Chemical Energy is a form of potential energy, but deserves its own mention as to its importance. It is the result of chemical energy that we consume food for our bodies to process, that plants absorb photonic radiation for photosynthesis, and why material burns. In the case of wood, when you produce large amounts of kinetic energy you excite the molecules enough to compel them to interact with other atoms and molecules. With enough kinetic energy, and the introduction of oxygen from the air around it, wood will undergo a chemical reaction called "combustion," and break down its cellulose molecules; which are made up of carbon, hydrogen, and oxygen into CO2 and H2O while also release kinetic energy in the form of heat.
Kinetic Energy deals with the energy produced as the result of motion. The flow of atoms and molecules requires energy to move, and if you are familiar with Newton's Laws of Motion, then you know this to be evident.
- Newton’s First Law: Every object persists in its state of rest or uniform motion in a straight line unless it is compelled to change that state by forces impressed on it.
- Newton's Second Law: Force is equal to the change in momentum (mV) per change in time. For a constant mass, force equals mass times acceleration. F = m*a
- Newton’s Third Law: For every action, there is an equal and opposite reaction.
All that is required is an external force to be applied. This can come from a fundamental force, like gravity, or from another system from which work is used as the external force. Any engine can be the source, but even those engines have their own energy sources.
- A hot air balloon will use a heat engine to produce less dense hot air that will fill the balloon to provide upward lift to the basket, but the engine that generates that heat will use chemical energy through combustion to generate the energy to do so.
- A manual engine, like a crank or a plow, can use the force of a human or other animal, but the work that we all generate comes from the energy we derive from food.
- Wind and hydroelectric turbines generate chemical energy from the flow of air and water respectively, but those flows are the result of their systems. In the first case, the wind caused by atmospheric differences coming from hot and cold air; is a type of heat system. In the second case, the flow of water down rivers; is a type of gravity system.
Internal Energy/Thermal Energy is merely the sum of both potential energy and kinetic energy. But reaching back to fundamentals, what is actually occurring? The answer is the movement of atoms and molecules in relation to other atoms and molecules, based on the laws of the fundamental electromagnetic force. When they translate, rotate, or vibrate, they produce energy. The repulsive force of electromagnetism bump and jostle others around. It is from the cumulative effects of the internal energy of these systems that we can dissipate or harness that energy through heat or work.
Heat is the sum of all thermal energy that is transferred to and from the system. Heat going into a system may be like the energy from a stovetop or fire being radiated and conducted into a pot of water. The thermal energy of the container is increased and is subsequently conducted into the water itself, and in turn, will result in the water in the pot boiling into a gas. The thermally energetic steam ends up carrying that energy into the surrounding air. So energy is generated from a heat source, like from the chemical energy from fire, is imparted into the pot and water, while heat leaves the system in the form of either steam or just dissipated straight into the air from the heat source itself.
Temperature is merely the average kinetic energy of the system whereas that thermal/internal energy was the sum. This average is in relation to a system. Hence the reason why a pot of boiling water will have a temperature of 212 Fahrenheit, but the temperature of the universe is -455 Fahrenheit. The pot is treated as its own system, just as the entirety of the universe is, but the average kinetic energy of the universe include the kinetic energy of that pot. The temperature of the container and water increase from external kinetic energy entering that system, but from the perspective of the universe the kinetic energy has stayed internal, and, therefore, no change.
Work deals with the mechanical transfer of energy between and within systems. Whereas heat deals with the movement of atoms and molecules through their collisions as they translate, rotate and vibrate, work deals with the directional force of atoms and molecules as they are applied to another object. Using a hammer to drive nails is such a form of work. In many instances, the execution of work generates both work and heat, just as the application of heat can be utilized for work.
In reality, since heat and work deal with the movement of atoms and molecules, the only real reason they are differentiated is for our sake. To distinguish it so that humanity may exploit the laws of thermodynamics for its benefit. When looking at the application of fundamental forces we see thermodynamics as merely a more complex application of the electromagnetic force. The dispersion of energy through entropy, and the compulsion of electrons to be given or shared; impacting the charge and polarity of molecules, are just the attractive and repulsive interactions of the electromagnetic force through the light-speed exchange of photons.
