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Thermodinamica > Lecture 3 - Properties of pure substances > Flashcards

Lecture 3 - Properties of pure substances Flashcards

1
Q

“u” stands for

A

specific internal energy

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2
Q

In thermodynamics, we are presented with problems as a function of …

A

pressure and temperature

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3
Q

“v” stands for …

A

specific volume

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4
Q

”s” stands for …

A

specific entropy

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5
Q

“h” stands for

A

specific enthalpy

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6
Q

Properties of pure substances are ..

A

P, T, s, h, u, v

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7
Q

Two phase systems are …

A

systems where liquid goes through a phase change to a vapor

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8
Q

A pure substance is one where…

A

we have fixed chemical composition throughout

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9
Q

In the solid phase, the molecules are ..

A

arranged in a 3D lattice pattern and are therefore not free to move around.

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10
Q

In the liquid phase, the molecules …

A

can move and slide over each other, but the molecules are still in a lattice pattern

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11
Q

In the gas phase …

A

the molecules are far apart from each other and are free to move about and collide.

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12
Q

In a phase change diagram, at constant pressure, the saturation temperature, Ts, is …

A

Where we go through the phase change of boiling

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13
Q

In phase change diagram, before getting to the saturation temperature, we are in the ______________ region.

A

the compressed liquid

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14
Q

At constant temperature, the saturation point is the …

A

boiling point at that pressure.

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15
Q

At the saturation point, we have a ___________.

A

saturated mixture

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16
Q

In a saturated mixture we have ….

A

both a liquid and vapor

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17
Q

In the superheated vapor region,

A

you no longer have a liquid; all you have is vapor

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18
Q

We assume the line for a superheated vapor is …

A

at a constant pressure

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19
Q

The point at which we go from compressed liquid to saturated mixture is referred to as a …

A

saturated liquid

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20
Q

The point at which we go from a saturated mixture to a superheated vapor is called ….

A

a saturated vapor

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21
Q

At boiling, we have _______, and it takes place on the ________.

A

a liquid and a vapour (liquid and vapor bubbles)

saturated mixture line

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22
Q

Bubbles forming at the bottom of a pan and floating up to the top, but no steam or turbulence at the surface of the water means that we are …

A

On the compressed liquid line

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23
Q 
compressed liquid
saturated liquid
saturated mixture
saturated vapor
superheated vapor
constant pressure
A 
líquido comprimido
líquido saturado
mezcla saturada
vapor saturado
vapor sobrecalentado/recalentado
presión constante
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24
Q

At a given (fixed) pressure, the temperature at which a pure substance changes phase is the _________.

A

saturated temperature (Tsat/Ts)

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25
Q

At the saturation temperature, a pure substances changes from ________ to ________.

A

liquid to vapor

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26
Q

The table that pertains to a pure substance changing from liquid to vapor at the saturated temperature is …

A

Tabla 3 (Propiedades del agua saturada [liquido y vapor])

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27
Q

superheated water vapor in spanish

A

vapor de agua recalentado

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28
Q

Tablas de propiedades termodinámicas del Refrigerante 134a is for …

A

saturated R134a (pg 84)

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29
Q

At a given temperature, the pressure at which a pure substance changes phase is …

A

the saturation pressure (Psat/Ps)

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30
Q

At a given temperature, the table we use for a phase change of a pure substance is …

A

Tabla 3

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31
Q

In Tabla 4, there are different pressures and for each pressure, there is a saturation temperature. This saturation temperature is the temperature at which …

A

we go through through the phase change

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32
Q

Tabla 3 is only applicable when …

A

you are going through the phase change process itself.

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33
Q

If you only have a vapor, you have to use Tabla …

A

4

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34
Q

v’, u’, h’, s’ represent ________ respectively.

A

specific volume for a saturated liquid
internal energy of a saturated liquid
enthalpy of a saturated liquid
entropy of a saturated liquid

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35
Q

v’’, u’’, h’’, s’’ represent __________ respectively.

A

specific volume for a saturated vapor
internal energy of a saturated vapor
enthalpy of a saturated vapor
entropy of a saturated vapor

36
Q

To the left of the saturated region is the ___________.

A

compressed liquid region.

37
Q

In the compressed liquid region, we ____________ a phase change process.

A

have NOT gone into a phase change process

38
Q

To the right of the two phase region, we have …

A

the superheated (sobrecalentado/recalentado) region

39
Q

In the superheated vapor region, we have …

A

increased the temperature past the saturated temperature.

40
Q

In Tabla 4, we start at the saturation temperature, and the temperature keeps increasing until …

A

the temperature at the top of the table.

41
Q

At the critical point, your …

A

saturated liquid and saturated vapor state are identical.

42
Q

At the critical point, you are …

A

at the top of the T-v diagram

43
Q

To the left of this andrews curve (∩) is the …

here ___________/
/

A

compressed liquid phase

44
Q

Inside this bell curve ∩ is the …

____here____/
/

A

liquid/vapor phase

45
Q

To the right of this bell curve ∩ is …

___________/ here
/

A

the superheated vapor phase

46
Q

________/ many of these lines on the left can pass
/ through the Andrew’s curve, and each
represents …

A

the temperature and specific volume of a liquid at constant pressure

47
Q

∩ on the curve on the left, the critical point is located …

A

at the top of the curve.

