Thermodynamics Flashcards
zeroth law of thermodynamics .
states that objects are in thermal equilibrium when they are at the same temperature.
Temperature
a qualitative measure of how hot or cold an object is; qualitatively.
Thermal expansion
describes how a substance changes in length or volume.
Thermodynamic system
is the portion of the universe that we are interested in observing, where as the surroundings include everything that is not part of the system.
isolated systems
do not exchange matter or energy with the surroundings
closed systems
exchange energy but not matter with their surroundings
open systems
exchange both energy and matter with their surroundings
state functions
are pathway independent are not themselves defined by a process. Pressure, density, temperature, volume, enthalpy, internal energy, gibbs free energy, and entropy are all state functions.
Process functions
describe the pathway from one equilibrium state to another. work and heat are process functions.
First law of thermodynamics
statement of conservation of energy: the total energy in the universe can never decrease or increase .
ΔU = Q - W
ΔU is the change in the systems’ internal energy
Q is the energy transferred into the system as heat
W is the work done by the system
for a closed system, total internal energy is equal to …
the heat flow into system minus the work done by the system
Heat
a process of energy transfer between two objects at different temperatures that occur until the two objects come into thermal equilibrium
Specific heat
the amount of energy necessary to raise one gram of a substance by one degree Celsius or one kelvin
specific heat of water
1 cal/g k
Heat of transformation
during a phase change, heat energy causes changes in the particles’ potential energy and energy distribution (entropy), but not kinetic energy. Therefore, there is no change in temperature.
isothermal processes,
the temperature is constant, and the change in internal energy is therefore 0
adiabatic processes
no heat is exchange
isobaric processes
the pressure is held constant
isovolumetric processes
the volume is held constant and the work done by or on the system is zero
second law of thermodynamics
states that in a closed system (up to and including the entire universe), energy will spontaneously and irreversibly go from being localized to being spread out (dispersed).
ΔS universe = ΔS system + surroundings > 0
Entropy
is a measure of how much energy has spread out or how spread out energy has become .
ΔS = Qrev/T . Qrev is heat gained or lost in a reversible reaction .
As the number of micro-states increases, the potential energy of a molecule…
is distributed over that larger number of micro-states, increasing entropy
Every natural process is ultimately…
irreversible, under highly controlled conditions, certain equilibrium processes such as phase changes can be treated as essentially reversible.
F= how many C
9/5C+32
K = how many C
C+273
thermal expansion equation
ΔL = αLΔT ΔL is the change in length, α is the coefficient for linear expansion, L is original length, ΔT is the change in temperature
Volume expansion equation
ΔV = βVΔT . β is the coefficient of volumetric expansion, equals 3 alphas .
Heat gained or lost (with temp change)
q = mcΔT
m is the mass, c is the specific heat of the substance, and ΔT change in heat
Heat gained or lost (phase change)
q=mL . m is mass L is heat transformation or latent heat