Entropy is an important concept to understand but is also a tough one to define as in many cases people just say that it something akin to dispersion or dissipation of energy. Entropy, for lack of a good definition, deals the disorder within a system. Within the contents of a system, like our universe, the more uncertain the arrangement of the atoms the higher its level of entropy. Water in its liquid phase has higher levels of entropy than in its solid phase, and even higher levels of entropy when in its gaseous phase since the molecules are moving around more freely and therefore can achieve more possible arrangements. Ice has to take a crystalline structure when forming a solid, as other solids do, and that means fewer opportunities for variability. As a law of thermodynamics, the entropy of the universe will only ever increase or remain the same, never decrease.
Enthalpy is a little easier to understand when compared to entropy. Enthalpy is the sum of internal energy added to the multiple of pressure and volume. While the math behind how enthalpy is calculated isn't necessarily crucial for our discussion, the principles behind it are. Since energy isn't created or destroyed, it merely changes form; enthalpy allows us to determine what within a system changes. For example, in a closed system, with no external energy entering that system, for one of the factors to increase one or both have to decrease, and vice versa. Since the universe contains all the energy of the universe, obviously, and the universe is expanding in all directions, that means that the volume of the universe is increasing. For enthalpy to stay the same, the internal energy and/or pressure have to decrease. Pressure is indeed decreasing as the distance of galaxies expands along with the universe.
Equilibrium is the state in which the internal energy is balanced within a single or multiple systems. This means that in a system that is in equilibrium there isn't an unbalanced distribution of energy, and entropy is at its maximum level. Equilibrium will continue to be maintained until either energy is allowed to exit or enter the system. For example, you may put an ice cube in a hot bowl of soup in the hopes of cooling it down, and in the process trying to achieve a state of equilibrium where the ice cube has melted, and the soup has cooled to a steady temperature once again.
Understanding these terms allows us to now discuss the Laws of Thermodynamics, of which there are four, and what that means to the Theory of Everything.
Zeroth Law of Thermodynamics states that a system that is in thermal equilibrium with two or more other systems also requires that those other systems are also in equilibrium with each other. This is a thermodynamic interpretation of: if A is equal to B, and B is equal to C, then A must be equal to C. Simple, yes? Since equilibrium is achieved, no significant thermodynamic actions will take place until an external force impacts the system. The reason why it's called the zeroth law is that it was a fundamental concept that had to be included but wasn't the first to be established when the school of thermodynamics had its start. Hence this is the reason we have four laws of zero through three, instead of one through four. Somewhat superficial and initially confusing, but that is what psychists determined would be best.
First Law of Thermodynamics discusses that conservation of energy, in that when energy passes from one object to another, that the energy is conserved; though it may take new forms. In this way, you may apply an external force to a system, and the energy from that force will be transferred to the system in question. So when you punch someone in the face, a thermodynamic form of work, the force of that punch sees its energy transferred into the body of the other person — those molecules of the exterior flesh that took the force transfer that energy to adjoining tissues. Like a ripple on a pond, that energy is transferred throughout the body until it is effectively dissipated, both transferred throughout the rest of the body, as well as transferred out of the body to the surrounding air and the ground.
Second Law of Thermodynamics states that the entropy of all systems that interact with one another increases over time never decreases. Since entropy relates to the degree at which atoms may occupy any position within a system, this law says that the chaos of systems is always becoming more chaotic on average. When your freezer attempts to reduce entropy inside by decreasing the temperature the energy expended to do so increased entropy in the outside environment more so than it did inside, hence the reason why the back of the freezer is hot. It is expending energy and increasing entropy outside so that it can reduce entropy inside. So when you see entropy decreased in the environment; lakes freezing over, your soup getting colder, clouds forming from vapors, then the only reason this can happen is that there are thermodynamic systems that are increasing entropy elsewhere so that they can decrease entropy there to a lesser degree.
