The Laws of Thermodynamics

The First Law of Thermodynamics  ?U = Q- W            

       Thermodynamics also involves the study of the change in thermal properties of matter . The First Law of Thermodynamics is merely a restatement of the law of conservation of energy , which states the energy is neither created nor destroyed , but can be changed into other forms.    

         Another example of changing the amount of thermal energy in a system is a hand pump used to flate bicycle tire.As person pumps , the air and the hand pump become warm.The mechanical energy in the moving piston is conservated into thermal energy of the gas.                                 

   Joule carried out experiments in the years ( 1843-1849) which demonstrate the equivalence of heat energy and the energy of work.

           1Cal = 4.1840 x10⁷  erg = 4.1840 Joules.

The First Law was mathematically formulated by Clausius :

?Q= dE + pdv             

The Second Law of Thermodynamics

     Rudolf Clausius (1822-1888) in 1850 : Heat can never pass on its own from a cooler reservoir to a warmer one .

    William Thomson ( Lord Kelvin , 1824-1907) in 1851 :

The impossibility of a perpetured motion machine of the second kind.

The Zeroth Law of Thermodynamics

When two systems are in thermal equilibrium with a third system , then they are in equilibrium with one another.

The Third Law of Thermodynamics

    The third Law (also called Nernst ^,s theorem ) makes statements a bout the temperature dependence of thermodynamics quantituis in the limit T? 0 .

Temperature:  may be measured in the Celsius, on which freezing point of water is 0 ⁰C , and the boiling point (under standered condition)is at 100 ⁰C .

Kelvin ( or absolute) scale is displaced 273 .15 ⁰C.

                   Fahrenheit temperature = 9/5 (Celsius temperature)+ 32.