thermodynamics Flashcards
The amount of heat absorbed when CO2 gas reacts with a solid CaO to form solid CaCO3 is measud in a bomb calorimeter. The data obtained give a direct measure of
delta U
It is defined as the fraction of 1/273.16 of the temperature of the triple point of water.
kelvin
Heat required to raise the temperature one pound mass of a substance by degree Farenheit
BTU
Which of the following physical quantities is NOT conserved in a given process
a. momentum. b.energy. c. electric charge. d.entropy
entropy
During adiabatic expansion of an ideal gas, work is done by the system and its internal energy
decreases
All of the following have standard enthalpy of formation values equal to zero at 25 deg C EXCEPT
a. Cl2(g). b. O2(g). c. Na(g). d. N2(g)
Cl2 (g)
The work that may be performed on a system is _______ when the opposing pressure differs only infinitesimally from the internal pressure of the gas itself
minimum
A sample of an ideal is allowed to escape reversibly and isothermally into a vacuum
W=Q=DeltaU=0
A thermodynamic cycle that operates two isothermal and two isentropic processes
Carnot Cycle
The natural flow of heat is described in the statement of
Clausius
If the forward reaction is observed to be spontaneous, which of the ff is possible if its reverse reaction is spontaneous at high temperature?
a. deltaH (+) and delta S (+). c. deltaH (-) and delta S (-)
b. deltaH (+) and delta S (-). d.deltaH (-) and delta S (+)
c. deltaH (-) and delta S (-)
The thermal efficiency is greatly influenced by compression ratio and the specific heat ratio of the working fluid.
Otto Cycle
In rankine cycle, the condition of steam leaving the turbine could be any one of the ff EXCEPT
a. superheated vapor. c. L-V mixture
b. saturated vapor. d. saturated liquid
d. saturated liquid
A physical science that deals with the study of the interrelation of various forms of energy. It is concerned with the transfer of heat and work in various physical and chemical processes.
Thermodynamics
portion of the universe under consideration.
System
Three types of thermodynamics system
- Open system
- Closed system
- Isolated system
It is also called control volume which allows transfer of both matter and energy.
Open system
A type of system that allows neither transfer of matter nor energy.
Isolated system
A type of system also kown as control mass which allows exchange of energy only, consists of a fixed amount of mass while its volume does not have to be fixed.
Closed system
A portion of the universe other than the system.
Surroundings
real/imaginary or fixed/moving surface that separates the system from its surroundings and where exchange of matter or energy takes place.
Boundary
A thermally-conducting boundary in which a change of state is observed even through two objects of different temperatures are brought into contact.
Diathermic boundary
A thermally-insulating boundary in which a change of state is observed even through two objects at different temperatures are brought into contact.
Adiabatic boundary
A state in which the properties of the system does not vary with time. The system is uniform where there is no internal temperature, psssure, concentration or velocity gradient.
equilibrium state
State that exist between two subsystems of equal pressure.
Mechanical equilibrium
The net flows of heat, mass or work between the system and its surroundings is zero and the net rate of all chemical reactions is zero,
Equilibrium state
State that exist between two subsystem of equal temperature.
thermal equilibrium
any change that undergoes whithin a system that causes shift from one equilibrium state to another.
Process
a sufficient slow process that allows the system to internally adjust so that the properties in one part does not change faster than other parts.
Quasi-static or quasi-equilibrium process
process where a fluid flows through a control in volume and the fluid properties can change from point to point within the control volume.
steady-flow process
A thermodynamic process in which the net rate of heat transfer to and from the system is zero.
Adiabatic or isocaloric process
Process that occurs at constant temperature.
Isothermal process
Process that occurs at constant pressure.
Isabaric process
Process that occurs at costant volume.
Isochoric or isometric process
functions that depends on the current state of the system and not on how the system reaches that state.
State or point functions
Functions that depend on the path followed during a process.
Path functions
ZerothbLaw of thermodynamics was formulated by _________
Ralph Howard Fowler (1889-1994)
“If body A is in thermal equilibrium eith body B and body B is in thermal equilibrium with body C then body A is in thermal equilibrium with body C.”
Zeroth Law of Thermodynamics
Form of energy transferred from one body to another by virtue of temperature differnce.
Heat (Q)
Process that results to the RELEASE of energy in the form of heat TO surroundings.
Exothermic process
Process that results to the ABSORPTION of energy in the form of heat FROM the surroipundings.
Endothermic process
form of energy that results in the motion of a body by virtue of an opposing force; energy transfer associated with a force acting through a distance.
Work (W)
A type of molecular mechanism of heat and work transfer which uses disorderly or random molecular motion also called thermal motion of molecules.
Transfer of energy as heat
A type of molecular mechanism of heat and work transfer which uses orderly molecular motion.
Transfer of energy as work
Refers to the energy of the system as a bulk which can be associated with the velocity and location of its center of mass.
External energy
Energy due to the translational motion of the system relative to some point of reference or to the rotation of the system about an axis.
Kinetic Energy
Energy due to the position of the system in a potential field such as electromagnetic field or gravitational field
Potential energy
this law states that “the energy of the universe is constant and can neither be created nor destroyed but can be change from one form to another.”
First (1st) Law of Thermodynamics
Refers to the total energy of the system in the molecular level which can be due to the motion of molecules relative to the center of mass of the system or to the rotational and vibrational motion.
Internal Energy (U)
Energy associated with the kinetic energy of the molecules as it moves at a certain velocity through space.
Translational kinetic energy
Energy associated with the back and forth motion of the atoms in a polyatomic molecule about their common center of mass.
Vibrational Kinetic Energy
Energy associated with the rotation of the atoms in a polyatomic molecule about an axis
Rotational Kinetic Energy
Energy associated with the rotation of the subatomic particles about their axes
Spin energy
States that the the total kinetic energy of a system is shared equally among its independent components once the system attains thermal equilibrium.
Equipartition theorem of energy
Measure of the TOTAL ENERGY of a thermodynamic system; includes energy required to create the system (U) and the energy required to make room for the system by displacing its surroundings thereby establishing its pressure (P) and volume (V)
Enthalpy
Heat involved in the formation of a compound from its element in their most thermodinamically stable state at 25 deg C and 1 bar
Standard enthalpy of formation
Heat released when one mole of a fuel was burned in the presence of oxygen gas to produce carbon diaoxide gas and liquid water at 25 deg C and 1bar
Standard enthalpy of combustion
If a reaction proceeds via several steps, the heat of the of the overall reaction is the same as the algebraic sum of the heats involved in various steps.
Hess’ law of heat summation
Describes the temperature of a fluid when it is forced to flow through a valve or porous plug adiabatcally which is known as
throttling or isenthalpic process
Is a device that increases the velocity of the fluid at the expense of pressure
Nozzle
Is a device that decreses the velocity of the fluid resulting to an increase in its pressure
Diffuser
Are devices used to increase the pressure of a fluid by the supply of work through a rotating shaft.
Compressor, fans and pumps
Are used to transport a gas by increasing its pressure slightly
Fans
Are devices capable of increasing the pressure of gases and liquids respectively
Compressor and pumps
Are devices that generate work from a flowing fluid
Turbines
Refers to any flow restricting device such as an adjustable valve, porous plug or a capillary tube
Throttling valve
