Thermodynamics Flashcards
What is thermodynamics?
Thermo means heat and dynamics means motion
What is
1. System
2. Surrounding
3.Boundary
- A system usually have a definite body
- remaining universe excluding the system
- region separating the system from the surroundings
what is
1. isolated system
2. open system
3. closed system
- system that cannot exchange matter and energy w the surroundings
- system that can exchange energy and matter w the surroundings
- system that can exchange energy but not matter w the surroundings
difference bw homogeneous and heterogeneous system
homogeneous - uniform throughout
heterogeneous - non uniform system
Intensive vs extensive properties
Intensive properties - properties that do not depend upon amount of substance present and only depends on nature (temp., density etc.)
Extensive properties - properties that depend upon amount of substance present (enthalpy, mass etc.)
What is constant in:
1. Isothermal
2. Adiabatic
3. isobaric
4. isochoric
5. cyclic
- temp constant
- no heat change
- pressure constant
- volume constant
- initial and final state of system is same
what is internal energy?
total amt of energy associated w given substance
△E = Ef - Ei
what is enthalpy?
- heat content of a system
sum of internal energy and pressure - volume change
H= E + pv KJmol(inv)
Enthalpy change
△H = Hf - Hi
△H = △E + p△v
what is Zeroth law of thermodynamics?
when two bodies of variable temp are brought together in contact, then attain same temp after some time and gain thermal equilibrium.
what is first law of thermodynamics?
energy can neither be created not destroyed it can only be converted from one form to another
E2 = E1 + q - w (w = p△v)
△E = q - p△v
change in int. energy = heat supplied to the system - work done by the system
why we need second law of thermodynamics?
- predicts feasibility of process
- predict direction of energy
- direction of spontaneous process
what is second law of thermodynamics?
work can always be converted into heat but heat can never be entirely convert to work only some portion of heat converts to work rest remains unconverted.
what is entropy?
randomness in molecular system
△S = △q/ T
△S total = △S system + △ S surrounding
what is spontaneous process?
process that proceeds on its own without any outer assistance. takes place only when △S total is positive
△G = - T△S
