Thermodynamics 3 Flashcards

Terms Definitions
deltaS(surr)=-deltaH(sys)/T or
constant volume
breaking bonds
requires energy
Melting Point Depression
(-) Delta G
Ability to do work
∆v=0, so P∆V=0 (process)
the study of energy
Deflection angle
(see turning angle)
System gains energy
Positive (+)
more moles ---> less moles
Hess's Law
path-independent (cross out method)
high disorder
when entropy is +
closed system
isolated from its surroundings
crystallization can produce several crystal forms (=different MP); differ only in crystal structure, otherwise identical chemically
heat of formation for element
Temperature of Vaporization (between liquid and gas)
100 C
________________ thermometer is adopted internationally as the standard instrument for calibrating other thermometers.
Constant Volume Gas
What type of property is temperature?
formula for finding the heat measurement made in the calorimeter
transfer of heat by electro-magnetic waves
Uniform-flow process
involves the following idealization: The fluid flow at any inlet or exit is uniform and steady, and thus the fluid properties do not change with time or position over the cross section of an inlet or exit. If they do change with time, the fluid properties are averaged and treated as constants for the entire process.
The energy transferred between objects that are at different temperatures
transfer from hot to cold. Involves two objects or substances being in contact
black body radiation
characteristic spectrum of radiation produced by an opaque object that solely depends on the object's temperature.
the amount of energy (heat) required to raise the temperature of one gram of water by one Celsius degree
Change in internal energy of the system
A numeric expression of a material's thermal conductivity; the degree that heat energy can pass through a material.
a process or reaction that releases energy from the system
Stoichiometric combustion
(theoretical combustion) is the ideal combustion process during which a fuel is burned completely with theoretical air.
negative work
surroundings do work on the system
Heating Curve
Graphical depiction of the changes of state for a particular substance as heat is added to it
Irreversible Process
the system cannot return to its original state without there being a permanent change in the surroundings.
Breakdown or build things up, speed up reations by lowering the amount of activations energy needed to get the reaction going.
a system that does not exchange energy or matter with surroundings
carbohydrates and fats
have high enthalpies but combustion products have low enthalpies, making them exothermic reactions
heat capacity
thermal capacity, ratio of the change in heat energy of a unit mass of a substance to the change in temperature of the substance
State Function
Physical property that depends only on present state of system; indep. of manner in which state was prepared; ex. density, internal E, P, V, H; Z is state function if Z(B)-Z(A)=constant.
Non-Spontaneous Change
a change that does not occur naturally
Turning angle
(deflection angle) is the angle at which straight oblique shocks are deflected as flow comes upon a body, like that produced when a uniform supersonic flow impinges on a slender, two-dimensional wedge.
Stoichiometric coefficients
are the mole numbers in the stoichiometric (theoretical) reaction.
is a process, or series of processes, that allows a system to undergo state changes and returns the system to the initial state at the end of the process. That is, for a cycle the initial and final states are identical.
entropy (S)
-measure of the disorder or randomness that exists in a system
-measure of the energy in a system that is not available to do work

measure of the warmth or coldness of an object or substance
energy is not transferred to or from a system as heat. Q = 0, so change in U equals - W Work done on the system increases the system's internal energy.
Phase Change
a change from one state (solid or liquid or gas) to another without a change in chemical composition
A special type of closed system that does not ineract in any way with its surroundings is called ____________________.
Isolated system
isolated system
can have neither a transfer of energy or of matter
The energy absorbed or released during a reaction in which a substance is formed is called the
enthalpy of formation
gribbs free energy
represents the maximum work that a spontaneous reaction can preform
enthalpy of formation
the change in enthalpy for the reaction that forms 1 mole of a substance in its standard state
if ΔG is negative, ...
the forward reaction is spontaneous
Entropy generation Sgen
is entropy generated or created during an irreversible process, is due entirely to the presence of irreversibilities, and is a measure of the magnitudes of the irreversibilities present during that process. Entropy generation is always a positive quantity or zero. Its value depends on the process, and thus it is not a property.
Shock angle
is the angle at which straight oblique shocks are deflected relative to the oncoming flow as the flow comes upon a body.
Weak oblique shocks
are straight oblique shocks that have the smaller of the possible values of the shock angles for deflection angles less than the maximum deflection angle.
Polytropic process
is a process in which pressure and volume are often related by PVn= C, where n and C are constants, during expansion and compression processes of real gases.
Air-standard cycle
is a cycle for which the air-standard assumptions are applicable.
Absolute entropy
is the entropy value relative to the absolute base established by the third law of thermodynamics.
Second Law (2)
The entropy of systems are unchanged by reversible processes. The entropy of systems are increased by reversible processes.
thermodynamic free energy
amount of work that a thermodynamic system can perform
What is the equation of state?
An experimentally or theoretically derived relationship that ties the value of any one state variable (e.g. density) to the values of all the other relevant state variables (e.g. temperature and pressure). Example: α=1/ρ
The change of state from a liquid to a gas; boiling
heat of fusion
amount of energy absorbed as heat when a solid melts, phase change
H = E + PV
H = enthalpy
E = internal energy
P = pressure
V = volume
Reversible Process
A process that can be reversed in such a manner that both the system and the surrounding return to their initial conditions.
