Final answer:
The critical temperature (Tc) is the highest temperature at which a substance can exist as a liquid. When Tc is very low, it enables high thermodynamic efficiency as less heat is needed to generate work. The critical point is defined by Tc and critical pressure (Pc), which is not related to basin dimensions.
Step-by-step explanation:
Definition of Critical Temperature (Tc)
The critical temperature (Tc) is defined as the highest temperature at which a substance can exist in the liquid state. When Tc approaches 0 Kelvin, the maximum efficiency of a thermodynamic cycle can approach 100%. This is because at very low temperatures, only a small amount of heat (∆Q) is required to cause a significant increase in entropy (∆S), allowing nearly all the energy to be converted into work (∆W).
In the context of thermodynamics and phase diagrams, the critical point of a substance is marked by the critical temperature and the accompanying critical pressure (Pc), where the substance can neither be distinguished as a liquid nor a gas. The critical point is significant because beyond this point, the substance exists as a supercritical fluid with unique properties. The basin's dimensions are not directly related to the definition of Tc since Tc is an intrinsic property of the material. However, in practical applications, such as in heat engines, the environment's ability to provide a sufficiently cold bath places a practical limit on achieving temperatures near 0 Kelvin and thus extremely high efficiency.