Topic 8 Thermodynamics and Chemistry
By this time, Lavoisier’s hunt for the “heat particle” caloric was in vain.
It was also due to the age of industrialization that there was a considerable amount of interest in heat, work, and maximizing efficiencies in engines.
Yet, by the early 1800s, there was still no clear theory on how these steam engines work.
8.1 Beginnings of Thermodynamics
8.1.1 Sadi Carnot
Figure 8.1: An Artist’s Rendition of Carnot
Carnot (1796 - 1832) was a scientist who tried to understand how heat worked. He thought that heat was some form of “caloric fluid” that flowed from hot to cold, doing work in the process.
Figure 8.2: Carnot Cycle in Thermodynamics
Carnot’s work eventually lead him to the development of the Carnot cycle - a concept that paved the way for the second law of Thermodynamics (i.e., entropy is always increasing in the universe).
Unfortunately, Carnot succumbed to cholera when he was 36.
8.1.2 Conservation of Energy
Figure 8.3: A Photograph of Joules
James Prescott Joule (1818 - 1889) was an English student of Dalton who attempted to quantify the amount of energy that came from mechanical work.
Figure 8.4: A Sketch of Mayer
At around the same time, another Physician and Scientist by the name of Julius Robert von Mayer (1814 - 1878) also came up with similar conclusions about energy from mechanical work that Joule did.
8.1.3 Hess’ law and entropy
Figure 8.5: Hess’ Law Applied to a Chemical Reaction
In 1840, Robert Hess (1802 - 1850) came up with Hess’ Law.
If a chemical reaction occurred via different routes, then the overall energy change should be the same regardless of the routes taken.
8.1.3.1 Origins of entropy
Based on his preceding work On the Moving Force of Heat and the Laws of Heat which may be Deduced There from published in 1850, Rudolf Clausius (1822 - 1888) laid down the first two laws of thermodynamics in his own words:
“In a physical system without energy exchanges with the external world, the total energy is conserved.”
– First law of Thermodynamics
“Heat cannot flow from a cold to a warm body without the expense of energy.”
– Second law of thermodynamics
In 1865, Clausius then introduced the idea of entropy.
8.1.4 Formation of the Kelvin temperature scale and the term “thermodynamics”
Figure 8.6: An Artist’s Impression of Lord Kelvin
William Thomson (i.e., Lord Kelvin) (1824 - 1907) defined an absolute temperature scale that was based on the Carnot cycle.
He proposed that absolute zero or zero Kelvins equaled -273.16 Celsius. Hence, this is how the Kelvin temperature scale came into existence!
Lord Kelvin also introduced the term “Thermodynamics”.