Thermodynamics Flashcards
What is the zeroth law of thermodynamics?
when Object A is in thermal equilibrium with Object B, and Object B is in thermal equilibrium with Object C, then Object A and C are also in thermal equilibrium and no net heat flow happens
Temperature
proportional to the average kinetic energy of the particles that make up the substance
Heat
is the transfer of thermal energy from high temp/energy objects to low temp/energy objects (Unit = J)
Thermal Equilibrium
when there is no net heat flow between two objects and they are the same temp
Freezing and Boiling Points in Celsius
0, 100
Freezing and Boiling Points in Fahrenheit
32, 212
Freezing and Boiling Points in Kelvin
273, 373
Absolute Zero
theoretical temperature in which there is no thermal energy. K = 0, F = -460, C = -273
What is the third law of thermodynamics?
the entropy of a perfectly organized crystal at absolute zero is zero
How do you interconvert F and C?
F = 9/5C + 32
How do you interconvert C and K?
K = C + 273
Thermal Expansion
a change in the temperature of most solids results in a change in their length
What is the equation to measure linear thermal expansion?
deltaL = alpha*L*deltaT DeltaL = change in length alpha = coefficient of linear expansion L = original length deltaT = change in temperature
What is a coefficient of linear expansion?
constant that characterizes how a specific material’s length changes the temperature changes. Called alpha, Units = K^-1
What is the equation for volumetric thermal expansion?
deltaV = beta*V*deltaT DeltaV = change in volume Beta = coefficient of volumetric expansion DeltaT = change in temp
What is the coefficient of volumetric expansion?
exactly what it sounds like - constant that characterizes how a specific material’s volume changes as the temperature changes. Called beta, Units = K^-1
What is the relationship between the linear expansion and volumetric expansion coefficients?
beta = 3alpha
Isolated Systems
not capable of exchanging energy or matter with their surroundings so total change in internal energy must be zero; rare in reality
Closed Systems
capable of exchanging energy but not matter with their surroundings
Open Systems
can exchange both matter and energy with the surroundings
State Functions
thermodynamic properties that are a function of only the current equilibrium state of a system. They are independent of that path they take to get to a particular equilibrium state
Ex: pressure, density, temp, volume, enthalpy, internal energy, Gibbs free energy, and entropy
Process Functions
describe the path taken to get from one state to another
Ex: work, heat
First Law of Thermodynamics
states that the change in the total internal energy of a system is equal to the amount of energy transferred in the form of heat to the system, minus the amount of energy transferred form the system in the form of work.
Equation for change in internal energy
deltaU = Q - W deltaU = change in system's internal energy Q = energy transferred into the system as heat W = work done by the system
Second Law of Thermodynamics
objects in thermal contact and not in thermal equilibrium will exchange heat energy such that the object with the higher temperature will give off heat energy to the object with the lower temperature until both objects have the same temperature at thermal equilibrium
1 Cal = ? J
4184 J
Conduction
the direct transfer of energy from molecule to molecule through molecular collisions. Must have direct contact, metals are best at this
Convection
the transfer of heat by a physical motion of a fluid over a material; only liquid and gases can transfer heat. This is a common use in convection ovens
Radiation
the transfer of energy by electromagnetic waves; only way to transfer energy in a vacuum
Specific Heat
Specific heat (c) of a substance is defined as the amount of heat energy required to raise one gram of a substance by one degree C or one unit K.
What is the specific heat of water in calories?
1 cal/ g*K
What is the equation that relates heat gained or lost by an object and the change in temp of that object?
q = mcdeltaT q = amount of heat gained or lost from the material m = mass c = specific heat of the substance deltaT = change in temp (C or K)
What is the equation for calculating the amount of heat added or removed for phase changes?
q = mL q = amount of heat gained or lost from the material m = mass L = heat of transformation(fusion or vaporization)/latent heat - will be provided
Solid to Liquid is
fusion/melting
Liquid to Solid is
freezing/solidification
Liquid to Gas is
boiling/evaporation/vaporization
Gas to Liquid is
condensation
Solid to Gas is
sublimation
Gas to Solid is
deposition
What is the heat of transfer called when it occurs at a melting point?
heat of fusion
What is the heat of transfer called when it occurs at a boiling point?
heat of vaporization
What is a process with constant temp called and its equation?
isothermal (deltaU = 0)
Q = W
What is a process with no heat exchange called and its equation?
adiabatic (Q = 0)
deltaU = - W
What is a process with constant volume called and its equation?
isovolumetric/isochoric (W = 0)
deltaU = Q
Entropy
measure of the spontaneous dispersal of energy at a specific temperature: how much energy is spread out or how widely spread out energy becomes in a process
Energy Into System = Increases Entropy
Energy Out System = Decreases Entropy
Equation for entropy
deltaS = Q(subrev)/T deltaS = change in entropy Q(subrev) = heat that is gained or lost in a reversible process T = temp in K Units = J/mol*K
