What is Entropy? One of the Most Fascinating Concepts in Physics!
Entropy is a crucial concept for both physics and chemistry. It is the concept that explains, for example, why ice melts as it does. But understanding what exactly entropy is is not an easy task. This great TED-Ed video tells us in five minutes.
Basically entropy is a magnitude of thermodynamics like temperature, density, mass or volume. It is represented by the letter "S" and serves to explain why some physical processes happen in a certain way by measuring the degree of disorder of a system at the molecular level.
The problem with this definition is that the degree of disorder to which it refers is not very intuitive. As explained in TED-Ed, a glass of water is much more messy than one with a pile of ice cubes, although at first glance it may not seem so. In the video they recommend to think the entropy from the point of view of the probability.
In any thermodynamic system in equilibrium different energy microstates coexist at a molecular level compatible with the general state of the system. Entropy, in essence, is a measure that calculates the probability of changes occurring in the system as a function of the probability of its microstates.
Applied to a dynamic system, entropy is the measure that explains why, if we put a hot object next to a cold one, the cold gets hot and the hot one cools. There is a possibility that it happens backwards (that the hot object gets hotter and the cold gets colder still), but it is so small that it simply never happens because the energy tends to expand.
Additionally, the concept of entropy is also used to measure the probability of receiving a set of messages in an information environment.
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