LAWS OF THERMODYNAMICS

SYSTEM & SURROUNDINGS

System refers to the part of universe chosen for our study

The portion of universe excluded from the system is called surroundings

Types of systems

open system

A system which can exchange both matter and energy  with its surroundings is called open system.

Eg: hot coffee kept in a open vessel

Closed system

A system which can exchange  energy but not matter is  with its surroundings is called open system.

Eg: hot coffee kept in a closed vessel with conducting walls

Isolated system

 A system which can neither exchange  matter or energy  with its surroundings is called open system.

Eg:hot coffee kept in a thermos flask

  STATE FUNCTION & PATH FUNCTION

Property of a system depends only on the state of system and not depend on the path along which that state is attained is called state function

Eg:Pressure , volume , temperature

Property of a system which depends on the path along with the state is attained

is called path function

Eg: work, heat

INTENSIVE & EXTENSIVE PROPERTIES

Properties which are independent of amount of matter present in a system is called intensive properties

Eg:Pressure , viscosity , temperature

Properties which are dependent of amount of matter present in a system is called intensive properties

Eg: Mass, Volume , Energy

ENERGY OF A SYSTEM

Energy of a system is its capacity to do work. When a system does work, its energy is reduced and when work is done on a system its energy increases.

ADIABATIC & ISOTHERMAL PROCESS

A process in which no heat enters or leaves the system is called an adiabatic process. In such process the system is completely insulated from the surroundings.

An isothermal process is one which the temperature of the system remains constant throughout.In such a system energy can exchange to surroundings

ENDOTHERMIC & EXOTHERMIC PROCESS

process which liberates energy as heat is called an exothermic process

process which liberates energy as heat is called an exothermic process

REVERSIBLE PROCESS & IRREVERSIBLE PROCESS

A reversible process is one which is conducted infinitesimally slowly such that at every stage the driving force is only infinitesimally greater than the opposing force.. Such a process can be reversed by increasing the opposing force by an infinitesimal amount.
A process in which the driving force at any stage is greater than the opposing force is called an irreversible process.
All natural forces are irreversible.
INTERNAL ENERGY OF A SYSTEM(E)
The internal energy is the sum of total energies associated with the translational,rotational, vibrational,electronic, and nuclear motions at the molecular level as well as potential energy of interaction between constituent particles.

ENTHALPY(H)

Enthalpy is the sum of internal energy and pressure volume energy.
H=E+PV

THE ZEROTH LAW

Two systems that are both in thermal equilibrium with a third system are in thermal equilibrium with each other

FIRST LAW OF THERMODYNAMICS

Energy can neither be created nor destroyed it  may be converted from one form to another

SPONTANEOUS PROCESS

A  process which has a natural urge to take place by itself under a given set of conditions.

ENTROPY

Entropy is a measure of disorder or randomness in a system.

Greater the entropy greater the disorder

SECOND LAW OF THERMODYNAMICS

The entropy of the universe remains constant in a reversible process where as it increases in a irreversible process

GIBBS FREE ENERGY

It is the maximum amount of energy available with a system that can be converted into useful work or free energy the measure of the capacity of a system to do useful work
G=H-TS(Gibbs -Helmholtz equation)
A process should be spontaneous only if the free energy change is negative.

 JOULE THOMSON EFFECT

When a gas under high pressure is allowed to explain under adiabatic conditions through a porous plus in to a region of low pressure, there occur  a change in its temperature. When a gas expands adiabatically some work is done by the gas to overcome the van der waals  force of attraction between molecules.This is done at the cost of the kinetic energy of the gaseous  molecules.Then the internal energy decreses the temperature decreases