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MCAT Physics + Math > Ch 3 - Thermodynamics > Flashcards

Ch 3 - Thermodynamics Flashcards

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1
Q

What is the zeroth law of thermodynamics?

A

states that objects are in thermal equilibrium when they are at the same temperature
- if a=b and b=c, then a=c

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2
Q

What do objects in thermal equilibrium experience?

A

no net exchange of heat energy

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3
Q

What is temperature?

A
  • a qualitative measure of how hot or cold an object is

- quantitatively, it is related to the average kinetic energy of the particles that make up a substance

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4
Q

What is thermal expansion?

A

describes how a substance changes in length or volume as a function of the change in temperature

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5
Q

What is the difference between a system and the surrounding?

A
  • a thermodynamic system is the portion of the universe that we are interested in observing
  • the surroundings include everything that is not part of the system
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6
Q

What are the 3 types of systems?

A
  • isolated: do not exchange matter or energy with the surroundings
  • closed: exchange energy but not matter with their surroundings
  • open: exchange both energy and matter with their surroundings
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7
Q

What are state functions?

A
  • pathway independent and are not themselves defined by a process
  • pressure, density, temperature, volume, enthalpy, internal energy, Gibbs free energy, and entropy
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8
Q

What are process functions?

A
  • describe the pathway from one equilibrium state to another

- work and heat

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9
Q

What is the first law of thermodynamics?

A
  • a statement of conservation of energy: the total energy in the universe can never decrease or increase
  • an increase in U is caused by transferred heat into the system or performing work on the system
  • U will decrease when heat is lost from the system or work is performed by the system
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10
Q

What is the total internal energy of a closed system equal to?

A

the heat flow into the system minus the work done by the system
delta U = Q - W

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11
Q

What is heat?

A
  • the process of energy transfer between 2 objects at different temperatures that occurs until the 2 objects cone into thermal equilibrium (reach the same temperature)
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12
Q

What is specific heat?

A
  • the amount of energy necessary to raise one gram of a substance by one degree Celsius or one Kelvin
  • specific heat of water is 1 cal/g.K
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13
Q

What is the heat of transformation?

A
  • during a phase change, heat energy causes changes in the particles’ potential energy and energy distribution (entropy), but no kinetic energy
  • therefore, there is no change in temperature
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14
Q

What are the 4 special types of thermodynamic systems in which a given variable is held constant?

A
  • isothermal: the temperature is constant, and the change in internal energy is 0
  • adiabatic: no heat exchanged
  • isobaric: the pressure is constant
  • isovolumetric (isochoric): the volume is constant and the work done by or on the system is 0
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15
Q

What is the second law of thermodynamics?

A

states that in a closed system (up to and including the entire universe), energy will spontaneously and irreversibly go from being localized to being spread out (dispersed)

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16
Q

What is entropy?

A

a measure of how much energy has spread out and how spread out energy has become

17
Q

How do microstates relate to entropy?

A

on a statistical level, as the number of microstates increases, the potential energy of a molecule is distributed over that larger number of microstates, increasing entropy

18
Q

Are natural processes irreversible or reversible?

A
  • every natural process is ultimately irreversible
  • under highly controlled conditions, certain equilibrium process such as phase changes can be treated as essentially reversible
19
Q

How do you convert between temperature units?

A 
F = 9/5.C + 32
K = C + 273
20
Q

What is the coefficient of linear expansion?

A

deltaL = alpha.L.deltaT

constant (alpha) that characterizes how a specific material’s length changes as the temperature changes

21
Q

What is the coefficient of volumetric expansion?

A

deltaV = beta.V.deltaT

a constant that characterizes how specific material’s volume changes as the temperature changes

22
Q

What is the maximum distance that 2 object can be from one another and still adhere to the zeroth law of thermodynamics?

A
  • there is no set distance

- as long as the 2 objects are in thermal contact and at the same temperature, they are in thermal equilibrium

23
Q

What does a negative or positive change in internal energy mean?

A
  • neg: decreasing temperature

- pos: increasing temperature

24
Q

What does a negative or positive heat mean?

A
  • neg: heat flows out of the system

- pos: heat flows into the system

25
Q

What does a negative or positive work mean?

A
  • neg: work is done on the system (compression)

- pos: work is done by the system (expansion)

26
Q

How much heat is required to raise 1 g of water by 1 C?

A
  • 1 calorie (cal)
  • 1 Calorie needed to raise 1 kg of water by 1C
    1 Cal = 1000 cal = 4184 J
27
Q

What is conduction?

A

the direct transfer of energy from one molecule to another through molecular collisions

28
Q

What is convection?

A

the transfer of heat by the physical motion of a fluid over a material

29
Q

What is radiation?

A

the transfer of energy by electromagnetic waves

30
Q

What equation relates heat gained or lost by an object and the changes in temperature of that object?

A

q = mcdeltaT

31
Q

How do you calculate heat energy of a phase change?

A

q= mL

L is the heat of transformation (latent heat)

32
Q

What are the terms for the following:

  • solid to liquid
  • liquid to solid
  • liquid to gas
  • gas to liquid
  • solid to gas
  • gas to solid
A
  • s>l = fusion or melting
  • l>s = freezing or solidification
  • l>g = boiling, evaporation, or vaporization
  • g>l = condensation
  • s>g = sublimation
  • g>s = deposition
33
Q

How is entropy calculated?

A

deltaS = Qrev/T –> J/mol.K

34
Q

What is the relationship between entropy of a system and its surroundings for any given thermodynamic process?

A
  • Suniverse = Ssystem + Ssurroundings > 0
  • entropy of the isolated system and surroundings will never decrease; either remain 0 or increase
  • entropy of a system can decrease as long as the entropy of its surroundings increased by at least as much

MCAT Physics + Math (12 decks)

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