Lecture 3

what is a system and surroundings in thermodynamic problems
a system is the macroscopic body under study, and the surroundings are everything else
what are the three systems of thermodynamic classification
open, closed and isolated
what do open systems do
open systems exchange both mass and energy with it’s surroundings
what do closed systems exchange
closed systems exchange energy but not mass with their surroundings
what do isolated systems exchange
isolated systems do not exchange either mass or energy with its surroundings
what are state functions
such properties that describe the state of a system
there are only two ways to transfer energy between systems, what are they
heat and work
what is heat
the natural transfer of energy from a warmer body to a cooler body
what is work
any transfer of energy that is not heat
what are the three forms of heat
conduction, convection and radiation
what is conduction
thermal energy transfer via molecular collisions
give an example of conduction
when higher energy molecules transfer some of its energy to lower energy molecules via molecular collision
what is convection
differences in pressure and density drive warm fluid to cooler fluid
what is radiation
thermal energy transfer via electromagnetic waves- when a metal is heated it glows bright orange and then blue- this is electromagnetic waves
what is Newton’s law of cooling
the cooling of a body is directly proportional to the temperature difference betweenthe body and its environment
in constant pressure conditions, how can you calculate the work being done
w= P delta V
how can you find the average kinetic energy of a single molecule in any fluid
3/2 kT
what is change in enthalpy
delta H= delta U + PdeltaV
An element in its standard state at 25 C is arbitrarily assigned
an enthalpy of 0 J/mol
for reactions involving no change in pressure, the enthalpy equals
the enthalpy equals the heat
when there is an absence of work within a reaction
the enthalpy is equal to the change in energy
what is the heat of the reaction
this is the change in heat from the reactants to products
what does endothermic mean
the enthalpy change is positive
what does exothermic mean
the enthalpy change is negative
what sort of chemical state does the activation energy hill represent
it represents the transitional state
a catalyst affects the what but not the what
it affects the rate but not the equilibrium
what is the term entropy
this is the tendancy toward disorder
something with higher entropy has higher
probability
what does the second law of thermodynamics state
that entropy of an isolated sysytem will never decrease
only reactions equal to zero are considered ideal reactions and only ideal reactions have
zero change in enthalpy
what dictates the direction of a reaction
entropy
reactions at equilibrium have achieved
the maximum universal entropy
when temperature, volume and pressure increase, so does
entropy
when is zero entropy applied
with any pure substance or any molecule at absolute zero
a negative delta G indicates
spontaniety
x

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