Definitions Flashcards
Open System
A system which can exchange both energy and matter with its surrounding.
Closed System
A system which can exchange energy but not matter across its boundary.
Isolated System
A system which can exchange neither energy nor mass with its surrounding.
Surrounding
The part of the Universe that isn’t the system, which can interact with the system.
Boundary
Anything which separates the system from the surrounding.
Intensive properties
Properties of the system that do not depend on the mass of the system. (T, P, C)
Extensive properties
Properties of the system that depend on the mass of the system. (V, E, H, S)
State variables
The variables which are required to be defined in order to define the state of any system. (P, V, T, U, H, S)
State functions
Properties of a system which depend only on the state of the system and not on the path. (U, S, H, A)
Process
The path along which a state of a function changes.
Isothermal process
A process which takes place at constant T.
Isobaric process
A process which takes place at constant P.
Isochoric process
A process which takes place at constant V.
Adiabetic process
A process during which transfer of heat cannot take place between the system and surrounding.
Cyclic process
A process in which the system comes back to its initial state after undergoing a series of changes.
Reversible process
A process during which the system always departs infinitesimally from the state of equilibrium.
(It’s direction can be reversed at any moment)
Irreversible process
A process during which the system and the surroundings do not return to their original condition once the process is initiated.
Zeroth law of thermodynamics
If two thermodynamic systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other.
First law of thermodynamics
🔼U = Q + W 🔼U = change in internal E of the system Q = heat absorbed by the system W = work done on the system
Second law of thermodynamics
The state of entropy of the entire universe, as an isolated system, will always increase over time.
Enthalpy
H = U + PV H = enthalpy U = internal energy P = pressure V = volume
Gibbs free energy
🔼G = 🔼H - T🔼S 🔼G = change in Gibbs free energy 🔼H = change in enthalpy 🔼T = temperature in K 🔼S = change in entropy (the maximum reversible work that is obtained from a particular system) Constants --> T, P
Helmholtz energy
A = U - TS A = Helmholtz free energy U = internal energy T = temperature in K S = entropy (the useful work that is obtained from a particular system) Constants --> T, V
Path functions
Properties of a system whose values depend on the transition of the system from the initial state to the final state. (Q, W)
Cp
(specific heat at constant pressure)
The amount of energy needed to raise the temperature by 1K at constant P.
Cv
(specific heat at constant volume)
The amount of energy needed to raise the temperature by 1K at constant V.