Lighting efficacy
is defined as the ratio of the amount of light output by lighting devices in lumens of light output to the electrical energy input in W.
First Law of Thermodynamics
Energy can be transformed, but cannot be created or destroyed.
When water turns to ice it
expands. ice has open-structured crystals resulting from strong bonds at certain angles that increase its volume. This makes ice less dense than water.
At equilibrium if K > 1 then lnK is +, and there will be more _________
What is thermal equilibrium?
Two (or more) objects are in contact with each other and no heat flow  i.e. they are the same temperature.
List the four conditions under which heat transfer to, or from, a system can be neglected.
Insulation, no significant temperature difference, no time, not enough surface area.
Second law of thermodynamics
-Entropy (S): The state of disorder in a system
-The entropy of a system always increases
Consequence of second law:
No system that uses energy to perform work can completely convert all the energy into useful work
Knock, or engine knock
is the audible noise occurring in the engine because of autoignition, the premature ignition of the fuel.
Back work ratio
is the ratio of the compressor work to the turbine work in gas-turbine power plants.
What is Rd vs. Rv?
Rd is the universal gas constant for dry air and Rv is the gas constant for totally moist air (100% relative humidity).
enthalpy change required to make a compound from its constituent elements
Standard enthalpy of formation is the...
Choked Rayleigh flow
occurs in a duct when a fluid can no longer be accelerated by heating above sonic velocity to supersonic velocities.
Find rate for kW hours
and determine cost for a light over night
∆G for a non spontaneous reaction
the minimum amount of work that must be preformed by an external source to make the reaction occur
Efficiency of a water heater
is defined as the ratio of the energy delivered to the house by hot water to the energy supplied to the water heater.
What is the thermodynamic definition of work?
Work is done by a system on its surroundings if the sole effect on everything external to the system could have been the raising of a weight.
Where will you have a gravity (g) larger/smaller than sea level gravity (go)?
You will have gravity smaller by 0.3% than sea level gravity at the top of the troposphere. Therefore we usually assume g~go because it is such a small difference
Specific Heat
Exothermic symbol
1 calorie
4.184 Joules
Heat of Vaporization
Spontaneous in opposite direction
A measure of order.
Combustion reactions are
always exothermic
the area being studied
Total temperature
(see stagnation temperature)
Physical characteristics.

Time Mass Length Temperature
s kg m C
lb ft F
where the enzyme preforms action
Increased electron localization of PRODUCTS results in _____ deltaG.
SI unit for measuring energy
force acting over a distance
Sonic speed
(see speed of sound)
Standard Temperature and Pressure. 273 Kelvin (0 Celsius), 1 atmosphere (760 torr, 760 mm Hg, 101.3 kPa)
Molaity (M)
M=(moles of solute)/(liters of solution)
In a closed system energy is
are everything outside the system boundaries.
Average gas constant
(see apparent gas constant)
What is qp?
heat at constant Pressure
less disorder
-ΔS ... (more or less disorder)
is an electronic device that can amplify (increase) or switch (turn on or off) electronic signals.
CAM Photosynthesis
everything occurs in teh mesophyll cycle. ex. Pineapple & Cati.
a reaction having the energy to sustain the reaction once the initial activation energy is supplied
Potential Energy
Stored Energy (stored in chemical bonds)
difference in temperature
what causes transfer of heat?
Gauge Pressure
The difference between the absolute pressure and the atmospheric pressure
is heat treated as a fluidlike substance, according to the caloric theory, that is a massless, colorless, odorless, and tasteless substance that can be poured from one body into another.
is the process of transferring energy with in a cycle from a working fluid in a high temperature in part of the cycle to a lower temperature part of the cycle to reduce the amount of external heat transfer required to drive the cycle.
Mach number
named after the Austrian physicist Ernst Mach (1838-1916), is the ratio of the actual velocity of the fluid (or an object in still air) to the speed of sound in the same fluid at the same state.
Delta H
Represents the amount of heat absorbed/released by the reaction
In a constant pressure process, enthalpy is the same as the amount of ___
heat absorbed
more disorder
if you dissolve something into a solution then ...
the transfer of heat by the movement of a fluid or gas
Ideal Gas
a hypothetical gas with molecules of negligible size that exert no intermolecular forces
Liquid water and steam form a system with two phases and can be considered as a pure substance. True or False.
The temperature of a substance is a _________ property.
the change of a substance from a liquid to a gas
Compressed Liquid
A liquid whose temperature is lower than the saturation temperature at the existing saturation pressure
What is an example of high entropy (low quality)?
Osmotic pressure
is the pressure difference across a semipermeable membrane that separates fresh water from the saline water under equilibrium conditions.
Evaporative coolers
also known as swamp coolers. Use evaporative cooling based on the principle that as water evaporates, the latent heat of vaporization is absorbed from the water body and the surrounding air. As a result, both the water and the air are cooled during the process.
Thermo-mechanical exergy
is the exergy associated with the conversion of thermal energy to mechanical energy and disregards any mixing and chemical reactions.
