Family of Thermodynamics - Fundamental yet Impactful

So, why that old aged Mr. Thermodynamics, huh? I have been pondering about laws of thermodynamics for quite some time, at least I want to dive into both superficial and deep implications of laws of thermodynamics. Thermodynamics is all around us, from the obvious applications in car engines and refrigerators, to even the way haze spread around (haha, sorry for taking in haze example, but the widespread of haze is closely related to thermodynamics, and we shall see it later). In this blog, I will generally focus on second law of thermodynamics.

Okay, I will start off by giving a very brief definitions on the basics of thermodynamics, by expressing it in both technical wordings and layman terms. Here you go:

Technical and Formal

1.) Zeroth Law of Thermodynamics -  If two bodies are in thermal equilibrium with a third body then the first two bodies are at thermal equilibrium with each other.
2.) First Law of Thermodynamics - The total energy of an isolated system is constant despite internal changes.
3.) Second Law of Thermodynamics - Mechanical work can be derived from a body only when the body interacts with another at lower temperature; any spontaneous process will result in increase in entropy.
4.) Third Law of Thermodynamics - Entropy of a substance approaches zero as its temperature approaches absolute zero.

resources: http://wordnet.princeton.edu/

Family of Thermodynamics, in mathematical form, written by myself on my whiteboard

Layman and Informal

1.) Mr Zero - We give each other heat in equal amount, if we have equal temperature (All are equal).
2.) The No. 1 guy - Energy is a stubborn kid, prefers to always be constant in his life, although energy can change in different costumes, its attitude never change. (You can't get energy for free).
3.) 2nd Brother - Your stuff will only get messier, never tidier.
4.) 3rd Little Brother - The more you are chilled and calm, the less you want to mess around with people.

resource: myself

Mr Zero

Okay, enough of these whole bunch of definitions, we shall focus on its impact on our surroundings. Start with Mr Zero in the thermodynamics family. Mr Zero is more fundamental and obvious in our daily life experience. Imagine immersing yourself in hot, lukewarm and cold water, you can immediately tell that whether heat flows into your body, no net transfer of heat in and out of your body or heat generally flows out from your body. