The zeroth law of thermodynamicsWatch
I know that's a ton to ask but I'm not sure how a law that essentially says that if two objects are in contact with another object and are at the same temperature as the object then all objects will be in thermal equilibrium can do all of those things 🙂
Imagine you have a volume of water kept at a constant 50 degrees Celsius, we can reference this as object A. Now we introduce a thermometer, which consists of a glass wall (object B) housing another volume of liquid (object C).
As the zeroth law of thermodynamics states, if object A is in thermal equilibrium with object B (the water and glass), and object B is in thermal eqm. with object C (the liquid), then object A and object B should also be in thermal eqm.
Given we know certain properties about the liquid within the thermometer (relating to its thermal expansion), do you see how when thermal equilibrium is reached, and we have some relative indication of the difference in this 'quantity', how the zeroth law played a crucial part?