States of Matter Flashcards
Physical Properties of Gases
- Highly Compressible
- Infinately Miscible
- Theramlly Expendable
- Low Density
Gases exert pressure on its environment because the molecules are in constant motion
Boyle’s Law
At constant temperature, pressure is inversly proportional to volume
P1V1 = P2V2
Charle’s Law
At constant presssure, volume is direcly proportional to temperature
V1/T1 = V2/T2
Avagadro’s Law
At constant pressure and temperature, volume is directly proportional to the nember of moles
V1/n1 = V2/n2
Ideal Gas Law
PV = nRT
Note: only applies for ideal gases
* Calculations for real gases must be accomidated for particle volume and interparticle attraction
Dalton’s Law of Partial Pressure
In a mixture of non-reacting gases, the total pressure is the sum of the partial pressure of the individual gases
P(a) +P(b) = P(total)
or
P(total) = n(total) x (RT/V)
or mole fraction
Mole Fraction
Gases
An alternative way to express Dalton’s law of partial pressure.
X(a) = P(a)/(P(total))
Kinetic Molar Theory of Gases (Name the 5 rules)
A model of an ideal gas developed to explain the behaviour of real gases
Gases are made up of particles with no defined volume
* The particle size is so small compared to the distance seperating them that their volume is considered to be neglible
Particles are in continuous, random motion
* They have kinetic energy
Particles move independantly and experience no interparticle forces
* No attraction/repulsion
* They don’t have potential energy
Particles colide with eachother and with the walls of the container
* Colisions are elastic (no net loss of energy)
The average kinetic energy is the same for all gases at a given temperature
* Kenetic energy is proportional to temperature
What is the calculation of pressure in one dimension? What about 3?
1D. P = F/A
3D. P = (2/3)x((n(N(a)(1/2)mu^2)/V)
u^2 = Mean of the square to the speeds
m = Mass of the particles
N(a) = Avagadro’s number
What’s the requirement to be an ideal gas? What happens if the gas is above or below that value?
(PV)/(nRT) = 1
If above, the effect of particle volume dominates
If below, the effect of interparticle attractions predominates
What are the two things that can happen in gasses that make them fail to comply with ideal gas law?
They can experience weak interparticle attraction
They can occupy a finite volume
Van der Waals Equation
The equation that takes into accunt the interparticel attraction and the volume occupied by gas particles
P = (nRT)/(V-nb) - a(n/V)^2
b = Correction to volume
a = Correction to interparticle attraction
When is ideal gas behaviour oberved?
At low pressures and at high temperatures
Sublimation
The transfer from a solid to a gas
Deposition
The transfer from a gas to a solid
True or False
The transfer from a solid to a liquid is an exothermic reaction
False
It’s Endothermic
(Melting ice in water makes the water colder)
What are the commercial uses of supercritical (SC) fluids?
- Caffine is extracted with it
- Fat is reduced with it
- Used in dry cleaning
What do you get under the combination fo the critical temperature (T(c)) and the critical pressure (P(c))?
A supercritical fluid
* This is very useful
Properties of Solids
- Molecules do not have the freedom of movement
- A solid keeps its shape no matter what the shapre of its container is
- The particles of a solid are very close together and interparticle forces ar every strong
- Density is a very improtant property
Properties of Liquids
- Lack of rigidity and of compressibility
- Take the shape of the container they occupy
- Viscosity of a liquid can be measured
- Density is higher than that of a gas
Types of intermolecular forces
- Ion-Dipole (P)
- Dipole-Dipole (P)
- H-bond (P)
- Induced Dipole (T)
- Dipole-induced dipole (T)
- London dispersion (T)
P = Permanant
T = Temporary
Hydrogen bonding
A hydrogen bond results when a H that is covalently bonded to a more electronegative atom (N, O, F) interacts withat an electornegative atome of aanother molecule
* ONLY APPLIES TO N, O, AND F
* This is another type of dipole-dipole bond, just stronger
What are the types of temporary dipoles
Thes occur in atoms that have the same, or very similar electronegativities
- Ion-induced dipole
- Dipole-induced dipole
- Induced dipole-induced dipole (london dispersion)
What are the characteristics of London Dispersion
- Creates an instantaneous intermolecular (or interparticle) attraction that is short-lived and weak
- The higher the atomic mass (molar mass), the higher the probability for the formation of instant dipoles of larger magnitude
- They are not strong enough to lead the formation of liquid in low molecular weight compounds at room temperature
What factors impoact the strength of London Dispersion in a molecule
- Molar mass
- Shape
- More surface area = stronger LDF
What are the factors to consider when deciding about the intensity of intermolecular forces
Comparing non-polar compounds
* Molar mass
* Molecular Shape
Comparing polar and non-polar compounds with comparible molar masses
* Polar substances have higher IMF
When comparing polar compounds
* Presence of H-bonding
Surface tension
The resistance of a liquid to go flat on a surface (increase surface area)
* High surface area = Strong IMF
* The stronger the IMF, the higher the surface tension
Capillarity vs Wetting
Capillarity - The spontaneous rising or decsent of a liquid in a capillary tube
Wetting - The ability of a liquid to maintain contact with a surface
Both involve the competition of cohesive and adhesive forces
Cohesive vs Adhesivse Forces
Cohesive Forces
* The IMF betwen the molecules of a liquid
Adhesivse Forces
* The forces of attraction between molecules of a liquid and the particles presant on the surface of the container
If adhisive is stronger than cohisive, the liquid rises and forms concave meniscius
If cohisive is stronger than adhesive, the liquid descends and forms a convex meniscius
Viscosity
The resistance of a liquid to flow
* High viscosity = high IMF
* Raising temperature lowers viscosity
Note: in engine oils this is a very important trait
Eg. 5W-3o vs 10W-3o
Higher W = higher viscosity
o refers to risistance to thinning
Vapor Pressure of liquids
The Equilibrium of the vapor above the liquid. It results from the evaporation of the liquid.
