THERMOOOOOO

Question 1

system

Answer 1

A quantity of matter or a region in
space chosen for study.

Question 2

surroundings

Answer 2

The mass or region outside the
system (we do our measuring in the
surroundings)

Question 3

Boundary

Answer 3

The real or imaginary surface that
separates the system from its
surroundings.
The boundary of a system can be
fixed or movable.

Question 4

Closed system

Answer 4

Closed system (Control mass): matter can not go in
and out of the system
A fixed amount of mass, and no mass can cross its boundary.
But volume can be changed.

Question 5

Open system

Answer 5

Open system (control volume): matter can go in and out the
system
Both mass and energy can cross the boundary of a control volume.
such as a compressor, turbine, or nozzle.

Question 6

Isolated system

Answer 6

➢ An isolated system is a general system where
no mass, heat or work may cross the boundaries.
➢ An isolated system is a closed system with no energy crossing
the boundaries.

Question 7

Property

Answer 7

Any observable macroscopic characteristic of a
system.

Question 8

Intensive properties:

Answer 8

Independent of the mass of a system, such as
temperature, pressure, and density.

Question 9

Extensive property

Answer 9

Those whose values depend on the size—or
extent—of the system: total mass, total volume

Question 10

Specific property

Answer 10

Extensive properties per unit mass

Question 11

State

Answer 11

: condition of system defined by properties

Question 12

State postulate

Answer 12

• The state of a simple
  compressible system is
  completely specified by two
  independent, intensive
  properties.

Question 13

Simple compressible system

Answer 13

If a system involves no electrical, magnetic, gravitational, motion, and surface tension effects.

Question 14

Equilibrium (mech, phase, thermal)

Answer 14

In an equilibrium state there are no unbalanced potentials (or driving forces) within the
system.

Mech no pressure change
, phase no phase change, thermal all same temp throughout

Question 15

Process path cycle

Answer 15

Process:
Change from State 1 to state 2
Path:
The series of states through which a system passes during a
process.
31
Cycle:
A process during which the initial
and final states are identical.

Question 16

Iso

Answer 16

Isothermal process:
A process during which the temperature T
remains constant.

Isobaric process:
A process during which the pressure P
remains constant.

Isometric : no V change

Question 17

Diabatic vs adiabatic system

Answer 17

Dia -> E allowed in and out, (thermal contact w surroundings)

Question 18

Endo vs exothermic process

Answer 18

Endo absorbs heat exo releases

Question 19

Steady flow state

Answer 19

Steady fluid flow through a control volume
* Total volume, mass, and energy are constant
* Properties at any one point are constant
* Distribution of properties may be non-uniform

Question 20

Abs, gauge and vacuum pressure

Answer 20

Absolute pressure:
The actual pressure at a given position. measured relative to absolute vacuum (i.e., absolute zero pressure).

Gauge pressure: The difference between the absolute pressure
and the local atmospheric pressure.

Vacuum pressures: Pressures below
atmospheric pressure.

Question 21

Internal energy

Answer 21

Internal energy, U: The sum of all the microscopic forms of
energy-It comes from the total kinetic and potential energy of
molecules which composes the system (thermal, chem, nuclear, elec, magn)

Question 22

2 thermal energies

Answer 22

Sensible energy: The portion of
the internal energy of a system
associated with the kinetic energies
of the molecules.

Latent energy: The internal energy
associated with the phase of a
system.

Question 23

Chem E

Answer 23

Chemical energy: The internal
energy associated with the atomic
bonds in a molecule.

Question 24

Nuclear Energy

Answer 24

Nuclear energy: The tremendous
amount of energy associated with
the strong bonds within the nucleus
of the atom itself.

Question 25

What are the internal energy types

Answer 25

sensible, latent, chem, nu

Question 26

Mechanical energy

Answer 26

Mechanical energy: The form of energy that can be converted to mechanical work completely and directly by an ideal mechanical device such as an ideal turbine.

Question 27

Heat

Answer 27

Heat: energy transfer as a result of difference in temperature between system and surroundings. - no phase change (from high to low temp)

Question 28

Latent heat

Answer 28

The amount of energy absorbed or released during a phase-change process latent heat of fusion: the amount of energy absorbed during melting is called the and is equivalent to the amount of energy released during freezing. latent heat of vaporization is equivalent to the energy released during condensation

Question 29

Work

Answer 29

Work: energy transfer due to other than a ΔT, W -e.g. force over distance

Question 30

Conduction

Answer 30

Conduction: The transfer of energy from the more energetic particles of a substance to the adjacent less energetic ones as a result of interaction between particles (touching).

Question 31

Convection

Answer 31

Convection: The transfer of energy between a solid surface and the adjacent fluid that is in motion, and it involves the combined effects of conduction and fluid motion. The faster the fluid motion, the greater the heat transfer.

Question 32

Radiation

Answer 32

Radiation: The transfer of energy due to the emission of electromagnetic waves (or photons).

Question 33

Electrical work

Answer 33

The generalized force is the voltage (the electrical potential) and the generalized displacement is the electrical charge.

Question 34

Magnetic work

Answer 34

The generalized force is the magnetic field strength and the generalized displacement is the total magnetic dipole moment.

Question 35

Electrical polarization work

Answer 35

The generalized force is the electric field strength and the generalized displacement is the polarization of the medium

Question 36

Mechanical forms of work

Answer 36

Shaft work, spring work, elastic work, stretching of liquid film, kinetic or potential work

Question 37

Zeroth law

Answer 37

For 3 systems, A, B and C, that are all adiabatically enclosed, if A is in thermal equilibrium with B which is also in equilibrium with C then A must be in thermal equilibrium with C

Question 38

First law of thermodynamics

Answer 38

energy can be neither created nor destroyed during a process; it can only change forms.