48
Q

If a fluid is heated beyond the critical point, it looks as follows:

__/ (above the bell curve.)
/ ∩ In this case, we say that we have a ..

A

supercritical fluid (fluido supercrítico)

49
Q

The critical point of a superheated fluid is …

A

the critical point of the Andrew’s curve (at the very top of the curve)

50
Q

At the critical point of a supercritical fluid, we have …

A

a critical temperature (Tcr)

51
Q

The pressure at which we have the critical point and temperature is called …

A

the critical pressure, Pcr

52
Q

∩ the left line on this bell curve is called …

A

the saturated liquid line

53
Q

∩ the right line on this curve is called …

A

the saturated vapor line

54
Q

We calculate properties for mixtures in the two phase region by …

___this region__/
/

A

v’’ - v’ ; h’’ - h’ ; s’’ - s’ ; u’’ - u’

55
Q

When performing calculations in the two phase region (where we have a liquid and a vapor), we need a way to calculate the properties because …

A

we are not at the saturated liquid point nor the saturated vapor point; we are somewhere between the two.

56
Q

We use a quantity called a quality (título) to …

A

denote where we are in a two phase region

57
Q

Quality (título) is denoted as _________ and is defined as _________.

A

X

X = mass of vapor in our system/total mass

58
Q

We have a quality (título) of 1 when we are …

A

on the saturated vapor line

59
Q

We have a quality (título) of 0 when we are …

A

on the saturated liquid line

60
Q

Quality has bounding values of …

A

0 and 1

61
Q

In the saturated liquid region, the average value of any intensive property is determined by …

A

yav = y’ + x*(y’‘-y’)

62
Q

Average enthalpy in the saturated liquid region is calculated by …

A

h = h’ + x(h’‘-h’)

63
Q

Average entropy in the saturated liquid region is calculated by …

A

s = s’ + x(s’‘-s’)

64
Q

piston cylinder device in Spanish

A

dispositivo de cilindro de pistón

65
Q

piston cylinder in Spanish

A

cilindro de pistón

66
Q

1 bar = ____ kPa

A

100

67
Q

1 m^3 = ___ dm^3

A

1000

68
Q

The mass of the liquid in a two phase region can be found by …

A

mf = volume of liquid in the problem/volume of liquid at the pressure/temperature in the Table 3

mf = vf/v’

69
Q

The mass of the vapor in a two phase region can be found by …

A

mg = volume of vapor in the problem/volume of vapor at the pressure/temperature in the Table 3

mg = vg/v’’

70
Q

Total mass is found by …

A

mf + mg

71
Q

Volume at state 1 or state 2 is found by …

A

V1 or V2 = total mass * v1 or v2

72
Q

If the volume in the table corresponds to the volume at state 1 or state 2, we can say that the volume at each state __________

A

corresponds to a saturated liquid or saturated vapor

73
Q

At constant temperature, the lines on a P-v diagram look as follows …

A

\___________

\ and passes through this bell curve, ∩

74
Q

The following lines represent ______________ on a P-v diagram:

\___________
\

A

isotherms (constant temperature lines)

75
Q

___________ can be used to relate pressure and temperature to specific volume (v), specific internal energy (u), specific enthalpy (h), and specific entropy (s) for some substances.

A

Equations of state; the ideal gas equation

76
Q

State the ideal gas equation.

A

PV = mRT

77
Q

PV = mRT; v = V/m, so from the ideal gas equation, v = …

A

v = RT/P

78
Q

The ideal gas equation only works when …

A

dealing with ideal gases
dealing with liquid/vapor mixtures at high temperature AND pressure
dealing with superheated gases at high temperature AND pressure

79
Q

THE IDEAL GAS EQUATION ONLY WORKS WHEN:

  1. liquid/vapor phases quite a ways to the right of the bell curve (at high temperature AND pressure)
  2. superheated gases way to the right of the bell curve (at high temperature AND pressure)
A

True

80
Q

Gases DO NOT deviate significantly from ideal gas behavior at states near the saturation region.

A

FALSE!

YES THEY DO!

81
Q

Gases deviate significantly from ideal gas behavior at states near the ____________ and near __________.

A

saturation region

the critical point

82
Q

We can use the ideal gas equation near the critical point or near the saturation region.

A

NO!

Gases deviate from ideal behaviour near the critical point and saturation region.

83
Q

If dealing with steam and superheated steam, it is wise to use ___________ over the ideal gas equation.

A

Tables 3 and 4

84
Q

If you need to work with the ideal gas equation close to the two-phase region, you can account for the non-ideal behavior by …

A

introducing the compressibility factor, z

using generalized compressibility charts [Figura A-1, A-2 y A-3] (if we know the critical temperature and pressure)

85
Q

The compressibility factor, z, is equal to ..

A

z = actual specific volume/ideal specific volume

86
Q

With the compressibility factor, the ideal gas equation becomes …

A

Pv = ZRT

Thermodinamica (10 decks)

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