First Law of Thermodynamics

Internal energy

Of a sustenance is the sum of the random distribution of microscopic kinetic and potential energies of the molecules of the system

*determined by th state of the system

Ke - temp

Pe - mass/vol/no of mol

Internal energy of an ideal gas

intermolecular force of attraction between molecules in an ideal gas is negligible, microscopic pe assumed to be 0 of the internal energy is the sum of microscopic ke only

U (ideal gas) = KE (microscopic)

= 3/2 Nkt = 3/2 Nrt = 3/2 pV (only depends on temp for U of ideal gas)

2 things heating can do

1. Increase temp

   • Increase speed, Increase microscopic ke, increase U

2. Change in phase

   • Increase separation, Increase microscopic pe, increase U

   • Te (latent heat) used to overcome attractive forces between atoms and break lattice struc/break bonds and hence temp remains constant (p2 phases coexist until transition is complete)

Specific heat capactiy

Of a substance defined as the thermal energy per unit mass required to raise the temperature of the substance by one degree

Specific latent heat of fusion

Of a substance is defined as the thermal energy per unit mass to change the phase of the substance from solid to liquid without any change in temperature

Specific latent heat of vap

Of a substance is the is defined as the thermal energy per unit mass required to change the phase of the substance from liquid to gas, without any change in temperature

First law of thermodyanamics

States that the increase in internal energy ◇U is equal to the sum of the heat supplied to system Q and the work done on the system W in a closed system

Insulated

No heat can enter or leave