Theory

Question 1

____________ is the science relating heat and work transfers and the related changes in the
properties of the working substance. The working substance is isolated from its surroundings in
order to determine its properties.

Answer 1

Thermodynamics

Question 2

________ is the science relating heat and work transfers and the related changes in the
properties of the working substance. The working substance is isolated from its surroundings in
order to determine its properties.

Answer 2

Thermodynamics

Question 3

Collection of matter within prescribed and identifiable boundaries. A system may be
either an open one, or a closed one, referring to whether mass transfer or does not take place across
the boundary.

Answer 3

System

Question 4

Is usually restricted to those particles of matter external to the system which may
be affected by changes within the system, and the surroundings themselves may form another
system.

Answer 4

Surroundings

Question 5

A physical or imaginary surface, enveloping the system and separating it from the
surroundings

Answer 5

Boundary

Question 6

is any quantity whose changes are defined only by the end states and by the process.

Examples of thermodynamic properties are the Pressure, Volume and Temperature of the working
fluid in the system above.

Answer 6

Property

Question 7

The normal force exerted per unit area of the surface within the system. For
engineering work, pressures are often measured with respect to atmospheric pressure rather than
with respect to absolute vacuum.

Answer 7

Pressure (P)

Question 8

is the degree of hotness or coldness of the system. The absolute
temperature of a body is defined relative to the temperature of ice; for SI units, the Kelvin scale.
Another scale is the Celsius scale.

Answer 8

Temperature (T)

Question 9

The property of a system covering all forms of energy arising from the
internal structure of the substance.

Answer 9

Internal Energy (u)

Question 10

A property of the system conveniently defined as h = u + PV where u is the internal
energy.

Answer 10

Enthalpy (h)

Question 11

The microscopic disorder of the system. It is an extensive equilibrium property.

Answer 11

Entropy (s)

Question 12

is the State of the substance such as solid, liquid or gas.

Answer 12

Phase

Question 13

It is possible that phases may be mixed, eg ice + water, water + vapour etc.

Answer 13

Mixed Phase

Question 14

A _________ is a vapour whose dryness fraction is equal to zero. A saturated vapour has a quality of 100% or a dryness fraction of one.

Answer 14

Saturated State

Question 15

A gas is described as superheated when its temperature at a given pressure
is greater than the saturated temperature at that pressure, ie the gas has been heated beyond its
saturation temperature.

Answer 15

Superheated Vapour

Question 16

The difference between the actual temperature of a given vapour and the
saturation temperature of the vapour at a given pressure.

Answer 16

Degree of Superheat

Question 17

A liquid is described as undercooled when its temperature at a given pressure
is lower than the saturated

Answer 17

Subcooled Liquid

Question 18

The difference between the saturation temperature and the actual temperature
of the liquid is a given pressure.

Answer 18

Degree of Subcool

Question 19

A state point in which all solid, liquid and vapour phases coexist in equilibrium.

Answer 19

Triple Point

Question 20

A state point at which transitions between liquid and vapour phases are not clear for H2O

Answer 20

Critical Point

Question 21

A process is a _________ in which the state of the system change and some properties vary from their
original values.

Answer 21

path

Question 22

no heat transfer from or to the fluid

Answer 22

Adiabatic

Question 23

no change in temperature of the fluid

Answer 23

Isothermal

Question 24

no change in pressure of the fluid

Answer 24

Isobaric

Question 25

no change in volume of the fluid

Answer 25

Isochoric

Question 26

no change of entropy of the fluid

Answer 26

Isentropic

Question 27

no change of enthalpy of the fluid

Answer 27

Isenthalpic

Question 28

Compressibility factor, Z, is a measure of deviation from the ideal gas. 1. FORMULA: 2. Z for an ideal gas

Answer 28

Z = PV/RT Z = 1

Question 29

The "________" states that if two systems are at the same time in thermal equilibrium with a third system, they are in thermal equilibrium with each other.

Answer 29

zeroth law

Question 30

The first law of thermodynamics is the application of the _______ principle.

Answer 30

conservation of energy

Question 31

Work performed on or by the working fluid within a syste’s boundary is defined as the summation (or integration) of the product of pressure and volume of the fluid during a process. FORMULA:

Answer 31

W = - (integral) PdV

Question 32

The _________ is a general principle which places constraints upon the direction of heat transfer and the attainable efficiencies of heat engines. It's implications may be visualized in terms of the waterfall analogy.

Answer 32

second law of thermodynamics

Question 33

“It is impossible to construct a system which when operating in a cycle will extract heat energy from a single source and do an equal amount of work on the surroundings”. Ie never possible to achieve 100% thermal efficiency

Answer 33

Kelvin -Planck Statement

Question 34

“It is impossible to construct a device which when operating in a cycle has no other effect than the transfer of heat energy from a cool to a hotter body”. Ie some work is done on or by the working fluid to the surroundings or vice versa.

Answer 34

Clausius Statement

Question 35

In 1865 ________ observed that the amount dQ/T is proper to describe the thermodynamic phenomenon. This amount was named reduced heat or entropy. During a process, the change in entropy is defined as : _________

Answer 35

Clausius dS = Q/T

Question 36

is a state variable whose change is defined for a reversible process at T where Q is the heat absorbed.

Answer 36

Entropy

Question 37

a measure of the amount of energy which is unavailable to do work.

Answer 37

Entropy

Question 38

a measure of the disorder of a system.

Answer 38

Entropy

Question 39

the entropy change in an irreversible adiabatic process leads to process efficiency. The ideal constant entropy process is termed isentropic and the ratio of the specific work transfer in the ideal process to that in the actual process is called the isentropic efficiency.

Answer 39

Isentropic Efficiency

Question 40

The entropy of a perfect crystal is zero when the temperature of a the crystal is equal to absolute zero (0 K)

Answer 40

Third Law