Question 39

Energy balance

Answer 39

The net change (increase or decrease) in the total energy of the system during a process is equal to the difference between the total energy entering and the total energy leaving the system during that process

Question 40

Sign convention heat transfer work

Answer 40

Heat transfer to a system and work done on a system are positive; heat transfer from a system and work done by a system are negative.

Question 41

Pure substance

Answer 41

substance having a fixed chemical composition throughout * Single chemical element/compound * Homogeneous mixture of various chemical elements or compounds (air) * A mixture of two or more phases of a pure substance

Question 42

Compressed/subcooled liquid

Answer 42

liquid not about to vaporize

Question 43

Saturated liquid

Answer 43

liquid about to vaporize

Question 44

Saturated liquid-vapour mixture

Answer 44

liquid and vapour phases coexist

Question 45

Saturated vapour

Answer 45

last drop of liquid just vaporized or vapour about to condense

Question 46

Superheated vapour

Answer 46

vapour not about to condense, temperature of the vapour rises

Question 47

Saturation temperature

Answer 47

temperature at which a pure substance changes phase

Question 48

Saturation pressure

Answer 48

pressure at which a pure substance changes phase

Question 49

Specific heat

Answer 49

Energy required to raise the temperature of a unit mass of a substance by one degree.

Question 50

conservation of mass principle

Answer 50

Mass, like energy, is a conserved property, and it cannot be created or destroyed during a process.

Question 51

Control volumes

Answer 51

Control volumes: Mass can cross the boundaries, and so we must keep track of the amount of mass entering and leaving the control volume.

Question 52

Steady flow process

Answer 52

the total amount of mass contained within a control volume does not change with time (mCV = constant).

Question 53

Carnot principles

Answer 53

1. The efficiency of an irreversible heat engine is always less than the efficiency of a reversible one operating between the same two reservoirs. 2. The efficiencies of all reversible heat engines operating between the same two reservoirs are the same.

Question 54

Reversible vs irreversible processes

Answer 54

Reversible (Ideal) process Can be completely reversed with no net effect on its surroundings * Final state = initial state for system, surroundings Irreversible (real) process * If the system and surroundings cannot be returned to their respective original states without leaving any trace on the surroundings * Final state = initial state for system * Final state ≠ initial state for surroundings

Question 55

Clausian statement (2nd law)

Answer 55

It is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a lowertemperature body to a higher-temperature body.

Question 56

Kelvin-Planck statement (2nd law)

Answer 56

It is impossible for a cyclic device to exchange heat with a single reservoir and produce a net amount of work.

Question 57

Second law

Answer 57

Heat always moves from hotter objects to colder objects,

Question 58

Major uses of second law

Answer 58

1. may be used to identify the direction of processes. 2. energy has quality as well as quantity. 3. used in determining the theoretical limits for the performance of commonly used engineering systems, (heat engines and refrigerators)

Question 59

Reservoir

Answer 59

Body with large thermal energy capacity that can supply or absorb heat with no noticeable change in temperature Source: Reservoir that supplies energy as heat Sink: Reservoir that absorbs energy as heat

Question 60

Heat engine

Answer 60

device that converts heat to work. * Receives heat from high-temperature source (solar energy, oil furnace, nuclear reactor, etc.) * converts part of this heat to mechanical work (e.g. shaft work) * Rejects the remaining waste heat to a low- temperature sink (the atmosphere, rivers, etc.). * Operates on a cycle.

Question 61

Refrigerators

Answer 61

device that transfers heat from a low- temperature medium to a high-temperature

Question 62

Refrigerant

Answer 62

The working fluid that is used in the refrigeration cycle

Question 63

Irrerversibilities

Answer 63

Factors that cause process to be irreversible (friction, unrestrained expansion, mixing of two fluids, heat transfer across a finite temperature difference, electric resistance, inelastic deformation of solids, and chemical reactions)

Question 64

Types of reversibilities

Answer 64

Internally reversible process (No irreversibilities occur within the system boundary during the process, Quasi-equilibrium process) Externally reversible: No irreversibilities occur outside the system boundary. (Heat transfer across infinitely small temperature difference) Totally reversible or simply reversible process: No irreversibilities within the system or its surroundings. (no heat transfer through a finite temperature difference, no nonquasi-equilibrium changes, and no friction or other dissipative effects)

Question 65

Ideal gas characteristics

Answer 65

gas particles = negligible volume in comparison with overall gas volume. equally sized and do not have intermolecular forces (attraction or repulsion) with other gas particles. move randomly in agreement with Newton’s Laws of Motion. perfect elastic collisions with no energy loss.

Question 66

Carnot heat-engine

Answer 66

most efficient heat engine (totally reversible)

Question 67

Clausius inequality

Answer 67

The cyclic integral deltaQ/T is always less than or equal to zero (equal for totally reversible) spontaneous systems heat flows from hot to cold

Question 68

Entropy characteristics

Answer 68

State property (Dec if heat removed from syst. Inc if heat added) Entropy change can be negative during process, butt entropy generation always + (due to irreversibilities)

Question 69

Pure substance

Answer 69

substance having a fiexd chemical composition throughout (sing element/mol, homogenous mixture of various ele/mol, 2 or more phases of pure sub)

Question 70

Flow work

Answer 70

Flow work, also known as "flow energy" or "displacement work", is the work done by a fluid as it flows through a control volume, pushing a piston or turning a turbine. W=PV

Question 71

Boundary work

Answer 71

Boundary work, also known as "pressure-volume work" or "mechanical work", is the work done by a system as it changes its volume while exerting a pressure against a boundary, such as a piston or a wall. int(PdV)