THERMODYNAMICS Flashcards
what is thermodynamics
the study of energy and its relationship to chemical systems
what two things are needed for a thermodynamic system
a system and its surroundings
define system
object that experiences a thermodynamic transformation.
define surroundings
Any part of the universe that is in direct contact with the system is its surroundings
what are the three types of system
open, closed, and isolated
what occurs in an open system
heat transfer
mass transfer
what occurs in a closed system
heat transfer
no mass transfer
what occurs in an isolated system
no heat or mass transfer
define work in a thermodynamic context
any energy transfer that is not heat
what is internal energy also called and how can we calculate this simply
average total mechanical energy (kinetic + potential) of the particles that make up the system.
what are the three types of heat transfer
conduction, convection, and radiation
what is heat
transfer of energy from a warmer body to a cooler body
how does conduction carry out thermal energy transfer
thermal energy transfer via molecular collisions, requires direct physical contact
what is required for the particles in conduction to transfer thermal energy
direct physical contact
how do molecule collisions in conduction carry out thermal energy transfer
higher energy molecules of one system transferring some of their energy to the lower energy molecules of the other system via molecular collisions
what is convection
thermal energy transfer via fluid movements
how does convection transfer thermal energy
Warm fluid moves in the direction of cooler fluid due to differences in pressure or density
what is radiation
Radiation is thermal energy transfer via electromagnetic waves
what does the first law of thermodynamics state
energy of the system and its surroundings is always conserved
what is Q
Q = Quantity of heat supplied to the system by its surroundings
What is W
W = Net work done by the system
what happens in the change in internal energy equation when work is done on the system
Work done on system = + W
what happens in the change in internal energy equation when work is done by the system
Work done by system = - W
what happens in the change in internal energy equation when heat is added to a system
Heat added to system = +Q
what happens in the change in internal energy equation when heat is given off by a system
- Heat given off by system = -Q
how do you calculate change in internal energy
Change in U = +/-Q +/- W
what is the second law of thermodynamics trying to prove
heat cannot be completely changed to work in a cycle-like process
what does the second law of thermodynamics show about heat transfer direction
allows for the determination of the preferred direction of a given transformation – for example, we know that heat flows from a hot source to a cold source
what is the symbol and unit for internal energy
U
Joule
what is the symbol and unit for temperature
T
Kelvin
what is the symbol and unit for pressure
P
Pascal
what is the symbol and unit for volume
V
m^3
what is the symbol and unit for enthalpy
H
kJ mol-1
what is the symbol and unit for entropy
S
JK mol^-1 (joules per kelvin)
what is the symbol and unit for gibbs free energy
G
kJ mol-1
what is internal energy
collective energy of molecules
in a system with constant volume and no work what is the internal energy the same as
heat
for internal energy to be equated to heat, what is the condition
- constant volume
- no work done
what is temperature an example of
thermodynamic property
in fluid, temperature is directly proportional to what
the translational kinetic energy of its molecules
in gas, what happens if the translation energy per mole of gas increases
greater the temperature
greater pressure
how do you convert from Celsius to Kelvin
0 celsius = 273.15K
+ 273.15 to whatever required
then every 1kelvin = 1Celsius
convert 30 celsius water to kelvin
273.15 + 30
= 303.15 kelvin
if a pot of water is at 303.15 and you increase it by 1 celsius, what is the water temperature in kelvin
304.15 kelvin
31°C
what is enthalpy’s basic law
H = internal energy + (pressure x volume)
what is standard enthalpy of formation
enthalpy to make one mole of compound from elements
what is enthalpy used to approximate
heat
what is the equation for change in enthalpy
Products - reactants
what does hess’ law state
when adding reactions, their enthalpies can be added because enthalpy is a state function
what is an exothermic value in enthalpy
-ΔH
enthalpy of products is less than enthalpy of reactants
what is an endothermic value in enthalpy
+ΔH
enthalpy of products is more than enthalpy of reactants
what is entropy
degree of disorder in a system
what state of matter has the highest entropy
gas
how does entropy increase
solid to a liquid to a gas
why does gas have a higher entropy than water
gas molecules exhibit an increased random motion of movement
what does gibbs free energy determine
if a reaction is spontaneous or not, or if the reaction is at equilibrium
what is the equation for gibbs free energy
∆G = ΔH - (T x ΔS)
what happens if ∆G is less than 0 [at constant pressure]
spontaneous
what happens if ∆G is 0
in a state of equilibrium
what happens if ∆G is more than 0 [at constant pressure]
not spontaneous
