State the third law of thermodynamics and examples also the formula
Answers
Answer:
The third law of thermodynamics states that as the temperature approaches absolute zero in a system, the absolute entropy of the system approaches a constant value. This was true in the last example, where the system was the entire universe.
Explanation:
Hope this will help you.
Explanation:
however, do lead to massive changes in entropy as the possibilities for different molecular organizations, or microstates, of a substance suddenly and rapidly either increase or decrease with the temperature.
The Third Law of Thermodynamics
The third law of thermodynamics states that as the temperature approaches absolute zero in a system, the absolute entropy of the system approaches a constant value. This was true in the last example, where the system was the entire universe. It is also true for smaller closed systems – continuing to chill a block of ice to colder and colder temperatures will slow down its internal molecular motions more and more until they reach the least disordered state that is physically possible, which can be described using a constant value of entropy.
Most entropy calculations deal with entropy differences between systems or states of systems. The difference in this third law of thermodynamics is that it leads to well-defined values of entropy itself as values on the Kelvin scale.
Crystalline Substances
To become perfectly still, molecules must also be in their most stable, ordered crystalline arrangement, which is why absolute zero is also associated with perfect crystals. Such a lattice of atoms with only one microstate is not possible in reality, but these ideal conceptions underpin the third law of thermodynamics and its consequences.
A crystal that is not perfectly arranged would have some inherent disorder (entropy) in its structure. Because entropy can also be described as thermal energy, this means it would have some energy in the form of heat – so, decidedly not absolute zero.
Although perfect crystals do not exist in nature, an analysis of how entropy changes as a molecular organization approaches one reveals several conclusions:
The more complex a substance – say C12H22O11 vs. H2 – the more entropy it is bound to have, as the number of possible microstates increases with the complexity.
Substances with similar molecular structures have similar entropies.
Structures with smaller, less energetic atoms and more directional bonds, like hydrogen bonds, have less entropy as they have more rigid and ordered structures.
Consequences of the Third Law of Thermodynamics
While scientists have never been able to achieve absolute zero in laboratory settings, they get closer and closer all the time. This makes sense because the third law suggests a limit to the entropy value for different systems, which they approach as the temperature drops.
Most importantly, the third law describes an important truth of nature: Any substance at a temperature greater than absolute zero (thus, any known substance) must have a positive amount of entropy. Furthermore, because it defines absolute zero as a reference point, we are able to quantify the relative amount of energy of any substance at any temperature.
This is a key difference from other thermodynamic measurements, such as energy or enthalpy, for which there is no absolute reference point. Those values make sense only relative to other values.
Putting together the second and third laws of thermodynamics leads to the conclusion that eventually, as all energy in the universe changes into heat, it will reach a constant temperature. Called thermal equilibrium, this state of the universe is unchanging, but at a temperature higher than absolute zero.
The third law also supports implications of the first law of thermodynamics. This law states that the change in internal energy for a system is equal to the difference between the heat added to the system and the work done by the system:
\Delta U = Q-WΔU=Q−W
Where U is energy, Q is heat and W is work, all typically measured in joules, Btus or calories).
This formula shows that more heat in a system means it will have more energy. That in turn necessarily means more entropy. Think of a perfect crystal at absolute zero – adding heat introduces some molecular motion, and the structure is no longer perfectly ordered; it has some entropy.