Chapter 12: Changes Of Phase Flashcards
Describe a closed system
One that matter can’t enter or escape but NRG can; but theoretically no system can be completely closed
Define equilibrium
The dynamic condition in which 2 opposing changes occur at equal rates in the same closed system
Why is the closed system a theoretical construct?
Bc no system can be completely closed
Defoe a phase and give and example
Any part of a system with uniform composition and properties
Ex: flask of eyed with a stopper in it is a liquid/vapor closed system. Liquid and vapor being the phases
What can wayer molecules at the surface do ?
Gain NRG and escape the surface(evaporate)
Why can water molecules at the surface evaporate easier?
These molecules at the surface are not held in place by surrounding molecules
When will an equilibrium be established?
If temperature remains constant there is a point where the amount of evaporation will equal the amount of condensation
At equilibrium what happens tithe relative amounts of liquid and vapor?
Remain constant but not necessarily equal
What is the equilibrium expression
Liquid + heat vapor
What happens when a system at equilibrium experiences stress? Le Chaltiers theory of stress.
A new equilibrium will be established that will minimize stress
State the equation for the effects of temperature
Liquid + NRG vapor
What is the result when NRG is adde to a system at equilibrium and vice versa
The rxn is pushed forward
The rxn is pushed into reverse
Both forming new equilibrium a
State the equation for the effects of p
Liq + NRG vapor
Which state of matter responds from a change in p
Gases
Explain how an increase in P will effect the system and decrease
Pushes equilibrium to the left and decreasing to the right
What other stress has the same effect as V
P
What happens when a volume of gas decreases and vice versa
P increases
Decreases ( think Boyles law)
Define EVP
The P exerted by a vapor that is at equil. With it’s liquid
When will wayer molecules gain enough KE to move to the surface
When T increases
What causes P of vapor to increase?
Increase in temperature
Define volatile liquid and give an example
Evap. quickly Bc weak attraction between molecules
Ammonia gas
Define nonvolatile liquids
Don’t evaporate fast Bc strong attraction between molecules
Water oil
Define booling point
The change of a liq to a vapor within the liquid as well as the surface
When does booling occur
when EVP = ATM P at a certain place and time
How does boiling point vary with P
Directly
How does altitude affect booling point
At high P booling point is slightly lower and vice versa
What happens to the temp at booling point
Constant
At what T is boiling point at SP
100C
How can you boil water faster
Above SP
Define molar heat of vaporization
Amount if NRG needed to vaporize 1 mil of a liquid at it’s boiling point
When is there a strong attractive force between molecules
When the molar heat of vaporization is high
Compare freezing and melting points for specific substances
Occur at the same temperature
Wrote te equation of freezing and melting
Solid + NRG liq
How will a solid become a liq and vice versa
Gaining or losing NRG
Define te molar heat f fusion
Amount of heat to melt 1 mil of a solid @ it’s melting point
What does the molar heat of fusion depend on
The attractive forces between molecules in the substance
Define sublimation and deposition and give examples of each
@ very low Temp liquids can’t exist and so a vapor will exist at equilibrium with its solid
Sub. Dry ice snow moth balls
Dep. snow
What is the phase change diagram
a P vs V graph showing the conditions at which the phases of a diff. Substance exist
Define triple point
T and P at which all 3 phases co- exist
Define critical T
Above this temp substance cannot exist as a liq. Regaurdless of P
Define critical P
Lowest P at which a substance can exist as a liq. While at its critic T
Describe a water molecule and it’s bond angle
Polar covalent bonded molecules formed by 105 Degree bond angles
Define hydrogen bond a
Weak bonds between H and a very electronegative element (N F O) bond is fluid and changeable
Described H bonds in liquid form
Fluid an transient
Describe the H bonds in ice
Rigid unchangimg framework that traps pockets of air
When does te maximum density of water occur
4C
Name four properties of water
Transparent
Odorless
Tasteless
Colorless
