States Of Matter And Changes Of State Flashcards
Gases are well described by ___
Gas laws—no such laws exist for solids or liquids
Kinetic-molecular theory of matter attempts to describe…
All states of matter and conversion between states
Solids have a definite ___ and ___
Volume and shape
Molecules of solids are ___
Closely packed together
What holds molecules together in solids?
Intermolecular forces
Liquids have definite ___ but no definite ___
Definite volume, no definite shape
Liquids have the ability to ___
Flow
Molecules in liquids are ___
Very close together, but can flow past each other
Intermolecular forces of liquids are strong enough to ___; not strong enough to ___
Strong enough to hold molecules in a condensed phase; not strong enough to prevent molecules from sliding past each other
Gases have neither ___ nor ___
No definite shape or definite volume
A gaseous sample will expand to ___
Fill the available space
Intermolecular forces are ___ between gas molecules
Essentially zero
Transitions between states of matter:
- Melting (S-L)
- Freezing (L-S)
- Vaporization (L-G)
- Condensation (G-L)
- Deposition (G-S)
- Sublimation (S-G)
Deposition
Gas to solid
Sublimation
Solid to gas
What are intermolecular forces?
Chemical bonds hold atoms in molecules
Intermolecular forces determine how molecules ___
Interact
Intermolecular forces most directly impact ___
The macroscopic properties of a sample
Repulsion of intermolecular forces
Molecules, atoms, and oppositely charged ions are attracted to each other, but not too close
Intermolecular forces are ___ in nature
Electrostatic
Coulomb’s Law
States that intermolecular forces arise because of the attraction of opposite charges
The driving force in the formation of chemical bonds of all types is the ___
Octet rule
Octet rule
Atoms tend to add, remove, or share electrons so as to wind up with eight valence electrons
Valence electrons
Electrons in the highest energy, or valence shell
Noble gases each have a ___ valence shell
Filled, containing 8 electrons; located in group 8A
Ionic compounds are formed between ___ and ___
Metals and non metals
Metals don’t ___ their electrons very strongly; they are good ___; tend to form ___
Don’t hold onto their electrons very strongly; this is why they are good electrical conductors; tend to form cations
Nonmetals are much better at ___ electrons; tend to form ___
Attracting electrons; tend to form anions
Ionic bond
Results from coulombic attraction between oppositely charged ions
In the solid state, oppositely charged ions settle into a ___, in which every cation is attracted to every anion
Highly organized crystalline lattice
Ionic bonds are generally stronger than ___
Covalent bonds
Ionic compounds are (almost) always ___ under normal conditions
Solids
Example of an ionic compound:
NaCl
Valence bond theory—a covalent bond results from ___
Overlap of two electron clouds, electron sharing
Valence bond theory—electron is bound to the ___ because the negatively charged electron is attracted to the positively charged nucleus by Coulomb’s Law
Nucleus
This allows the electron on atom 1 to spend time around atom 2’s nucleus, and vice versa
VESPR Theory
The intermolecular forces that operate between the molecules in a sample, all of which are caused by how electrons are arranged in the molecule
Non-polar bond
If two atoms of identical electronegativity are bonded together
Polar bond
If two atoms of different electronegativity are bonded together; the electrons spend more time around the more electronegative atom; this creates partial charges
The greater the difference in electronegativity between two atoms, the more ___ the bond
Polar
Intermolecular forces are attractive forces between ___ or ___ or ___
Molecules or atoms or ions
Intermolecular forces are immensely important because these forces hold…
DNA molecules in a helix and are the mechanism for DNA transcription
Three main varieties of IM forces:
- Dipolar
- Hydrogen bonding
- London forces
Dipole-dipole attraction
This is the attraction between the opposite (partial) charges of polar molecules
Dipolar attractions occur only between
Polar molecules
Hydrogen bonding
Hydrogen bonds
London forces are generally the ___ of the three intermolecular forces
Weakest
All common matter experiences ___
London forces
A London force is the result of…
An instantaneous dipole that is created wherever electrons in a molecule are unevenly distributed
___ molecules show more London forces because ___ molecules have more ___
Larger molecules because large molecules have more electrons
London forces are AKA
Van der waals forces
More intermolecular forces mean— ___ boiling and melting points; ___ heats of fusion and vaporization; ___ vapor pressure; ___ viscous liquids
Higher boiling and melting points; higher heats of fusion and vaporization; lower vapor pressure; more viscous liquids
IM forces also affect ___
Solubility—“like dissolves like”
Substances with greater intermolecular attractions have ___ surface tensions
Greater
What is surface tension?
