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Bchem 471 > Thermo 1 > Flashcards

Thermo 1 Flashcards

1
Q

What are the three states of matter

A

Solid liquid gas

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2
Q

What are solids characteristics

A

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)

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3
Q

What is the exception to solids having a crystal lattice

What is bad about it

A

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

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4
Q

What are the characteristics of liquids

A

The attractive forces pull atoms together with SOME contact between neighbouring atoms

there is NO ordered array

The atoms roll around each other

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5
Q

What is a solvation shell

A

The solvent forms a shell around the thing in the solvent

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6
Q

Is it true that in liquids there is more volume between atoms

A

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

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7
Q

What are the characteristic of a gas

A

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

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8
Q

What are the thermodynamic quantities

A

Temp (T)

Pressure (P)

Volume (V)

Chemical potential (mew)

Entropy (S)

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9
Q

What is temperature

A

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

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10
Q

What is pressure

A

Caused by the impact on the outside (F/A)

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11
Q

Explain how the Vrms equation can differentiate between atoms of diff masses

A

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

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12
Q

How can you explain getting burnt using temp

A

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

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13
Q

What is volume

A

The amount of space something occupies

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14
Q

What is chemical potential

A

Tracks the energy that is accosiated with reactant or thing in a system

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15
Q

What is entropy

A

Disorder

The energy doesn’t disappear rather increase in the form of entropy

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16
Q

What is the Maxwell Boltzmann distribution Showing

A

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

17
Q

What are the condition of an ideal gas

What is the ideal gas law

A

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

18
Q

Slode 15

A

Calc on sheet

19
Q

What are the appromoxation we use in the ideal gas law

A

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)

20
Q

Explain the hard sphere model

A

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

21
Q

What is virial expansion

Explain the derivation

A

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 + …)

22
Q

What do we have to be carful for when doing the viral expansion approximations

A

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)

23
Q

What are the van der walls constants

A

b and a

24
Q

What is the b van der waal constant

A

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

25
Q

What is the a vander waal constant

A

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

26
Q

Explain why the van der waals pressure modification (a) only apply to things at the edge of the container

A

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

27
Q

Taking into account the a and b modifications what does the ideal gas law equation turn into

What is this called

A

P= RT/ Vm-b - (a/ Vm^2)

The van der walls equation

28
Q

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

A

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

29
Q

Over all what did the van der waals equation show

A

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

30
Q

What are the forms of energy

A

Heat

Kinetic

Gravitational

Electrical

Chemical

31
Q

Explain the story of energy

A

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

Bchem 471 (24 decks)

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