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*Thermodynamics > Intro and Terminology (Ch. 1) > Flashcards

Intro and Terminology (Ch. 1) Flashcards

1
Q

What is Thermodynamics?

A
  • a realistic study of how stuff works
  • the study of energy and its conversions

Def: science of the relationship between heat, work, temperature, and energy. In broad terms, thermodynamics deals with the transfer of energy from one place to another and from one form to another.

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2
Q

What is Energy?

A
  • the capacity to do work
  • power efficiently exerted

can exist in a variety of forms (electrical, mechanical, chemical, thermal, or nuclear), and can be transformed from one form to another

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3
Q

What is heat?

A

energy flow across a system boundary due to a temp. difference

  • latent
  • sensable

(can’t store heat, think of it as water flow)

Def: A form of energy associated with the kinetic energy of atoms or molecules and capable of being transmitted through solid and fluid media by conduction, through fluid media by convection, and through empty space by radiation.

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4
Q

What is Work?

A

energy flow across a system boundary due to mechanical motion

Def: the product of a force applied, and the distance through which that force acts.

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5
Q

What does it mean to say that heat and work are transient?

A
  • they are moving

- energy in transit

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6
Q

Can energy be stored?

A

yes

  • internal Energy
  • potential E
  • kinetic (store E in motion to apply greater F eg. football player)
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7
Q

What is the conservation of energy?

A

a principle stating that energy cannot be created or destroyed, but can be altered from one form to another. (energy is dissipated but not lost)
- sum E = 0

(never been violated … yet)

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8
Q

What is the 1st Law of Thermodynamics?

A

states that heat is a form of energy, and thermodynamic processes are therefore subject to the principle of conservation of energy. This means that heat energy cannot be created or destroyed.

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9
Q

What is the 2nd Law of Thermodynamics?

A

states that the total entropy of an isolated system can never decrease over time. … In all spontaneous processes, the total entropy always increases and the process is irreversible. (energy is dissipated, only entropy is not conserved)

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10
Q

What are some consequences of the 2nd Law of Thermodynamics?

A
  • Gives a direction - things always proceed in direction of dissipation (entropy creation) [eg. smoke, dispersion of a dye in water]
  • Undissipated energy is worth more than dissipated energy
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11
Q

What is a system?

A
  • the part of the universe we are interested in

- whatever we want to study

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12
Q

What are the surroundings?

A
  • universe minus the system

- everything external to the system

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13
Q

What is the system boundary?

A
  • separates the system from the surroundings (may be at rest of in motion)
  • aka: control surface
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14
Q

What are the two basic types of systems?

A
  • closed systems

- control volume systems

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15
Q

What is a closed system?

A

system with a fixed quantity of matter

aka. control mass system
- exchanges Energy but not mass with surroundings (eg. a piston cylinder)

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16
Q

What is a control volume system?

A

a region of space through mass may flow

aka. open system
- exchanges both mass and Energy with surroundings (eg. a pump)

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17
Q

Compare system terminology:

A

control mass = closed system
control volume = open system
control surface = system boundary

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18
Q

What is an Isolated system?

A

a special type of closed system that does not interact in any way with surroundings
- exchanges neither Energy nor mass with surroundings (eg. gas trapped inside a closed, rigid, insulated container)

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19
Q

What is a property of a system?

A

a macroscopic characteristic of a system (to which a numerical value can be assigned at a particular time without knowing the previous behavior/history of the system)
- mass, volume, energy, pressure, temperature

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20
Q

What is the state of a system?

A

the condition of a system as described by its properties

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21
Q

What is a process?

A

a change in the state of a system caused by a change in any of its properties.
(a transformation from one state to another)

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22
Q

What is a steady state?

A

a system in which none of its properties changes with time

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23
Q

What is a test for determining if a quantity is a Property?

A

A quantity is a property IFF its change in value between the two states is independent of the process

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24
Q

What are the two general classes of properties?

A

Extensive properties

Intensive properties

25
Q

What are Extensive properties?

A
  • Total value = sum of parts
  • depend on size of system (if cut in half property changes)
  • can vary only with time
  • eg. mass, volume, total Energy
    (not useful for solving problems)
26
Q

What are Intensive properties

A
  • apply at a point and are independent of the size of a system (not additive, remains same if matter cut in half)
  • function of position and time (can vary from place to place)
  • eg. specific volume, density, pressure, temperature
27
Q

What is a “specific” property?

A

an Intensive property that is on a “per unit mass” basis
- helps to relate intensive properties to extensive properties
(expressions for the 1st and 2nd Laws of Thermodynamics will be written in terms of extensive properties and the charts we use to look up property values will contain intensive properties)

28
Q

How many properties can we specify before nature fixes the values of the rest of them?

