4. Thermodynamics Flashcards
what do open systems exchange
both mass and heat/energy with their surroundings
what do closed systems exchange
heat and energy but not mass
what do isolated systems exchange
not heat/energy or mass
internal energy is the average total of what
average total mechanical energy (kinetic + potential) of the particles that make up the system
what is conduction
what does it require
thermal energy transfer via molecular collisions
requires direct physical contact and process involves higher energy molecules of one system transferring some of their energy to lower energy molecules of the other system via molecular collisions
what is convection
thermal energy transfer via fluid movements
why do warm fluids move in direction of cooler fluid
due to differences in pressure or density
what is radiation
thermal energy transfer via electromagnetic waves
what is the first law
energy of system and its surroundings is always conserved
what is the equation for the first law
change in internal energy = quantity of heat supplied to system by surroundings + net work done by system
U = Q + W
what is + W
work done on system
what is -W
work done by system
what is +Q
heat added to system
what is -Q
heat given off by system
what is the second law
heat cannot by completely changed to work in a cycle-like process
what is the symbol and SI unit for internal energy
U - joule
what is the symbol and SI unit for temperature
T = kelvin
what is the symbol and SI unit for pressure
P = pascal
what is the symbol and SI unit for volume
V = m^3
what is the symbol and SI unit for enthalpy
H = kJmol^-1
what is the symbol and SI unit for entropy
S = JK^-1mol^-1
what is the symbol and SI unit for gibbs energy
G = kJmol^-1
for a reaction in a system with constant volume is work done
no work of any kind is done and the change in internal energy is equal to the heat
for a fluid temperature is directly proportional to what
translational kinetic energy of molecules
the greater the random translational energy per mole of gas what happens to temp
greater the temp
how do you convert Celsius to kelvin
add 273.15
increase of 1K is equal to increase of how many celsius
increase of 1 degree
what is the enthalpy equation
H = U + PV
what is the change in enthalpy equation
change in reaction enthalpy = change in product enthalpy - change in reactant enthalpy
what does hess law state
adding reactions then their enthalpies can be added because enthalpy is a state function
what is an exothermic reaction
system releases heat to surroundings
what change in H does exothermic reactions have and why
-H
enthalpy of products is lower than the enthalpy of reactants of system
what change in H does endothermic reactions have and why
+H
enthalpy of products is higher than the enthalpy of the reactants of the system
what happens in an endothermic reaction
reactants absorb heat from surroundings
what does entropy measure
degree of disorder in a system
as you go from solid to liquid to gas what happens to the entropy
increases entropy
what is the gibb free energy equation
change in G = change in H - T x change in S
if H and S are both + what will G be
positive at low temp
negative at high temp
if H is + and S is - what will G be
positive at all temp
if H is - and S is + what will G be
negative at all temp
if H and S are both - what will G be
negative at low temp
positive at high temp
