Thermo 1 Definitions

Question 1

Thermodynamics

Answer 1

The science fo the relationship between heat and mechanical work

Question 2

Closed System

Answer 2

A system in which no mass crosses the system boundary

Question 3

State postulate

Answer 3

In a simple equilibrium, a system can be described by just two properties, thereby fixing the other four.

Question 4

Simple system

Answer 4

Only one chemical component, existing in one physical state

Question 5

Gauge pressure

Answer 5

Pressure above atmospheric pressure

Question 6

Absolute pressure

Answer 6

Pressure measured using zero as a datum

Question 7

Zeroth Law

Answer 7

If A is in equilibrium with both B and C, it follows that both B and C are in equilibrium

Question 8

Process

Answer 8

Transforms a system from one equilibrium to another

Question 9

Quasi-equilibrium process

Answer 9

A process that is very close to equilibrium along a path

Question 10

Stationary system

Answer 10

A system where changes in KE or PE are small

Question 11

Internal Energy

Answer 11

The combination of all microscopic forms of energy in a fluid

Question 12

Cycle

Answer 12

A closed system undergoes a cycle when it passes through a series of events which leaves its final state equal to all aspects of its initial state

Question 13

Property

Answer 13

Characteristics used to describe an object and is independent of path - temperature, pressure, volume, enthalpy, entropy, internal energy, density

Question 14

Pressure

Answer 14

Force per unit area exerted on a boundary

Question 15

Two-point temperature scale

Answer 15

A scale using two reference temperatures - eg celcius

Question 16

Thermodynamic temperature scale

Answer 16

No dependence on the behaviour of a substance - eg kelvin

Question 17

Path

Answer 17

How the system is transformed during a process

Question 18

Work

Answer 18

The product of a force and the distance over which the force is applied

Question 19

First Law

Answer 19

When a closed system is taken through a cycle, the work delivered to the surroundings is equal to the net heat taken from the surroundings

Question 20

Axiom

Answer 20

A statement that cannot be proved, but no cases exist to disprove it.

Question 21

First Law - corollary 1

Answer 21

There exists a property of a closed system such that a change in its value is equal to the difference between the heat supplied and the work done during any change of state

Question 22

First Law - corollary 2

Answer 22

The internal energy of a closed system remains unchanged if the system is isolated from its surroundings

Question 23

First Law - corollary 3

Answer 23

A perpetual motion machine of the first kind is impossible - one which produces work without the supply of heat.

Question 24

Equilibrium

Answer 24

All driving forces on a system are balanced

Question 25

Intensive properties

Answer 25

Properties which have no dependence on the size of a system (temperature, specific volume, density, pressure, etc)

Question 26

Extensive properties

Answer 26

Properties that depend on the size of a system (V, m, etc)

Question 27

Non-Flow Energy Equation

Answer 27

ΔU=Q+W. Derived from the 1st corollary of the first law.

Question 28

Specific heat capacity

Answer 28

The quantity of energy required to raise the temperature of a unit mass by one degree at constant volume/pressure.

Question 29

Enthalpy

Answer 29

A combination property, comprising internal energy and flow work. H = U+pV

Question 30

Isolated system

Answer 30

A system where no mass, heat or work crosses the system boundary

Question 31

Isochoric

Answer 31

Constant volume process

Question 32

Isobaric

Answer 32

Constant pressure process

Question 33

Isothermal

Answer 33

Constant temperature process

Question 34

Isentropic

Answer 34

Constant entropy process - no heat transfer from surroundings

Question 35

Isentropic relationship

Answer 35

pV^γ = constant

Question 36

Polytropic process

Answer 36

pV^n = constant

Question 37

Steady flow process

Answer 37

A process with a continuous flow of mass

Question 38

Kelvin-Planck Statement of the Second Law

Answer 38

It is impossible for any device that operates on a cycle to receive heat from a single reservoir and produce an amount of work.

Question 39

Clausius Statement of the Second Law

Answer 39

It is impossible to construct a device that operates in a cycle and transfers heat from a cooler to a hotter body without work being done on the system by the surroundings.

Question 40

Reservoir

Answer 40

A very large heat store whose temperature changes only infinitesimally when heat is added or rejected

Question 41

Source

Answer 41

Hot reservoir

Question 42

Sink

Answer 42

Cold reservoir

Question 43

Perpetual motion machine of the second kind

Answer 43

A cyclic engine connected to one reservoir only and producing work

Question 44

Corollary 1 of the Second Law

Answer 44

It is impossible to construct a device that operates in a cycle and transfers heat from a cooler to a hotter body without work being done on the system by the surroundings. (Clausius statement)

Question 45

Reversible

Answer 45

A process in which both fluid and surroundings can be restored to their original states

Question 46

Isentropic efficiency

Answer 46

The ratio of real-world work to reversible work

Question 47

Corollary 2 of the Second Law

Answer 47

It is impossible to construct an engine operating between only two reservoirs which will have a higher efficiency than a reversible engine operating between the same two reservoirs

Question 48

Corollary 3 of the Second Law

Answer 48

All reversible engines operating between the same two reservoirs have the same efficiency

Question 49

Clausius Inequality (Corollary 6)

Answer 49

cyclic int(dQ/T) <= 0

Question 50

Adiabatic

Answer 50

No heat transfer across the system boundary

Question 51

Closed cycle

Answer 51

Working gas is recirculated around the engine

Question 52

Open cycle

Answer 52

Gas enters and leaves the engine

Question 53

Compression ratio

Answer 53

r = Vmax/Vmin