tell me about Important points of chapter Thermodynamics...Formula
Answers
Thermodynamics:- It is the branch of physics which deals with process involving heat, work and internal energy. Thermodynamics is concerned with macroscopic behavior rather than microscopic behavior of the system.
Basic Terminology:-
System
Part of the universe under investigation.
Open System
A system which can exchange both energy and matter with its surroundings.
Closed System
A system which permits passage of energy but not mass, across its boundary.
Isolated system
A system which can neither exchange energy nor matter with its surrounding.
Surroundings
Part of the universe other than system, which can interact with it.
Boundary
Anything which separates system from surrounding.
State variables
The variables which are required to be defined in order to define state of any system i.e. pressure, volume, mass, temperature, surface area, etc.
State Functions
Property of system which depend only on the state of the system and not on the path.
Example: Pressure, volume, temperature, internal energy, enthalpy, entropy etc.
Intensive properties
Properties of a system which do not depend on mass of the system i.e. Temperature, pressure, density, concentration,
Extensive properties
Properties of a system which depend on mass of the system i.e. Volume, energy, enthalpy, entropy etc.
Process
Path along which state of a system changes.
Isothermal process
Process which takes place at constant temperature
Isobaric process
Process which takes place at constant pressure
Isochoric process
Process which takes place at constant volume.
Adiabatic process
Process during which transfer of heat cannot take place between system and surrounding.
Cyclic process
Process in which system comes back to its initial state after undergoing series of changes.
Reversible process
Process during which the system always departs infinitesimally from the state of equilibrium i.e. its direction can be reversed at any moment.
Kinetic Energy:- Energy possessed by the atoms or molecules by virtue of their motion is called kinetic energy.
Internal Energy (ΔU):- Sum total of kinetic and potential energies of atoms/molecules constituting a system is called the internal energy of the system.
(a) ΔU is taken as positive if the internal energy of the system increases.
(b) ΔU is taken as negative if the internal energy of the system decreases.
Heat:- Heat is the part of internal energy which is transferred from one body to another an account of the temperature difference.
Work:- Work is said to be done when a force acting on a system displaces the body in its own direction.
dW = Fdx = PdV
W = P(Vf -Vi)
(a) If the gas expands, work is said to be done by the system. In this case Vf > Vi, therefore, W will be positive.
(b) If the gas is compressed, work is said to be done on the system. In this case Vf < Vi, therefore, work done is negative.