## Welcome to Cosmology and Thermodynamics       ## Learning Thermodynamics - an Experimental Science.

Studying Thermodynamics is more that just manipulating many formulae, of which these are just a few,

Q  =  ∆U  +  W  (Which expresses the First Law of Thermodynamics).

∆G  =  ∆H  -  T∆S   (An important equation for Gibb’s Free Energy).

(∂S/∂T)P  =  CP /T   (An equation for the change in entropy).

d(loge KP )/dT  =  ∆H/RT2  (An equation for equilibrium constant).

I want to encourage my readers actually to do some experiments.  You could start by measuring the Joule-Thomson Effect of air.  This could be done by measuring the pressure of air in the spare tyre of a car and then letting down the pressure and measuring the temperature of the released air.  You will find that the temperature of air falls by about 1oC, - but don’t take my word for it!  In any case, the result depends on the initial high pressure in the tyre, so you will need to do a range of experiments.

Then, if you have the facilities, try the same experiment with hydrogen, - letting down the pressure from (say) 100 atmospheres to one atmosphere.  The temperature does not fall, but rises slightly.  This is the Joule-Thomson Warming Effect.  The free expansion of hydrogen (above 200 K) leads to an increase in temperature not a fall in temperature.  Note that this is contrary to what cosmologists say about the expanding Universe.

Practical Thermodynamics involves the properties of matter :-

Pressure,  temperature,  density,  specific heat capacity,  enthalpy,  internal energy,  entropy,  latent heat,  ionization energy and other properties.  Understanding the significance of these properties involves more than merely studying mathematical equations.

In learning about Thermodynamics I urge you to get your hands dirty by studying machinery.

What about going to an electric power station and studying the steam turbines which drive the generators?  Take measurements of the steam entering the turbine

pressure,

temperature,

flowrate.

Then apply this data to a Temperature-Entropy Diagram for steam (or use steam tables) in order to evaluate the enthalpy and entropy of the steam.  Also measure the pressure and temperature of the steam leaving the turbine and again - evaluate the enthalpy and entropy of the exit steam.  Plot the path of the expanding steam on the Temperature-Entropy Diagram.  Use this thermodynamic data to calculate the enthalpy change of the steam. Does this enthalpy change balance the electric power generated?

How does the entropy change?  Is the expansion of the steam isentropic?

How does this data match up with the First and Second Laws of Thermodynamics?

It is only by having real practice at Thermodynamics that a person can gain a grasp of the subject, in the same way that one can only learn to play the violin by practice;  a mere theoretical knowledge of vibrating strings is not enough.

A more ambitious programme is to estimate the energy of activation of a chemical reaction by doing a number of experiments over a range of temperatures and then applying the Arrhenius equation,

loge k  =  - E/RT  +  constant

For more examples of the practical application of Thermodynamics with numerical data, see my book,    "The Big Bang Exploded!   Cosmology Corrected,   A Commentary with Thermodynamics".

The thermodynamic properties of hydrogen are encapsulated in a Temperature-Entropy Diagram which is a valuable tool.   