A

2 - “For a pure substance existing in the form of a single phase (solid, liquid or gas), specifying the values of any two intensive variables will fix the values of all of the others.”

29
Q

What is a phase of matter?

A

matter forming a homogenious physical structure

- solid, liquid, gas, (also: plasma, Bose-Einstein Condensate)

30
Q

What is a pure substance?

A

Matter with a single atomic or molecular species

31
Q

What is the concept of Equilibrium?

A

A condition of balance maintained by an equality of opposing forces (mechanics def), and a balance of other influences (Thermodynamics def)
- several types of equilibrium (mechanical, thermal, phase, and chemical) must exist individually to have complete equilibrium

32
Q

How can you determine if a system is in thermodynamic equilibrium?

A

Isolate the system and watch for changes in its properties. If no changes, then system was in equilibrium at moment it was isolated.

33
Q

What are the primary dimensions?

A
  • mass (mechanics)
  • length (mechanics)
  • time (mechanics)
  • Temperature (thermodynamics)
  • electric power (electricity)
34
Q

What is the Continuum Hypothesis?

A

an idealization of matter from the macroscopic perspective in which the description of matter is simplified by considering it to be distributed continuously throughout a region

35
Q

What is the importance of being able to treat substances as continua?

A

-when substances can be treated as continua, their intensive thermodynamic properties can be referred to “at a point” (see p. 13)

36
Q

What is the specific volume?

A

the volume per unit mass (reciprocal of the density

37
Q

What is a mole?

A

an amount of a given substance numerically equal to its molecular weight (M)
- just a way to count things
n (kmol) = m (kg)/ M (kg/kmol) [gives n in gram moles (mol)]

38
Q

How many molecules are in a gram mole (mol)?

A

6.022 x 10^23 [Avogadro’s number]

39
Q

How do you know that a property is on a molar basis?

A

signified by a bar over the symbol
- has units of the kilomole (kmol) or the pound mole (lbmol)
n (kmol) = m (kg)/ M (kg/kmol) [gives n in gram moles (mol)]

40
Q

What is pressure? What are its units?

A
  • force over unit area

F/A = N/m^2 = 1Pa (pascal)

41
Q

What is absolute pressure?

A

pressure with respect to the zero pressure of a complete vacuum
- lowest possible value is 0
P(abs) = P(gauge) + P(atm)

42
Q

What is relative pressure?

A

pressure relative to atmospheric pressure (ie. gauge pressure)

43
Q

A negative pressure (or temperature) reading must be on which type of scale?

A

Relative pressure scale (can’t get below zero absolute)

44
Q

Define and give units of: velocity (v)

A

change in position over time

v=dx/dt [=] m/s

45
Q

Define and give units of: acceleration (a)

A

change in velocity over time

a=dv/dt [=] m/s^2

46
Q

Define and give units of: force (F)

A

mass * acceleration (Newton’s 2nd Law of motion)

F=ma [=] kg m/s^2 = N (newton)

47
Q

Define and give units of: pressure (P)

A

force per unit area

P [=] N/m^2 = Pa (Pascal)

48
Q

Define and give units of: length

A

the distance light travels in a vacuum in 299792455(10^-1)s

[=] meters (m)

49
Q

Define and give units of: time

A

Cesium-133 goes from high Energy state to low energy state about 9 billion times
[=] seconds (s)

50
Q

Define and give units of: mass

A

currently defined as the mass of a standard titanium object in a vault in France, but new definition based on Avogadro’s number coming soon.
[=] kilogram (kg)

51
Q

Define and give units of: Energy

A 
KE = (m*v^2)/2 [=] (kg*m^2)/s^2 = N*m = 1J (Joule)
PE = mgh [=] (kg*m^2)/s^2 = N*m = J (Joule)
52
Q

Define and give units of: Work

A

Force times distance

integral F dx [=] N*m = J (Joule)

53
Q

Define and give units of: Power

A

Energy over time (rate of energy)

[=] J/s = W (watt)

54
Q

Is kilowatt hours a measure of power or energy?

A

Energy (J/s)*(s)=J

55
Q

What is the SI unit of pressure and stress?

A

the pascal 1 Pa = 1 N/m^2

56
Q

What are conversions for 1 atm?

A

= 1.01325 x 10^5 Pa = 1.01325 bar
= 14.696 psi
= 760 mmHg

57
Q

What is the gauge or vacuum pressure?

A

the magnitude of the difference between the absolute pressure within a system and the absolute atmospheric pressure .

58
Q

What is the 0th Law of Thermodynamics?

A

when two objects are each in thermal equilibrium with a third object then they are in thermal equilibrium with as well. (assumed in every measurement of T, 3rd object is thermometer)

59
Q

What are two thermometric properties that change with temperature?

A

Volume and electrical restistance

*Thermodynamics (4 decks)

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