Chem. - Ch.13 Phase Changes Review
Enthalpy of Fusion
The energy required to melt 1 gram of a substance at its melting point
Enthalpy of Vaporization
The energy required to vaporize 1 gram of a substance at its boiling point
Melting Point
The freezing point of a liquid is the same as the _____ of a solid for a particular substance
Vapor Pressure
The higher the temperature, the higher the _____ of a gas
Atmospheric Pressure
The lower the _____, the lower the boiling point
Critical Pressure
The only pressure which will cause a gas to liquefy at critical temperature
Phase Diagram
A graph of pressure versus temperature that shows in which phase a substance exists under different conditions of temperature and pressure
Boiling
A process which occurs when the vapor pressure of a liquid is equal to the atmospheric pressure
⇌
A reaction at equilibrium is represented by _____
Melts
A solid _____ when the patterned arrangement of the solid breaks down
Decrease
An increase in vapor pressure causes a _____ in volume
1. Heat energy disrupts hydrogen bonds 2. The amount of energy required depends on the strength of the bonds 3. The melting point is the temperature at which the forces holding its crystal lattice together are broken and it becomes a liquid 4. The melting point of amorphous substances may be unspecified
Describe the Process of Melting:
1. Many solids can become gases without first becoming a liquid 2. Some solids sublime at room temperature 3. The process of freeze drying is an example of sublimation
Describe the Process of Sublimation:
1. In liquid water, some particles have more energy 2. Particles that escape from liquid enter the gas phase 3. When vaporization occurs only at a surface it is called evaporation 4. The pressure exerted by a vapor over liquid is called vapor pressure 5. The temperature at which vapor pressure equals atmospheric pressure is called the boiling point
Describe the Process of Vaporization:
Throughout The Liquid
The difference between evaporation and boiling point is that evaporation occurs only on the surface of a liquid, while boiling occurs _____
Critical Point
For water, it is the point that indicates the critical pressure and critical temperature above which water cannot exist as a liquid (Water vapor will not change into a liquid)
Molasses, Glycerol
Give some examples of Nonvolatile Substances:
Rubbing Alcohol, Ether
Give some examples of Volatile Substances:
Le Chatelier's Principle
If stress is applied to a system of equilibrium, the system will tend to readjust so that the stress is reduced
Dynamic Equilibrium
In _____, molecules escape & return to the solid or liquid surface continuously, and at the same rate
Evaporation
Is when vaporization occurs only at the surface of a liquid
Liquid/Vapor Equilibrium
Liquid & Vapor phases coexist and Vaporization & Condensation occur on this line
Critical Temperature
Low _____ means there are weak forces between molecules
1. Deposition & Sublimation 2. Melting & Freezing 3. Vaporization & Condensation
Name 3 Opposing Processes:
Melting, Vaporization, Sublimation; Freezing, Condensation, Deposition
Name 3 Phase Transitions that are Gaining Energy; Name 3 that are Losing Energy
Dry Ice (Solid Carbon Dioxide), Moth Balls (Naphthalene), Solid Iodine
Name substances that Sublime:
Melting Point
Of a crystalline solid, this is the temperature at which the forces holding its crystal lattice together are broken and it becomes a liquid
Condensation
Phase Transition that involves "Gas to Liquid"
Deposition
Phase Transition that involves "Gas to Solid"
Vaporization
Phase Transition that involves "Liquid to Gas"
Freezing
Phase Transition that involves "Liquid to Solid"
Sublimation
Phase Transition that involves "Solid to Gas"
Melting
Phase Transition that involves "Solid to Liquid"
Condensation
Process by which a gas or vapor becomes of liquid
Vaporization
Process by which a liquid changes to a gas or vapor (Opposite of Condensation)
Sublimation
Process by which a solid changes directly to a gas without first becoming a liquid
Deposition
Process by which a substance changes from a gas or vapor to a solid without first becoming a liquid
Opposing Processes
Processes with a relationship where one is gaining energy and the other is losing energy
Solid/Liquid Equilibrium
Solid & Liquid phases coexist and Melting & Freezing occur on this line
Solid/Vapor Equilibrium
Solid & Vapor phases coexist and Sublimation & Deposition occur on this line
Volatile Substance
Substances that boil at a low temperature and evaporate quickly at room temperature
Nonvolatile Substances
Substances that evaporate slowly at room temperature and have a high boiling point
Lower Melting Points
Substances with Weak Intermolecular Forces have _____ than substances with Strong Intermolecular Forces
Strong Intermolecular Forces; Weak Intermolecular Forces
Substances with low vapor pressure have _____; And those with high vapor pressure have _____
Vapor
The _____ form of a substance is the gaseous form of a solid or a liquid at room temperature (25°C)
Triple Point
The point on a phase diagram that represents the temperature and pressure at which 3 phases of a substance can coexist
Liquefaction
The process of changing a gas to a liquid
Critical Temperature
The temperature above which no pressure will liquefy a gas
Freezing Point
The temperature at which a liquid is converted into a crystalline solid
Melting Point
The temperature when the vapor pressure for a solid equals the vapor pressure of a liquid
1. Cooling the temperature 2. Increasing the pressure
What are 2 ways to Liquefy a Gas?
101.325 kPa, 760 mmHg, 760 torr, 14.7 lb/in²(psi), 1.01325 Bar
[This is most likely given on Graphs] Name the Measurements for Standard Atmospheric Pressure (1 atm):
Ionic Compounds
_____ do not exert a significant vapor pressure because the inter-ionic forces are too strong to be overcome