Principles of Chemistry I - Test #4: Thermodynamics

kinetic energy

-energy that something has because it is moving

Kinetic energy depends on a particle's...

mass and velocity

translation

3D movement of particles

movement of particles in a solid

vibration or rotation

potential energy

energy something has as a result of its position

types of potential energy

structural or positional

examples of potential energy

gravitational, electrostatic, chemical bond energy

-E =

q+w

internal energy

sum of all the individual energies of nanoscale particles in a system

internal energy depends on...

temperature, type, and number of particles

higher T =

higher energy

Joule

1 kg m^2/s^2

calorie

original energy unit, 4.184 J

calorie definition

energy required to heat one gram of water one degree celsius

system

the region of the universe we are studying

surroundings

everything else, separated from the system by a boundary

open system

exchanges both energy and matter with the surroundings

closed system

exchanges energy but mot matter with the surroundings

isolated system

neither energy nor matter is exchanged between the system and surroundings

open system example

a glass of soda

closed system example

a unopened can of soda

isolated system example

capped thermos bottle

equation for calculating thermodynamic change

deltaE = Efinal -Einitial

state variable

depends only on the state of the system and is independent of how it got there

path variable

depends on how the state was reached

heat (q)

the energy associated with the translation, rotation, and vibration of molecules

magnitude of delta T depends on...

q

molar heat capacity (C)

accounts for the identity of a material and is intrinsic

molar heat capacity synonym

heat capacity

heat capacity equation

C=q/n deltaT

specific heat capacity

quantity of heat required to raise the temperature of one gram of a substance by one degree K

specific heat synonym

specific heat

work (w)

energy used to move an object against an opposing force

work=

force x displacement

work units

N*m

expansion work

w= -Pext x deltaVsystem

First Law of thermodynamics

deltaEsys = qsys + wsys
qsurrounding = -qsystem

automobile engine

some heat is lost while doing expansion work

automobile engine equation

deltaEstove = qengine + wengine

gas stove

all energy is converted into heat

gas stove equation

deltaEstove = qstove

calorimetry

device that measures heat flow in a chemical reaction

calorimetry equation

qsys = qcalorimeter + qchemical = 0

constant pressure calorimeter

-most common way to measure heat flow
-used in most labs
-explains biological systems
-open system

constant volume calorimeter

-bomb calorimeter used to counteract large pressure increase
-closed system

enthalpy equation

H = E + PV
deltaH = deltaE + PdeltaV

heat of formation

heat required to produce of a single product from standard elements in standard condition

Hess's Law

the enthalpy change for any process s the sum of the enthalpy changes for any set of steps leading up to it

enthalpy is related to

intermolecular force strength

lattice energy

the energy required to separate one mole of an ionic solid

exothermic reactions tend to favor

products

free energy

energy we can use to do work

energy is more likely to spread...

over many particles rather than a few

entropy

a measure of dispersed energy of a system

how can we disperse energy/matter?

spread something into a larger volume or allow two items to reach thermal equilibrium

mixing of miscible substances

spontaneous

most probable mixing pattern of particles

has the most uniform distribution of particles thru the volume the particles occupy

W

number of energy equivalent arrangements of particles

entropy is proportional to...

number of possible arrangements

Boltzmann equation for entropy

S = k ln(W)

accessible microstates

probable number of arrangements of particles at a particular T

third law of thermodynamics

entropy of a pure, perfect crystal is zero at O K

standard molar entropy

entropy of one mole of a substance at P= 1 barr and T=25 C

which phase of matter has the greatest entropy

gases

quantum theory of entropy

energy levels for gas motion get closer together when the volume expands, more energy levels become accessible at a given T, E will disperse more over these levels

when a processes product favored?

when energy is dispersed from few to many levels

Carnot entropy equation

S= Sf-Si = qrev/T

reversible process

can be reversed by a slight change in condition

entropy of solids

very small as particles are essentially fixed

entropy of liquids

moderate entropy as particles slide past eachother

entropy of gases

large entropy as particles move freely

Factors that increase entropy

-greater motion
-greater complexity
-weaker ionic force
-large matter dispersal
-particle mass
-temperature
-dissolution

entropy of aqueous solutions

tends to be large as it allows for a greater dispersion of ions

less condensed phase is always...

more favorable

spontaneous process

-occurs naturally under certain conditions
-can be instantaneous or slow

nonspontaneous process

driven by a continual input of energy from an external source

thermodynamics

study of relationships between the energy and work associated with chemical and physical properties

spontaneous processes often result in...

greater dispersal of energy or matter

microstates

special configuration of all the locations and energies of the atoms or molecules in a system

increase of microstates with number of particles

exponential

second law of thermodynamics

all spontaneous changes cause an increase in the entropy of the universe

second law of thermodynamics equation

deltaSuniv = deltaSsys + deltaSsurr

standard entropy change

the total entropy of the products - the total entropy of the reactants

the total entropy of the universe is continuously...

increasing

standard entropy of surroundings =

-deltaH of the system/T

Gibbs free energy

combines S and H to predict spontaneity

Gibbs energy equation

G = H - TS (or changes of)

delta G < 0

free energy decreases; product favored

delta G > 0

free energy increases, reactant favored

gibbs free energy of formation equation

G = sum(nGproducts) - sum(nGreactants)

free energy of a system during a reaction

continuosly decreasing

G = 0

reaction has reached its most stable state (equilibrium)

H-, S+

product favored at all T

H-, S-

product favored at low T

H+, S+

product favored at high T

H+, S-

not product favored

when is the free energy greatest?

when only the reactants are present

delta G = wsys =

-wmax

3 steps of extracting free energy from nutrients

digestion, conversion of enzymes to acetyl coenzyme A, citric acid cycle

digestion

large molecules are broken down into smaller ones