Third Law of Thermodynamics states that as the internal energy of a system comes closer and closer to reaching zero then so too does the value of entropy. Entropy, in all its chaotic nature, is a product of energy in some form. This law means that when you remove energy from the system then entropy also drops. Absolute zero temperature, in which no atoms and molecules are moving and interacting with one another, would result in an entropy level of zero. That is because entropy requires that these particles be able to occupy multiple positions, but without energy for them to move to those positions you won't have entropy.
So with the laws of thermodynamics laid out, we can make some generalizations. All energy is conserved, though it may change its form, and that the entropy of those systems expending energy will increase over time. All around you, you will see this occurring. If you are inside a building, you will see lights and televisions, and hear the music, machinery, and appliances. If you are outside you may see the sun and stars, feel the wind blow, and sense the temperature in the air. All these are systems that derive their energy from other various thermodynamics systems.
For example, electricity used by TVs, and other electronics, come from a source which generates its power through thermodynamic engines, such as:
- The kinetic energy brought on by water flowing through a hydroelectric turbine as a result of gravity.
- The kinetic energy brought on by wind flowing through a wind turbine as a result of a heat engine of atmospheric differences caused by the sun's radiant energy.
- The chemical energy brought by the burning of fossil fuels which boils water to spin a turbine in a heat engine.
- The potential energy released by photovoltaic cells when photons from the sun force electrons loose.
- The chemical energy released from a battery charged by the mechanical energy of a human using a hand crank generator who in turn converted the food they ate into chemical energy for their muscles.
And what does the TV do with the energy? It uses it to project photons into diodes, cells, and plasma (whichever method the TV was designed to employ) which alters them so that they radiate photons at specific wavelengths that our eyes can detect, and our brains can process and perceive. Even with all this intentional use of energy, entropy increases as some energy is lost to our process, but not lost to the universe. Using the hand crank generator as a source of energy, some of the energy is lost to friction and isn't able to convert all of its work into further work and heat that we use. Some are lost as heat and is dissipated away to surrounding atoms. With friction, energy is lost when a person's arms rub against their clothing and torso as the crank is turned. With heat, muscles generate heat during the chemical processes required to activate those muscles which is then radiated throughout the body to the surrounding environment.
Even the TV itself expends energy needlessly. Not just in the form of heat, as especially those CRT TVs produce a lot of heat, but also when it radiates lights. The purpose of the TV is to emit light and audio waves so that our eyes and ears can make use of it. But they are designed to emit light and sound omnidirectionally so this means that photons and vibrations are being sent everywhere. It takes just as much energy to send photons and vibrations to your eyes and ears as it does to that wall just next to your head. But usually, within any given room the volume of the room is taken up mostly by inanimate objects absorbing and reflecting those waves instead of eyes and ears to see and hear them.
With all processes, there is some energy loss within and throughout systems since they are converted and expended elsewhere; such as the atmosphere, the ground or objects, where it serves no useful purpose for humanity. Entropy, therefore, increases as some energy being used is lost to the system, but adds to the randomness that is the universe.
For the length of human history, the forces that dictated thermodynamics weren't completely understood. Does the element of fire reside within the wood and is coaxed out by the presence of heat or another flame? When I consume the flesh of plants and animals does their life force sustain me? Humanity makes an effort to understand the complexity of the world in simple terms like these for two reasons, one, we don't like uncertainty, and two, it works for our purposes. Just like we don't fully comprehend the nature of the gravitational force, the Theory of Relativity, give us workable formulas that allow us to put satellites in orbit, send crewed missions to the moon, and probe distant planets, moons, and asteroids. Our ancestors didn't need to know that fire and sustenance both work on potential chemical energy as a complex application of the electromagnetic force. You eat food, and you feel energetic. You don't, and you feel lethargic and slowly waste away. You rub sticks together fast enough or strike certain rocks or metals together, and you can make fire. Let the fire grow, and it makes more and more fire. Finding reasons for why this is the case is merely a means to relieve that uncertainty.