thermodynamics Flashcards
thermodynamics
study of heat
heat
energy transfer through temperature
temperature
average kinetic energy of the motions of a molecule
temperature of ideal gas equation
KE= .5mv^2(rms)
v is sqrt of v^2 rms is sqrt(3RT/M)
- t is temp (k)
R is ideal gas constant
M is molar mass
kinetic energy and heat equation
KE= 3/2 t*(r/m)
1. kinetic energy is proportional to temperature
2. details of model apply to ideal gases
what is kinetic energy measured as
temperature in kelvin
system
subset of the universe that is being modeled
internal thermodynamic equillibrium
no macroscopic transfers of energy are taking place
open systems
exchange matter and energy with sorroundings
- human body is an open system
closed system
exchange energy with sorroundings but not matter
- example is a capped test tube
isolated system
canNOT exchange matter or energy with sorroundings
- no true insulators in nature
state functions
variables like energy, temperature, entropy, gibbs free energy and enthalpy
- pressure, volume, density
- describe state of system without describing how it got there
path functions
heat and work
- describe how you got from one equillibrium to another state
zeroth law (thermodynamics)
if system A is in equilibrium with system B and C then systems B and C are in thermal equillibrium with each other
- temp
Fahrenheit scale
32 F is freezing
bp is 212F
body temp is 98.6
celcius scale
body: 37 C
freeze 0 C
conversion from celcius to Farenheit
(F-32)*5/9
conversion from C to F at high temp
9/5
kelvin
0 K= 273 C
K- 273 = C
first law of thermodynamics
for closed systems: the total energy change of a system ΔU equals the transfer of energy into the system via heat minus the work performed by the system on its sorroundings
ΔU= Q- W
- comtribition of heat and work
work being added to a system
+W
work being taken from a system
-W
+Δ U
energy is being added to the system
- ΔU
energy is being removed from the system
+ΔQ
heat is flowing into the system
second law of thermodynamics
if two objects are in contact and not in thermal equilibrium, heat will be transferred from high temperature to low temperature
- the entropy of an isolated system will increase over time
entropy
measure of disorder
connected to energy , how much energy is available to do work
boltzmann’s formula
S = Kb*lnW
- s is entropy
- kb is constant
- w is number of microstates of an observable substance (degrees of freedom)
what does an increase in degrees of freedom mean in terms of entropy
increase df increase entropy
order the amount of entropy from highest to lowest
liquids, solids, gas
solid –> liquid –> gas
entropy and work
Δs = q/T
can entropy be decreased
yes, but it takes considerable energy (if you break a glass bottle and it shatters it is not easy to piece together)
major entropy concepts for MCAT
- energy will flow from hot to cold items
- entropy inevitably increases in a true isolated system
third law of thermodynamics
at absolute o (0 Kelvin) a crystal structure has an entropy of 0
t/f: heat and temperature are different things
TRUE
heat is a transfer of energy, temperature is average kinetic energy
units of heat
j, calories
heat transfer methods
- conduction
- convection
- radiation
conduction
two objects with different temperatures touch and heat transfers from hot to cold
convection
heat transfer between two objects due to the circulation of fluid
- thermal differences due to the densities of fluids
radiation
no direct contact
- heat transfer via electromagnetic waves
thermal expansion
idea that as temperature increases, the object expands
exception to thermal expansion
ice is less dense than water and reaches peak density at 4C
solid expansion equation
ΔL= alphaL *ΔT
- measure change in L
- alpha is coefficient of thermal expansion that is specific to substance
liquid expansion equation
ΔV = alphav*ΔT
ideal gas equation
PV=nRT
isothermic system
temp constant on a pressure volume graph
adiabatic system
no heat or matter is transferred between a system and its sorroundings
- constant entropy
- steeper slope than isothermic
isobaric
constant presssure