Molecules in the liquid state are attracted to all neighboring molecules by intermolecular forces
A molecule near the surface experiences attractive forces to all of the surrounding surface molecules and with the molecules below it in the liquid
Unbalanced forces create a “skin” on the surface of a liquid
The attractive strength of this skin is called the surface tension
LaPlace’s law—surface tension on a blood vessel wall will depend on the ___ of the vessel
Radius
LaPlace’s Law—the tension on the surface of the blood vessel is directly proportional to the ___ of the vessel
Radius
Aneurysms
Spherical
Represent a dangerous physical means for lowering the surface tension on a blood vessel
Tension for cylinders (LaPlace’s Law)
T = Pr
T = wall tension, P = pressure of fluid within the cylinder, r = radius
Tension for spheres (LaPlace’s Law)
T = Pr/2
Surfactants improve a solvent’s ability to be a solvent by reducing the ___
Surface tension of the solvent
Surfactant =
Surface active agent; commonly known as soaps or detergents
Soaps are derived directly from ___ or ___ through a chemical process called
Fats or oils (triglycerides) through a chemical process called saponification
A triglyceride is a triester derived from ___ and three ___
Glycerin and 3 fatty acids
A fatty acid is a long-chained carboxylic acid having ___ to ___ carbon atoms
12 to 18
Heating a fat or oil with excess sodium hydroxide gives 3 moles of a ___ plus 1 mole of ___
3 moles of a fatty acid salt, plus 1 mole of glycerin
A soap is the ___
Salt of a fatty acid
Detergent
Chemically synthesized, most commonly from soaps
Molecular structure can be tweaked to optimize the physical properties of the detergent
Can be positively or negatively charged, or uncharged
Surfactant molecules stick their polar heads onto ___ while their greasy tails ___
Polar heads onto water; greasy tails stick out of the surface of the water
Bilayer
Basic structure of cell membranes
Tails of surfactant molecules can dissolve in each other to form a double layer
Non polar tails interact with each other, with the polar heads on the outside interacting with the water molecules
Micelles
Tails can dissolve in each other forming a sphere; this creates a non-polar micro environment in the water
Viscosity is a measure of…
A fluid’s resistance to flow
Viscosity increases with ___
Increasing intermolecular forces
Substances having greater intermolecular forces have ___ vapor pressures
Lower
What is vapor pressure?
The most energetic molecules in a liquid have sufficient kinetic energy to break intermolecular forces and escape into the gas phase; once the molecules are free as gases, they exert a pressure, known as the vapor pressure
Vapor pressure and volatility of a liquid increases with ___ temperature
Increasing temperature
At the surface of a liquid, the most energetic molecules can escape from the IM forces into the ___ phase
Gas
Gas molecules near the surface of a liquid can be captured by IM forces into the ___ state
Liquid
When there is a balance between vaporization and condensation, a state of ___ exists
Dynamic equilibrium
Volatility is the tendency of a liquid to ___
Evaporate
Does a more volatile liquid have a higher or lower vapor pressure?
Higher vapor pressure
Does a more volatile liquid have a higher or lower boiling point?
Lower boiling point
Boltzmann distribution
Explains why vapor pressure increases with increasing temperature
Vapor pressures at 200C of common inhalational anesthetics—isoflurane
239 mm Hg
Enflurane
175 mm Hg
Halothane
243 mm Hg
Desflurane
669 mm Hg
Sevoflurane
157 mm Hg
Solid to liquid
Melting
Liquid to solid
Freezing
Liquid to gas
Vaporization
Gas to liquid
Condensation
Solid to gas
Sublimation
Gas to solid
Deposition
Boiling point
The temperature at which the vapor pressure of a liquid equals the ambient pressure
The normal boiling point is the temperature at which the vapor pressure of a liquid equals exactly ___
760 mm Hg
Compounds with more intermolecular forces have ___ boiling points
Higher
Molecules in the liquid state have sufficient intermolecular attractions to keep them from flying away from each other into the ___
Gas state
Compounds with more intermolecular forces have ___ melting temperatures
Higher
Melting point
The temperature at which the solid state reversibly passes into the liquid state
Solid state is characterized by…
Definite shape and volume, which is due to strong intermolecular forces that lock the component molecules into a crystalline array
Liquid state
Component molecules have sufficient intermolecular attractions to keep them from flying away from each other into the gas state, but the intermolecular forces are not strong enough to prevent the molecules from sliding around past each other
Molar enthalpy of vaporization
The heat required to convert 1 mole of a liquid to a gas at its normal boiling point
The molar enthalpy of vaporization is inherently ___, representing an amount of energy that must be added to the sample in order for the phase transition to occur
Endothermic
Molar enthalpy of vaporization represents the energy needed to ___ intermolecular forces and allow molecules to escape into the ___ phase
Break intermolecular forces; allow molecules to escape into the gas phase
Molar enthalpy of fusion
The heat necessary to convert 1 mole of a solid into a liquid at its normal melting point
Fusion is an inherently ___ process
Endothermic
Units for molar enthalpy of fusion
KJ/mole
The heat of fusion represents the amount of energy necessary to overcome the intermolecular forces to the point that the molecules can start to ___
Move around each other
A phase diagram shows combined effects of ___ and ___ on the state of matter
Temperature and pressure
3 key points of phase diagrams:
- Equilibrium lines between states
- Triple point
- Critical point
