Thermodynamics

Question 1

Define Energy

Answer 1

Energy is the capacity to do work [ J ]

Question 2

Define Work

Answer 2

Work is a form of energy which can transfer in and out of a system, stored in the organized motion of molecules [ W ]
Work is done when an object is moved against an opposing force

Question 3

What is the Work equation

Answer 3

Work = Force * Distance
OR
dW = -Pex * dV (Pex = F/A)

Question 4

Define Heat, Q

Answer 4

Energy of a system changed by means other than work [ J ]

Question 5

Define a Diabatic (Diathermic) System

Answer 5

A Diabatic system is where energy is allowed in and out in the form of heat
(system in THERMAL CONTACT with surroundings)

Question 6

Define a Adiabatic System

Answer 6

An Adiabatic System is where heat is NOT allowed in or out
(Isolated wall)

Question 7

Wsystem > 0 means:
Work done by the system on the surr
Work done on the system by the surr

Answer 7

Work done on the system by the surr

system is SELFISH likes to GAIN W&Q

Question 8

Qsystem > 0 means:
Heat transferred from system to surr
Heat transferred on the system by the surr

Answer 8

Heat transferred on the system by the surr

system is SELFISH likes to GAIN W&Q

Question 9

Define Internal energy

Answer 9

• The total energy of the system
• It is a STATE FUNCTION: depends on current state
• It is an EXTENSIVE PROPERTY: depends on amount of matter

Question 10

There must be a change in _______ for a change in internal energy

Answer 10

There must be a change in TEMPERATURE for a change in internal energy

Question 11

What is the First Law of Thermodynamics
(Internal energy equation)

Answer 11

ΔU = Q + W
(heat to system & work done on system)

Question 12

ΔU equation

Answer 12

ΔU = Ufinal - Uinitial

Question 13

2) Isobaric Process effect on ΔU = Q + W

Answer 13

Pressure is constant

ΔU = Q + W

Question 14

Isochoric Process effect on ΔU = Q+ W

Answer 14

Volume is constant
No area under curve for P/V graph, no U

ΔU = Q

Question 15

Adiabatic Process effect on ΔU = Q + W

Answer 15

No transfer of heat in the system, ΔQ = 0

ΔU = Wad

Question 16

Isothermal Process effect on ΔU = Q + W

Answer 16

Temperature is constant, ΔT = 0 ∴ ΔU

Q = -W

Question 17

Cyclic Process (e.g. engines) effect on ΔU = Q + W

Answer 17

Same initial and final stages, ΔU = 0

Q = -W

Question 18

Define a Reversible process

Answer 18

A Reversible process is never more than INFINITESIMALLY FAR from EQUILIBRIUM and an infinitesimal change in EXTERNAL conditions can REVERSE the process.

Question 19

What are Reversible Expansion conditions

Answer 19

net F = Fgas - Fex = 0

Pex = P,
Pex (external pressure)

Question 20

Define a Irreversible process

Answer 20

A Irreversible process CANNOT be reversed by a INFINITESIMAL change in EXTERNAL conditions

Question 21

What is the Ideal gas equation

Answer 21

PV = nRT

Question 22

What is the Non-ideal gas equation

Answer 22

PV = ZnRT

Z is the compressibility factor / Van Waals eq.

Question 23

What is an indicator diagram

Answer 23

P/V graph to calculate expansion work

Question 24

How to study changes in energy due to heat

Answer 24

• Calorimetry studies
• Heat capacities and enthalpies

Question 25

Define Heat capacity

Answer 25

Heat capacity is the heat required to raise the temperature of the system by one kelvin

Question 26

What does the slope of U/T graph give

Answer 26

The HEAT CAPACTIY of the system at that TEMPERATURE

Question 27

A change in internal energy can be identified with the ____ supplied at a constant volume

Answer 27

A change in internal energy can be identified with the HEAT supplied at a constant volume Qv = CvΔT

Question 28

Define Enthalpy

Answer 28

Enthalpy is the internal energy req. to CREATE a system (U) & amount of energy req. to MAKE ROOM for it (PV) Is a STATE FUNCTION => INDEP. OF PATH

Question 29

(What is the Cp and Cv relationship)

Answer 29

Cp - Cv = nR

Question 30

What changes occur when gas expands adiabatically *****SLIDE 9 L3

Answer 30

1) T= const, V increases U const 2) T reduces, V= const.

Question 31

What is the perfect gas law

Answer 31

PiVi / PfVf = Ti / Tf

Question 32

Define Standard enthalpy change

Answer 32

Is the change in enthalpy for a process in stnd states

Question 33

Define Standard state

Answer 33

Standard state is 298K and 1bar

Question 34

Define Standard enthalpy of transition

Answer 34

Standard enthalpy of transition is the enthalpy change accompanying a PHASE CHANGE in stnd states

Question 35

Define Standard reaction enthalpy

Answer 35

Is the change in enthalpy when reactants change to products in stnd states

Question 36

Define Hess' Law

Answer 36

The standard enthalpy of an overall reaction is the sum of the standard enthalpies of the individual reactions

Question 37

Define Exact Differentials

Answer 37

Exact Differentials are systems taken along a path (STATE FUNCTION)

Question 38

Define Inexact Differential

Answer 38

When a system is heated, total energy transferred as heat is sum of individual contributions along each point of the path (PATH FUCTION, DEP. ON PATH)

Question 39

Define Standard enthalpy of formation

Answer 39

Change in enthalpy for formation of compound from its CONSTITUENT ELEMENTS in their reference states.

Question 40

Define Spontaneous changes

Answer 40

Spontaneous changes are accompanied by dispersal of energy into a more disordered form

Question 41

Define Non-spontaneous changes

Answer 41

Non-spontaneous changes require something 'SPECIAL' to happen

Question 42

Define the Second Law of Thermodynamics

Answer 42

No process is possible in which the sole result is the absorption of heat from a reservoir and its complete conversion into work

Question 43

What does increasing Entropy do (2nd Law of ThermoD.)

Answer 43

Increasing Entropy increases DISORDER and RANDOMIZED MOTION

Question 44

What does negative value of entropy mean

Answer 44

Becomes less disorders, energy must be provided, NON SPONTANEOUS

Question 45

How to prove Entropy as a State Function

Answer 45

1) dQrev/Trev = 0 true for CARNOT CYCLE 2) " true for ANY SUBSTANCE 3) " true for ANY CYCLE

Question 46

What is the Carnot Cycle ***

Answer 46

1) Reversible isothermal expansion (Th) 2) Reversible adiabatic expansion (Th -> Tc) 3) Reversible isothermal compression (Tc) 4) Reversible adiabatic compression (Tc -> Th) Look up picture L6 S14

Question 47

True of any cycle L6 S20??

Answer 47

huh??

Question 48

What are the states in decreasing disorder

Answer 48

Gases > Liquids > Solids

Question 49

Define the Third Law of Thermodynamics

Answer 49

As T approaches 0, the absolute entropy tends towards zero No spatial disorder No thermal motion

Question 50

What are Third Law Entropies

Answer 50

Entropies reported on the basis that S(0) = 0, S°(T)