Gibbs phase rule
provides the number of independent variables associated with a multicomponent, multiphase system.
is the real or imaginary surface that separates the system from its surroundings. The boundary of a system can be fixed or movable.
Keq > 1
Product favored
Will proceed to the right
Heat of Formation
The heat released or absorbed (enthalpy change) during the formation of a pure substance from its elements, at constant pressure and usually denoted by ΔHf
Chemical thermodynamics
study of the interrelation of energy with chemical reactions or with a physical change of state within the confines of the laws of thermodynamics.
How/where/when does ∆z change?
Thickness of layer is directly proportional to mean virtual temperature. Can use equation to solve for height of given pressure when know temperature and surface pressure.
1st Law
If add heat to the system, you increase the internal energy of the system (you ADDED energy)
If decrease heat to the system (-Q), lose energy
Photyosystem II
makes ATP through a process called non cyclic phosphorylation.
specific heat
the quantity of heat required to raise a unit mass of homogeneous material 1°K or 1°C in a specified way given constant pressure or volume. the most common unit is J/g x C°
Energy added to the system as heat is removed from the system as work done by the system (process)
Molar heat capacity
heat, q, required to raise the temperature of 1 mole of a substance by one degree
C = q/dT
C = molar heat capacity
dT = an infinitesimally small change in temperature
Real Gas Behavior
Gas has molec. (finite size, intrinsic V), not point masses; attractive/repulsive forces required to liquefy.
Static enthalpy
is the ordinary enthalpy of the flow measured at the fluid state.
Scramjet engine
is essentially a ramjet in which air flows through at supersonic speeds (speeds above the speed of sound).
Combustion air
is dry air which can be approximated as 21 percent oxygen and 79 percent nitrogen by mole numbers. Therefore, each mole of oxygen entering a combustion chamber will be accompanied by 0.79/0.21 = 3.76 mol of nitrogen. To supply one mole of oxygen to a combustion process, 4.76 mol of combustion air are required.
Isothermal process
is a process in which the temperature maintained constant.
Perpetual-motion machine
is any device that violates either the first or second law of thermodynamics.
Law of Conservation of Energy
1st Law of Thermodynamics; states:
*energy cannot be created or destroyed
*energy can be transformed
Most relevant form of work in biochem is ___ work, because rxns occur at constant ___
pressure-volume ∆(PV)
thermal expansion
tendency of matter to change in volume in response to a change in temperature
third law of thermodynamics
the entropy of a pure crystalline solid at absolute zero is zero. this state corresponds to "perfect order" because all the atoms in this hypothetical state have no kinetic energy at 0 K
A mixture of gases is...
more disordered than a single gas
Saturation pressurePsat
is called the pressure at which a pure substance changes phase at a given temperature.
Ideal cycle
is an actual cycle stripped of all the internal irreversibilities and complexities. The ideal cycle resembles the actual cycle closely but is made up totally of internally reversible processes.
Gibb's free energy
the energy in a system that is available for work
2nd law of thermodynamics
for any spontaneous process in an isolated system, there is an increase in the value of entropy (S)
- as disorder increases --> entropy increases
-natural processes result in a net entropy gain of the system and surroundings
-heat does not flow from a cold body to a hot body

What is the hydrostatic balance?
Assuming a perfect balance between the upward pressure gradient force and the downward force of gravity. (∂p )/∂z≈-ρg
efficiency (eff)
ratio of the work we get out of a machine to the amount of energy put into a machine...[(work)out/(energy)in] x 100 = %
Work (Physics Definition)
The product of a force and a distance through which it acts
Mechanical efficiency
of a device or process is the ratio of the mechanical energy output to the mechanical energy input.
Pressure fraction
of a gas component in a gas mixture is the ratio of the component pressure to the mixture pressure. Note that for an ideal-gas mixture, the mole fraction, the pressure fraction, and the volume fraction of a component are identical.
Why do rxns occur spontaneously?
Because increase of entropy is driving the process forward
What is the pressure-work-volume equation and how is it found?
δW=p dV This found using the force formula and exchanging some variables to get what the work is equal to. Also the change in pressure in volume and area helped make up this equation too.
Dalton's law of additive pressures
states that the pressure of a gas mixture is equal to the sum of the pressures each gas would exert if it existed alone at the mixture temperature and volume.
What is the zeroth law of thermodynamics?
If object A is in temperature equilibrium with object B is in temperature equilibrium with object C, then object A and object C are in temperature equilibrium.
Isentropic efficiency of a turbine
is defined as the ratio of the actual work output of the turbine to the work output that would be achieved if the process between the inlet state and the exit pressure were isentropic.
gibbs free energy equation and constant parameters are what?
G =H -TS temperature and pressure are constant
Lower heating value LHV of fuel
is the amount of heat released when a specified amount of fuel (usually a unit of mass) at room temperature is completely burned, and the combustion products are cooled to the room temperature when the water formed during the combustion process leaves as a vapor.
Formula for finding Heat (q) absorbed by an object
q = (m) X (Cs) X (ΔT)
C(specific) is specific heat capacity
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