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Question 1

Boltzmann distribution

Answer 1

A formula describing the statistical distribution of particles in a system among different energy levels.

Question 2

Applications of the Boltzmann-distribution I.: Nernst equation

Answer 2

• P.E = Charge * Voltage
• Has long formula

Question 3

Applications of the Boltzmann-distribution II.: equilibrium and rate of chemical reactions. (The Arrhenius plot)

Answer 3

• In chemical reactions atoms must transition from one energy state A, to state B.
• In equilibrium the distribution between the states can be calculated with formula.
• na/nb = K (equi. Constant)
• Arrhenius plot, Graph K / 1/t and the slope gibes the energy distribution between 2 states.

Question 4

Applications of the Boltzmann-distribution III.: barometric formula

Answer 4

• In thermal equilibrium we can measure decreases in atmospheric density vs altitude by this formula.

Question 5

Applications of the Boltzmann-distribution IV. electric conductivity of semiconductors.

Answer 5

• Depends on number of electrons which are able to transition from valence band through gap to the conduction band.
• Number increases with T.
• Using Boltzmann distribution we can calculate fraction of electrons that are able to cross the gap.
  (Delta e)

Question 6

Macrostate and microstate in thermodynamics

Answer 6

• Microstate: Examination of molecular state of system and instant state. (Location of particles, velocity of particles, momentum)
• Macrostate: Examine whole system (Pressure, Temperature)
• In Thermal equilibrium the macro states stay constant whole microstate always changes.

Question 7

Boltzmann’s definition of entropy

Answer 7

S = k * ln
S = entropy (extensive quantity of heat)
- Number of micro states which belong to a macrostate

Question 8

Kinetic gas theory

Answer 8

• Particles are small compared to volume
• Constant random motion
• Collision of particles is elastic
• Particles exert pressure when colliding with container wall
• Molecular speed is proportional to temperature

Question 9

Maxwell-Boltzmann velocity distribution

Answer 9

• Upon increasing temperature, average absolute value of molecular speed increases
• Width of distribution increases due to increase in interactions between molecules

Question 10

The Ideal gas

Answer 10

• Non realistic gas
• Composed of molecules which follow the kinetic gas theory
• Pv = nrt

Question 11

The real gas

Answer 11

• Contrary to ideal gas
• Particles are not point like
• Volume is not negligible
• Less volume available for motion
• Interaction between particles arise and pressure becomes reduced
• Explains possibility of condensartion

Question 12

State equation of real gases

Answer 12

() () = nkt

Question 13

Pressure of ideal gases

Answer 13

Pv=nRt

Question 14

The crystalline state (unit cell, crystal defects)

Answer 14

• Unit cells arrange to form crystal lattice.
• Ideal crystals: Infinite periodic spatial sequences of identical structural elements.
• Real crystals: Microcrystaline, keep their identical spatial sequence only in microscopic scale and instead have various sizes and orientations in structure.
• Defects: Point defect, Line defect, Surface defect

Question 15

Optical properties of crystalline materials

Answer 15

Anisotropic, their physical properties are dependent on direction of measurement related to orientation of atoms in the crystal.

Question 16

Thermotropic liquid crystals

Answer 16

Liquid crystal: Substance that possesses properties of both liquid and crystalline solid.
- Transitional order (Center mass point forms plane), Orientational order (axes of molecule align parallel)
Thermotropic: Order of structure depends on temperature.
- Applied to contact tomography: Changing colors of film on patients body indicates inflammation (higher temp, different color)

Question 17

Lyotropic liquid crystals

Answer 17

• Order is affected by concentration of components
• Components are amphiphilic molecules that form ordered structures in presence of solvent
• Phospholipids

Question 18

Energy levels of electrical insulators

Answer 18

• Insulators have valence band and conduction band
• Gap between bands called forbidden band
• Electrons are not able to cross it to get to conduction band

Question 19

The function of the semiconductor diode.

Answer 19

• Acts as one way valve for electricity
• n and p type semiconductors
• In semiconductors increasing temperature gives more energy for electrons to reach conductance band so therefore more conductance.

Question 20

Energy levels of electrical conductors.

Answer 20

• Conduction and valence band only
• No forbidden band
• Increasing temp here causes vibration which disturbs electron flow.

Question 21

The liquid state

Answer 21

• Lacks spatial order of solid
• Isotropic, no directional dependence
• Take shape of container
• Not compressible

Question 22

Electro- and thermo optical phenomena in liquid crystals

Answer 22

• Electro: Nematic liquid crystal (characterized only by orientation). Orientation can be controlled by electric field, manipulates optical transmission. Can be used to manufacture displays.
• Thermo: Choleric liquid crystal (twisted nematic) color of layer will change with different temperature. Contact thermography.

Question 23

Energy levels of intrinsic semiconductors

Answer 23

• There is valence band and conduction band
• Gap between them so electrons cant pass freely
• But not too big of a gap so that excited electrons can cross into conduction band
• electricity conducted!

Question 24

Types of doped semiconductors

Answer 24

• P-type (boron, acceptor, holes)
• N-type (Phosphorus, donor, electrons)