The Third Law of Thermodynamics

The Third Law of Thermodynamics

   Desember 05, 2017       Unknown

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Fikri Haikal | 16630021

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            The third law of thermodynamics defines what absolute zero is, and ties together the concept of entropy and temperature. Many research for finding or approaching the absolute zero is using the concept of entropy itself. The coldest place known in the universe is the universe is the boomerang nebula with temperature freezing to -272K or 1K above absolute zero. Although researcher would never get the absolute the absolute zero experimentally, they’ve approach absolute zero closer than the nature itself, with surprisingly 500nK of Sodium and Potassium molecule by using specified laser. The reason why we could not able to reach absolute zero is the second law of thermodynamics itself. It states that heat will be spontaneously move from hotter object into the colder object.

            The third law in its earliest form was prostulated by Nernst in 1906, or known to be Nernst Heat Theorem. Later, his theorem has been clarified and refined by other scientist, such as Simon. Until the law that we know today, which its stated that :

            “The entropy of perfect crystal at the absolute zero temperature is minimum or zero”

The third law itself was a controversy once. There were many quotation from scientific paper about it. Some of them who quotioned about the law divined by two, those who held that the law was true but inapplicable and those who maintained that though applicable it was false. Now, the third law is more fully understood and no longer controversial.

Figure 1 Example of Crystal Defects, which can be energy carrier and never able get minimum entropy

            Perfect crystal is stated because we can only reach minimum entropy by a perfect crystal. A perfect crystal is a crystal where there are no defects in it and it is built by perfectly arranged identical atom in perfectly symmetry ways. Because defect can carry energy, and wont be minimize the entropy itself. So we can only reach zero entropy with perfect crystal. 

            Mathematically, we can express the third law by the equation:

                        S          =          k ln N

Where for the perfect crystal, the N is only one, hence

                        S          =          0

            The example of third law of thermodynamics, is when we try to minimize both the temperature and entropy of CO gases by solidify it through pressure release and causes temperature drop. And successfully drop its entropy by turning the gas into solid form.  

Figure 2 Temperature drop of CO₂ as it solidified

         

Although the third law of thermodynamics seems obvious, simple and theoretical. It cannot be ignored to complete the pieces of thermodynamics law. And can be used for further research in the future.

References:

The Royal Institution. “What is the Third law of Thermodynamics?”. (https://www.youtube.com/watch?v=kswiDQ2aAKA) accessed: 1 December 2017.