on it
What is a calorie?
The energy required to raise the temperature of 1g of water by 1 degrees celsius
Which of three quantities U, Q and W are path dependent?
Only Q and W
What is heat capacity?
The amount of energy required to raise the temperature of an object by a unit
What type of expansion will allow for the greatest amount of work done?
Reversible expansion. Think removing infinitesimally small weights one at a time and integrating, area under graph on pv diagram maximised
dU =
dQ + dW
delta U of the universe is always _
Zero
delta U of surroundings is equal to _
negative delta U of system = -Q-W
If three systems are in contact, and A,B and B,C are in thermal equilibrium, then _
A and C must be in thermal equalibrium
A thermometer works by _
Changing some quantity in response to heat flow: mercury changes volume, resistivity changes in thermocouple
What is the triple point of water?
The conditions under which water exists in equilibrium between all 3 states
Give the triple point conditions of water
273K 611.7Pa
What assumptions are made for an ideal gas?
Molecules occupy negligible space and have no interactions. They obey gas laws exactly
In wan der waals equation, what are the quantities a and b taking in to account?
a adjusts for interactions/forces of attraction
b adjusts for molecular volume
dW =
-p dV
For a reversible process, the external pressure -
Is equal to the internal pressure
For an isothermal gas expansion, delta U
Is always zero. Q = -W
What variables is enthalpy a function of?
Pressure and Temperature
For an ideal gas, enthalpy is a function of
Only temperature, not pressure
For an ideal gas undergoing a isothermal expansion, delta U _
Is equal to zero
For an ideal gas, internal energy is a function of
Temperature
What state variables is internal energy a function of?
Temperature and volume
