(Ch) Chapter 8: Phases And Phase Changes

Front 1

Name the two types of molecular arrangement of solids

Back 1

Crystalline and Amorphous

Front 2

Crystalline Solids

Back 2

Crystalline solids have a specific three dimensional molecular structure with a lattice of repeating structures

Front 3

Amorphous Solids

Back 3

Amorphous solids have molecules that are fixed in place but do not have the three dimensional structure that crystalline solids have (ex: plastic, glass, wax)

Front 4

Ionic Solids

Back 4

Aggregates of positively and negatively charged ions that repeat according to a definite pattern of alternating cations and anions.

Front 5

Physical Properties of ionic solids

Back 5

They are poor conductors in the solid state but good conductors when dissolved in a liquid. They have high melting points and boiling points

Front 6

Metallic Solids

Back 6

Metallic solids are solids that are composed of metal atoms packed together in a very close manner. They are arranged in a staggered manner in which each molecule fits into the indentation of two other molecule below it.

Front 7

Unit Cells

Back 7

Repeating Units of crystals

Front 8

Simple Cubic

Back 8

As the name suggests, the simple cubic is a simple three dimensional cube with atoms at each corner of the cube.

Front 9

Body Centered Cubic

Back 9

Same design as the simple cubic with the exception that there is an atom at the center as well

Front 10

Face Centered Cubic

Back 10

Same design as the simple cubic with the addition of half an atom at each face of the molecule (half because one half is in the molecule while the other half is out of the molecule.

Front 11

Define miscible.

Back 11

Two solutions that can mix; ethanol (CH3CH2OH) and water.
The miscibility of two solutions depends on the the polarity of the solutions. If the solutions are polar they will mix and if they are not they will not mix

Front 12

Immiscible

Back 12

Two solutions that can't mix; oil and water

Front 13

Emulsion

Back 13

Homogenous mixture of discrete particles formed with two immiscible solutions

Front 14

Vaporization (or evaporation)

Back 14

Liquid to gaseous state

Endothermic process (energy is supplied)

Front 15

Deposition

Back 15

Gas to solid state; reverse of sublimation

Front 16

Melting (or fusion)

Back 16

Solid to liquid state

Front 17

Condensation

Back 17

Gaseous to liquid state

Front 18

Boiling Point

Back 18

The temperature at which the vapor pressure of the liquid is equal to the ambient pressure.

Front 19

Vapor pressure

Back 19

The pressure that gas exerts over a liquid

Front 20

Where does vaporization occur in a liquid?

Back 20

Vaporization occurs throughout the liquid not just at the surface of the liquid

Front 21

The transition from solid to liquid

Back 21

Fusion or Melting

Front 22

Melting point of amorphous solids and crystalline solids

Back 22

Amorphous solids tend to have a melting point that ranges whereas crystalline solids have a very specific and fixed melting point.

Front 23

Sublimation

Back 23

The transition of a solid to a gas

Front 24

Deposition

Back 24

The transition from a gas to solid

Front 25

What happens to temperature during a phase change?

Back 25

As a phase change occurs, the temperature of the compound remains constant. The reason for this is that the energy that is being added as heat is directed toward the change of phase.

Front 26

What do the lines on a phase diagram tell you?

Back 26

The lines divide up the three different phases. The line that divided two different phases charts out the temperature and pressure points at which the two phases are in equilibrium.

Front 27

Triple Point

Back 27

The point on a phase diagram in which all three states exists simultaneously

Front 28

Critical Point

Back 28

The temperature and pressure at which there is no distinction between the phases.

Front 29

Colligative Properties

Back 29

Properties that depend on the AMOUNT of a solute that is dissolved in a solution and not necessarily the identity of the solution itself.

Front 30

Examples of colligative properties

Back 30

Freezing point depression, boiling point elevation, osmotic pressure

Front 31

Raoult's Law

Back 31

This law states that for a given solvent, the vapor pressure of the solvent is the product of the mole fraction of the solute and the vapor pressure of the pure the pure solvent

Front 32

If you were to add a solute to a pure solvent, what would happen to the vapor pressure of the solvent?

