Thermodynamics

Question 1

What is a thermodynamic system?

Answer 1

a region of space denoted by boundires containing a quantity of matter

Question 2

Definition of a closed system

Answer 2

contains a fixed amount of mass
work and heat can cross boundaries
boundaries are impermeable but may be movable

Question 3

Definition of an open system

Answer 3

mass can flow in and out - boundaries are permeable
work and heat can cross boundaries

Question 4

Thermodynamics Properties - convenient

Answer 4

temperature
pressure
volume
mass

Question 5

Thermodynamic Properties - Less convenient

Answer 5

Specific Volume
Density
Internal Energy
Enthalpy
Entropy

Question 6

Thermodynamic Properties - Less convenient

Answer 6

Specific Volume
Density
Internal Energy
Enthalpy
Entropy

Question 7

Types of Properties

Answer 7

Intensive
Extensive
Specific Properties

Question 8

Intensive definition

Answer 8

does not depend on the mass of the substance in a system

Question 9

Extensive properties definition

Answer 9

depends of the mass of the substance in a system

Question 10

Specific Properties definition

Answer 10

are reduced to the unit mass of a substance to acquire the meaning of intensive properties

Question 11

Process vs Cycle

Answer 11

a process is when it changes from one state to another and a cycle is where the start and end states are identical

Question 12

Isothermal process

Answer 12

constant temperature

Question 12

Isothermal process

Answer 12

constant temperature

Question 13

Isobaric Process

Answer 13

constant pressure

Question 14

isochoric process

Answer 14

constant volume

Question 15

adiabatic process

Answer 15

no heat crosses system boundries

Question 16

reversible process

Answer 16

the ideal case moves between continuous succession of equilibrium states, with no degradation of quality energy

Question 17

Irreversible process

Answer 17

all real processes, heat transfer occurring and cannot be returned, energy quality is degraded

Question 18

Process diagrams allow us to…

Answer 18

summerise whats happening in a process

Question 19

PV = constant process diagram shape

Answer 19

Concave shape

Question 20

1st law of thermodynamics

Answer 20

energy can be transferred, this can primarily accomplished by work and heat transfer

Question 21

Work

Answer 21

is done by a force when the point of force application undergoes a displacement

Question 22

Conservation of energy

Answer 22

when the total energy of an isolated system remains constant

Question 23

conservation of energy in a closed system

Answer 23

Wnet + Qnet = 0

Question 24

what does positive Wnet mean

Answer 24

means that work is done on a system by the surroundings

Question 25

Power input

Answer 25

W = W per cycle x cycle/sec

Question 26

Internal energy

Answer 26

the energy associated with the motion of molecules

Question 27

when there is no work done but heat transfer to surroundings the change of energy is...

Answer 27

the change in internal energy

Question 28

thermally insulated system

Answer 28

cannot have heat transfer across the boundary but work can take place adiabatic changes in thermal energy balance the work

Question 29

thermally isolated system

Answer 29

where to heat of work transfer can take place

Question 30

Enthalpy

Answer 30

H=U+pv

Question 31

Specific enthalpy

Answer 31

h=u+pv

Question 32

Specific Heat capacity

Answer 32

the quantity of heat required to raise the temperature of a system by 1 degree

Question 33

Heat Capacity (J/K)

Answer 33

C=dQ/dT

Question 34

Specific heat capacity equation (J/KgK)

Answer 34

C= dq/dT

Question 35

Specific heat capacity with constant volume

Answer 35

cv = dq/dT=dU/dT dq = du as there is not change in work cv= (U1-U2) / (T1-T2)

Question 36

Specific Heat Capacity with constant pressure

Answer 36

cp = dq/dt = dh/dT cp = qp/T1-T2

Question 37

heat engine works by

Answer 37

receiving heat from a hot reservoir and converts some of the heat into work it also rejects heat to the cold reservoir and work in a cycle

Question 38

what must a heat engine have ( define each )

Answer 38

heat source - supplies heat heat sink - absorbs rejected heat work output - the use of heat engines prime mover - the moving parts that deliver work

Question 39

thermal energy reservoirs

Answer 39

large bodies of heat that do not change in temperature

Question 40

thermal efficiency

Answer 40

n = W/Q

Question 41

thermal efficeincy ( 1- equation )

Answer 41

n = 1- Qout/Qin

Question 42

thermal efficeincy ( temperature equation )

Answer 42

n = 1-T1/T2

Question 43

Carnot efficiency

Answer 43

the max efficiency for a heat engine that operates reversibly between the heat source and heat sink.

Question 44

Carnot for an irreversible heat engine

Answer 44

n < ncarnot

Question 45

Carnot for reversible heat engines

Answer 45

n = ncarnot

Question 46

Carnot for impossible engines

Answer 46

n > ncarnot

Question 47

thermal resistance in heat engines

Answer 47

engine hot is a lower temperature than the heat source and engine cold is a higher temperature than the heat sink

Question 48

why is work output sometimes reduced

Answer 48

some of the work can be dissipated by heat

Question 49

LOOK AT PV DIAGRAM FOR THE HEAT SINK

Answer 49

squashed parallelogram

Question 50

Ordered energy

Answer 50

when all atoms have the same energy, they all have the same kinetic energy so move at the same speed and have the same potential energy

Question 51

Disordered energy

Answer 51

atoms move randomly and have different amounts of energy

Question 52

High Temperature vs Low temperature how disordered

Answer 52

low temp is more disordered

Question 53

Work vs Heat

Answer 53

work is ordered and heat is disordered

Question 54

Energy interactions

Answer 54

when a hot objects interacts with a cold energy moves randomly between atoms and disperses from the hot to cold

Question 55

Heat sinks output ... energy

Answer 55

ordered

Question 56

Entropy

Answer 56

S=k loge W k=1,38054x10^-23

Question 57

most disordered = ... entropy

Answer 57

highest

Question 58

work has ... entropy

Answer 58

0

Question 59

as heat disperses from hot to cold

Answer 59

the entropy increases

Question 60

entropy equation

Answer 60

change in S = Q/T

Question 61

entropy in a real process

Answer 61

Change in S system + Change in S surroundings > 0

Question 62

entropy in an ideal process

Answer 62

Change in S system + Change in S surroundings = 0

Question 63

entropy for any process

Answer 63

Change in S system + Change in S surroundings >= 0

Question 64

entropy in hot and cold sources

Answer 64

dSh = dQ/Th dSc = dQ/Tc dSh