Chapter 12-3 Changes Of Phase Flashcards
Define closed system
One that matter cannot get in or out but nrg can
Define equilibrium
Dynamic condition which 2 opposing changes occur at equal rates in the same closed system
Define theoretical construct
No system can be completely closed, but we can come close
Define phase
Any part of a system with uniform composition and properties
Example of phase
A flask of water with a stopper in it is a liquid/vapor closed system. Phases are liquid and gas
Where do h2o molecules evaporate at when they gain nrg?
The surface
What are h2o molecules below the surface held in place by?
By surrounding molecules
Why do surface molecules evaporate more easily?
They are not held at the surface
What will happen to some of the molecules that escape?
Condense
When will equilibrium be established?
When the amount evaporating equals the amount condensing
Describe the relative amounts of liquid and vapor at equilibrium
The amounts are constant but not equal
Write an equilibrium expression
Liquid + heat Vapor
Describe Le Chatlier’s principle
When a system at equilibrium is distributed by a stress a new equilibrium point will be established that will minimize the stress
What is stress?
Change in P, V, or T
What happens to a rxn when nrg is added?
There will be more vapor at equilibrium point and less liquid
What happens to a rxn when nrg is removed?
More liquid at new equilibrium point and less vapor
What phase responds to P changes?
Gases
What will an increase in P do to the rxn equilibrium?
Push the rxn to the left
What will a decrease in P do to the rxn equilibrium?
Push the rxn to the right
What happens to the P of a system when V is decreased?
The P increases
What happens to the P of a system when V is increased?
The P decreases
Define Equilibrium vapor pressure (EVP)
The P exerted by a vapor that is at equilibrium with its liquid
What is EVP dependent on?
T
What happens when the T of a liquid is increased?
More liquid molecules will escape the surface because of increased energy
