Thermo 1 Flashcards
What are the three states of matter
Solid liquid gas
What are solids characteristics
The attractive forces pull the atoms together in a hard shell then these atoms contact their neighbours
There’s very little space between molecules
The molecules can form ordered arrays (like a highly ordered crystal lattice)
What is the exception to solids having a crystal lattice
What is bad about it
Lead Glass is a solid
But has no lattice crystals structure since doesn’t become ordered when frozen, considered an amorphous solid
Bad because Moved to lead glass water bottles, glistens due to the lead
but lead glass actually allows lead to leach into the drink that it’s holding because ions can diffuse out of the lattice
So some solids can have diffusion through them
What are the characteristics of liquids
The attractive forces pull atoms together with SOME contact between neighbouring atoms
there is NO ordered array
The atoms roll around each other
What is a solvation shell
The solvent forms a shell around the thing in the solvent
Is it true that in liquids there is more volume between atoms
Not fully correct
Exception:
Ice which is a solid has greater volume than water due to more separation between its atoms
Expands when it freezes
What are the characteristic of a gas
Few attractive forces between atoms
the atoms bounce independently
There is no contact between neighbouring atoms, except for when there are collisions
There is pressure due to collisions with the walls
What are the thermodynamic quantities
Temp (T)
Pressure (P)
Volume (V)
Chemical potential (mew)
Entropy (S)
What is temperature
The kinetic energy of something
But an aggregate measurement, not just of one thing but of many together
Needs to be aggregate measurement since:
If you have a proton with a certain kinetic energy
And move with that proton and measure the KE it would be seen as zero
What is pressure
Caused by the impact on the outside (F/A)
Explain how the Vrms equation can differentiate between atoms of diff masses
If you have helium and argon
Helium has lower mass
If same temp and KE, it goes faster based on the equation
Equation in sheet
How can you explain getting burnt using temp
If things stop migrating heat from one to the other we say they’re the same temp
Reason we burn of touch something hot is because the skin tries to be the same temp as whatever it is touching
This shows how temp is comparative
What is volume
The amount of space something occupies
What is chemical potential
Tracks the energy that is accosiated with reactant or thing in a system
What is entropy
Disorder
The energy doesn’t disappear rather increase in the form of entropy
What is the Maxwell Boltzmann distribution Showing
As the hot coffee cools the atoms with the highest energy turn into gas and escape the cup
Meaning the fraction of molecules decreases and the average is going down
What are the condition of an ideal gas
What is the ideal gas law
Molecules don’t interact (non non covalent interactions between them)
The molecules are points (have no volume)
The molecules move freely (have a large mean free path)
PV= nrt
Slode 15
Calc on sheet
What are the appromoxation we use in the ideal gas law
If using the gas condenses to liquid with the ideal gas law:
To get that liquid there has to be attractive forces between the molecules (but we said ideal gasses don’t)
If the liquid has density then the molecules in the liquid must have volume (but we said they are points with no volumes for ideal gas law)
Explain the hard sphere model
Have E vs r (distance between molecules)
As molecules are far away they have no force between them E is zero
As the get closer there is vander waals attractive force which make the E go negative because stable
When too close E goes very high because they start to repel because of vander waals repulsive force
What is virial expansion
Explain the derivation
Have the ideal gas law whcih is a first order approximation
Added a Z term to the gas law which displays compressibility
The squared shows 1 and 2nd order
So PV = RT (1+ BP^1 + CP^2)
Get P in terms of volume
Then PV= RT (1 + B (R T/V) + C (R^2 T^2/V^2) )
Assume the constants R and T are part of B (and C)
Then PV= (1+B/V + C/ V^2 + …)
What do we have to be carful for when doing the viral expansion approximations
Added the R and T constants into B but need to be careful since now B is a function of T
If temp changes, then B changes (same with C)
What are the van der walls constants
b and a
What is the b van der waal constant
It’s a modification where we take into account the repulsive forces and which modifies volume in the ideal gas law
(Vm is molar volume)
P= RT/Vm now P=RT/ Vm - b
The b is the repulsive force constant where we account for the repulsive forces in the hard sphere model plot
getting rid of a chunk of the volume because the volume isnt totally packed together due to the repulsive forces
What is the a vander waal constant
Takes into account attractive forces in the ideal gas law which modifies the pressure
P = RT/Vm turns to P= RT/Vm - a/ Vm^2
Because of the attractive forces, the collision frequency and the collision force are decreased for particles at the edge of the container since they are only being pulled
Explain why the van der waals pressure modification (a) only apply to things at the edge of the container
If we have gas particles in the container
The ones in the center are getting attracted by all the ones around them and get pushed and pulled equally
The particle at the edge only gets pulled inward, hits the side of the container less frequently and less hard because less push and pull
So less collision frequency and less force for that on the side of the container due to the attractive forces
Taking into account the a and b modifications what does the ideal gas law equation turn into
What is this called
P= RT/ Vm-b - (a/ Vm^2)
The van der walls equation
Explain the plot that results from the Vader waals equation:
P= RT/ Vm-b - (a/ Vm^2)
Explain the reality and why the van der waals equation is useful
If you rearrange the equation (on sheet)
You get a Vm^3 term
This means the P vs V graph should look cubic
At very large V, you have very low pressure
At very low V, you have very high pressure
In between you have the cubic squiggle
The vander waals equation was able to predict the result of attraction and repulsion, which is condensation phase change from a gas to a liquid
something that was not ideal and not seen in the ideal gas law equation
In reality,
If we make a P vs V graph for a gas that condenses to a liquid
At high volume (in gas form), the pressure is low
Pressure increases as volume decrease (as the gas condenses)
At some point of the gas condensing there is phase change to a liquid
During this phase change there is no change in pressure
When a liquid, the line is vertical because it is modeled as incompressible
meaning a tiny decrease in volume, the pressure increases greatly because need a lot of pressure to compress the liquid
Over all what did the van der waals equation show
It was wrong but at least able to model that some attraction and repulsion occurs making something non ideal gas like happen as pressure decreases (a phase change)
But the ideal gas law does not show this attraction and repulsion at all, not everything is an ideal gas but it doesn’t account for this
What are the forms of energy
Heat
Kinetic
Gravitational
Electrical
Chemical
Explain the story of energy
Toddler had 10 block and the blocks can’t leave the room
Go in the room only find 9 blocks
Has a bucket of water and you feel the block sliding inside it
Can tell where the block went
Energy is our way of keeping track of something, if it goes missing we can figure out where it went and change it back into something else