* The stronger the IMF in the liquid, the higher the boiling point, the lower the vapor pressure
What are the two general catagories of solids
Crystaline Solids
* Characterizeed by a highly ordered assemply of their components
Amorphous Solids
* Characterized by a random assemply of their components
What are the types of crystaline solids
Discrete molecular solids
* Non-polar
* Soft
* Low melting point
* Does not conduct
* Polar Hydrogen bonded
* Soft
* Low to moderate melting points
* Poor Conductors
Extended Structures
* Ionic
* Hard & brittle
* High melting point
* Non-conductors in solid, good conductors in liquid
* Giant Covalent
* Very Hard
* High melting point
* Poor conductor
* Metalic
* Soft to hardish
* Usually high melting point
* Ductile
What are the types if cubic lattices?
What are their coordination numbers?
Simple Cubic (or primative)
* CN = 6
Body-Centered Cubic (BCC)
* CN = 8
Face-Centered Cubic (FCC)
* CN = 12
CN = Coordination number = The number of neighbors that a central particle is in contact with in a crystaline structure
Square-packing vs close-packing
Crystals
Square packed structure
* Each atom has 4 closest neigbors
Close-packed strucure
* Each atom has 6 closest neighbors
What are the types of close packing?
Packing leading to hexagonal close packing
* Atoms of the 3rd layer sit on the tetrahedral holes which means directly on top of atoms in layer A
Packaging leading to cubic close packing
* ABC ABC type arrangement
* Atoms of the 2nd layer (layer B) are surrounged by 6 atoms in the same layer, 3 atoms in layer A and 3 atoms in layer C
Formation of alloys
Atoms of a metal occupy the intersitces (holes) of another metal
* Increases mechanical strength
* 2nd metal contributes additional valence electrons to metallic bonding
Density of metallic solids
Information required to calculate density of metallic solids
* Number of atoms in a unit cell (Net attoms)
* Length of the unit cell
* Volume of the unit cell
Density = mass/volume
Are alcohols soluble in water?
4C and 5C alcohols have borderline solubility in water,
Alcohols of 6C and more are soluble
What’s the magic ratio for molecular weight to take precedence over polarity in determining boiling point
The non polar molecule must move a M (g/mol) 3 times larger than the polar molecule
True or false
Metals and metal alloy solids always have extended structure
True
The atoms are held together by the “sea” of delocalized electrons
Diamond vs Graphite structure
Each carbon in diamond is bonded to 4 other carbons
* No free electrons sp3
In graphite, carbon atoms are layered, each charbon is bonded to 3 other carbons
* Sheets stack on top of eachother and are held together by Van der Waals forces
Graphite vs Bucky Ball vs Carbon Nanotubes Structure
Graphite
* Carbon bonded to three other carbons in a 2D sheet
* Many layers
* Extended structure
Bucky Ball
* Molecular sturcture
* Same bonding as in graphite
Carbon Nanotubes
* Same structure as a single sheet of graphite, just in a roll
What force dominates when (PV)/(RT) < 1
Interparticle attraction
At low pressures, heavy molecules fall here
“a” is correction to pressure
What force dominates when (PV)/(RT) > 1
Particle volume
This is the lighter gases
* At higher pressures, heavy gases also fall here
“b” is correction to volume
How do you find density of air
D = MP/RT
