Thermodynamics Flashcards
Define a Thermodynamic System
The particular thing or part of the physical universe that we choose to study
Define Boundary
The real or imaginary separation between the system and the rest of the universe. If clearly defined the system can exchange energy and matter.
Define Surroundings
The part of the universe that is outside the system (everything else)
Define Universe
The system and surroundings
Define Open System
Can exchange both energy and matter with the surroundings (both energy and matter can cross the boundary)
Define a closed system
Can exchange energy, but not matter, with the surroundings
Define an isolated system
Cannot exchange energy or matter with the surroundings
Define State variables (aka state variables)
Describes the conditions of a system. Does not depend on how that state was achieved (path independent).
Give some examples of state variables
Examples: temperature, pressure, volume, density, mass, and concentration.
Define Intensive Variables
Independent of the size of the system (size does not matter)
Define extensive variable
Dependant on size of the system (changes with size and only size, not volume)
What are some examples of intensive variables?
Pressure, temperature, density, number of moles, molar mass, and concentration.
What are some examples of extensive variables?
Volume, mass, and energy.
How do you change extensive to intensive and vise versa?
Ext / Int = Ext
Ext / Ext = Int
You cannot change an intensive variable to extensive.
How do you change extensive to intensive and vise versa?
Ext / Int = Ext
Ext / Ext = Int
You cannot change an intensive variable to extensive.
Define Equilibrium
When properties of a system in a certain state are independent of time (stable).
What is the Ideal Gas Law
Describes the relationship among thermodynamic state variables of ideal gases at equilibrium.
PV =nRT
What is an ideal gas?
Non-interacting
Point particles
In random motion
Undergoing perfectly elastic conditions
What does it mean to be non-interacting?
Do not exert forces on each other (other than collisions)
What is a point particle?
Particles that have no volume
What does it mean to have a perfectly elastic collision?
Energy is conserved
What is the First Law of Thermodynamics?
Change in E = q + w
How is energy transferred?
Heat (q) and/or work (w)
How is energy transferred?
Heat (q) and/or work (w)
How do you calculate work? Aka what is the formula?
W = -Pext x change in volume
How does q become - or + ?
When heat is absorbed (q+), and when lost (q-)
When is work + and - ?
When work is done ON the system W > 0
When work is done BY the system W < 0
What is the difference between state functions and path variables ?
State functions DO NOT depend on the path.
Path variables DO depend on the path (ex: work and heat)
What does isothermal mean?
Temperature remains constant (Tf = Ti)
What does it mean to have an ideal gas in a closed system?
T is directly proportional to E (change in T = change in E)
How do you find out work with a P vs. V graph?
By calculating the area under the curve. (May have to integrate with curve)