Back 32

The vapor pressure of the solvent would go down.

Front 33

Ideal Solutions

Back 33

Solutions that obey Raolt's Law

Front 34

Boiling Point Elevation

Back 34

Adding a solute will lower the vapor pressure of a given solution. If the vapor pressure is lowered then more energy will be needed to make the vapor pressure of the solvent equal to the ambient vapor pressure (which is boiling point).

Front 35

Freezing point depression

Back 35

Freezing is the formation of a lattice structure of the solvent. If solute is added to a solvent, the solute will interfere the formation of the lattice. The easier a solution can form a lattice the less cold it needs to be which means that the freezing point is higher. However, if there is something interfering with the freezing process, like in the case of a solute, then the solvent will only freeze at a lower temperature.

Front 36

Osmotic Pressure

Back 36

A tube is divided into two compartments. One side is filled with water and the other is filled with salt water. The separation between the two compartments is controlled by a membrane that only allows water through. The osmotic pressure is the pressure that is exerted by the pure water side on the other side due to the fact that water will rush into the other side of the tube to establish an equilibrium

Front 37

Regions of a phase change diagram.

Back 37

(left to right) Solid - Liquid - Gas

Solid: high P, low T
Liquid: high P, high T
Gas: low P, high T

Front 38

Crystallization (freezing)

Back 38

Liquid to solid state

Front 39

Define
1) Condensation,
2) Crystallization,
3) Fusion,
4) Vaporization,
5) Sublimation,
6) Deposition

Back 39

All transitions.
Condensation: gas-liquid
Crystallization (or freezing): liquid-solid
Fusion (or melting): solid-to-liquid
Vaporization: liquid-gas
Sublimation: solid-to-gas
Deposition: gas-to-solid

Front 40

Define temperature, and describe its relation to kinetic energy and entropy of molecules

Back 40

Temperature is a measure of the amount of internal kinetic energy (energy of motion) that molecules haves.

The average KE of molecules of a substance directly affects its state or gas; whether gas, solid, or liquid.
Average KE of the molecules is related to entropy (degree of disorder); higher the average KE of the molecules, the greater its entropy.

Solids: ordered, least energetic
Gases: least ordered, most energetic

Front 41

Exothermic phase transitions

Back 41

EXOTHERMIC PROCESSES (Release heat energy, heat energy is released, decreasing internal KE and entropy)

CONDENSATION, CRYSTALLIZATION/FREEZING, DEPOSITION

Going from least to most ordered (least to most stable); molecules are brought together

Heat is released, internal KE and entropy decreases

GAS-to-LIQUID-to-SOLID

HEAT IS RELEASED from system
INTERNAL KE AND ENTROPY DECREASES

Front 42

Endothermic Phase Transitions

Back 42

Require energy input (spreading molecules apart)

Melting/fusion, vaporization, sublimation ABSORB HEAT

SOLID-to-LIQUID-to-GAS (most ordered, least energetic phase to transition to most energetic, least ordered phase): requires input of energy

Energy input causes internal KE, and thus entropy, to increase

Front 43

Negative Deviations from Raoult's Law

Back 43

Vapor pressure is LOWER than expected from Raoult's Law

Indicates adhesive forces between different components are stronger than cohesive forces between like components

Each component remains in condensed phase by attractive forces stronger than the pure liquid.

Observed w/ polar-polar solutions

Front 44

Positive Deviations from Raoult's Law

Back 44

Indicates cohesive forces between like molecules are greater than the adhesive forces; molecules are repelled by one another (nonpolar + polar)

Dissimilarities of polarity or internal pressure will lead both components to escape solution more easily.

Vapor pressure will be greater than expected from the Raoult's law, showing positive deviation.

Front 45

Straight lines versus curved lines on Mole Fraction versus Pressure (P) graph

Back 45

Straight lines result from Rauolt's Law preductions

Curved lined produced by nonideal conditions

Positive heat of solution forms weaker bonds = molecules repeal, positive deviation; nonpolar + polar mixtures


Negative deviation, stronger bonds form, negative heat of solution, fewer molecules are able to break free from the surface; vapor pressure is decreased from Rauolt's Law prediction