Zeroth Law of Thermodynamics
Definition and meaning of Zeroth Law of Thermodynamics in chemistry.
The zeroth law of thermodynamics states that if two thermodynamic systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other. This fundamental principle establishes temperature as a measurable and consistent property of matter.
In more detail
Thermal equilibrium means that no net heat flows between systems when they are connected by a path permeable to heat. Even though it is the most basic law of thermodynamics, it was formulated after the first and second laws were already established, hence the name 'zeroth' law to ensure it precedes the others logically. It ultimately justifies the practical use of thermometers, as the thermometer acts as the third system that comes into equilibrium with the object being measured.
Key facts
| Field | Physical Chemistry |
|---|---|
| Core concept | Thermal equilibrium |
| Implication | Defines the concept of temperature |
If a cup of coffee and a glass of ice water are left in a room until they both reach the room's temperature, they will not exchange heat if placed in contact with each other.
Frequently asked questions
Why is it called the zeroth law?
It was formalized after the first three laws were already widely accepted, but its foundational nature required it to be placed before them numerically.