from calories to space
The desire to understand the mysteries that govern the functioning of the Universe is one of the traits that best characterizes us. And of course, as part of this search, understand energy behavior is the key point. In this context, thermodynamics is one of the most important applications of physics because it allows us to understand how energy flows and transforms in different systems, from the most microscopic to the macroscopic.
For many years, everything we knew about this discipline was structured around four fundamental principles which, in addition to providing a very solid theoretical basis, are capable of explaining phenomena as diverse as the expansion of gases, the efficiency of heat engines, the evolution of stars, and even the biological processes occurring inside our cells. We tell you clearly what they are.
ZERO PRINCIPLE: HEAT BALANCE AND TEMPERATURE
Thermodynamics is based on the zero principle, which establishes rules for understanding temperature on my own and thermal equilibrium between different physical systems. To understand this, you have to imagine two objects, each at a different temperature, coming into contact. Well, the zero principle states that after a certain time, both objects will fall apart. reach the same temperature and bring yourself into “thermal equilibrium”, thereby stopping the heat exchange between them.
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This principle, obvious to anyone, is important for laying the foundations that define the concept of temperature. Thus, it is defined as a system associated with speed with which particles move and collide with each other: particles moving at higher speeds and interacting with each other more aggressively will increase the temperature of the system, while as collisions ebb and flow, the temperature will fall.
FIRST PRINCIPLE: ENERGY SAVING
The first principle is the one that takes as its basis energy saving, stating that the total energy of an isolated system always remains constant. Doesn’t this seem familiar to you? Well yes, this is a famous statement that says that energy cannot be created or destroyedbut only transforms from one form to another: energy can change from one form to another, but the total amount is always constant.
In light bulbs, electrical energy is converted into light and heat, but never disappears.
This principle has important implications ranging from the combustion of fuel inside an engine to the functioning of cells. In the most everyday situations we can observe the First Principle when we turn on bulb: Electrical energy is converted into light and heat, but the total amount of energy always remains constant.
SECOND PRINCIPLE: GROWTH OF ENTROPY
The second principle is the one that introduces the concept entropywhich, in simple terms, is the degree mess, chaos or energy dissipation within a system. This principle states that in a closed system, entropy always tends to increase with time. This concept is also commonly associated with irreversibility of processes, that is, with the fact that the action can be performed without changes in reverse. For example, when breaking an egg, it is easy to see that it will not unfold spontaneously, so entropy increases.
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In everyday life, we can imagine a cup of hot coffee placed in a room with a low temperature. Initially the heat is concentrated in the cup, but over time the heat will eventually dissipate around the room, trying to find that thermal balance that he talked about in “The Zero Principle.” Thus, this is an example of how entropy increases due to the expansion and chaotic distribution of thermal energy.
The heat from a hot cup of coffee in a cold room dissipates over time, increasing entropy.
THIRD PRINCIPLE: ABSOLUTE ZERO
The third principle brings with it a very important term in physics: Absolute zero. This state, although practically unattainable for any object or system, can be any in which the particles are completely stationary, do not experience any vibration or movement, and are identified as 0 degrees Kelvin or -273 degrees Celsius. Thus, this principle postulates that as the temperature of a system approaches the value of absolute zero, the entropy of the system will tend to a minimum and constant value.
This principle is usually illustrated the impossibility of the system reaching this absolute zero on practice. And as we approach this limiting temperature, it will take an infinite amount of energy to continue extracting heat from the system, which would be completely impossible. The third principle also applies to the relationship between temperature and molecular disorder: As we approach absolute zero, entropy decreases and cellular structures acquire a much more ordered structure due to limited vibration and minimal movement of the particles that form it.