| Law zero, formulated in 1931: As the time is the basic variable in the Dynamics so the temperature is the fundamental variable in Thermodynamics. The zero law of thermodynamics introduces the concept of "temperature". Knowing the temperature we can establish if among two "bodies" will be possible an heat exchange. Among two bodies at the same temperature isn't possible exchange heat. |
| First Law: Energy keeps. The fact that energy, and not heat, keeps was known since the middle of the XIX° century and is the conclusion of the Kelvin and Clausius works. The energy dethroned the Newtonian concept of "force". |
| Second law: The second law acknowledges that in nature exists a fundamental asymmetry: a warm object cools, but a cool object couldn't, spontaneously, to warm up. This concept says that notwithstanding energy keeps, her distribution changes in a irreversible way. |
| Third law: The third law says that isn't possible to reach the absolute zero in the absolute temperature scale. The volume of a gas decrease (or increase) of 1/273 of his initial value for any drop (or rise) of 1°C in temperature. Cooling a gas to -273°C could mean to vanish his volume and his pressure. This critic point (impossible to reach) is called Absolute Zero and the temperatures measured out from this point are called "Absolutes Temperatures". The boiling water has a temperature of 100°C in the Celsius scale and a temperature of 373° in the absolute scale. Pratically none gas can't reach the absolute zero and vanish his volume. Before to reach the absolute zero any gas condenses changing in a liquid (that can't have a volume equal to zero). The absolute scale of temperature is named Kelvin scale. |