THE LAWS OF THERMODYNAMICS
We’ve learned about two ways in which energy can be transferred between a
system and its environment. One is work, which takes place when a force acts over
a distance. The other is heat, which takes place when energy is transferred due to a
difference in temperature. The study of the energy transfers involving work and
heat, and the resulting changes in internal energy, temperature, volume, and pressure
is called thermodynamics.
The Zeroth Law of Thermodynamics
When two objects are brought into contact, heat will flow from the warmer object
to the cooler one until they reach thermal equilibrium. This property of temperature
is expressed by the zeroth law of thermodynamics.
If objects 1 and 2 are each in thermal equilibrium with object 3, then
objects 1 and 2 are in thermal equilibrium with each other.The First Law of Thermodynamics
Simply put, the first law of thermodynamics is a statement of the conservation of
energy that includes heat.
Energy (in the form of heat) is neither created nor destroyed in any
thermodynamic system.The mathematical equation that corresponds to this law is
ΔU = Q − WWhere ΔU is the change in internal energy of the system, Q is the heat added to the
system, and W is the work done by the system. U depends on the state of the system.
Consider the following example. An insulated container filled with an ideal gas
rests on a heat reservoir (something that can act as a heat source or a heat sink).
The container is fitted with a snug, but frictionless, weighted piston that can be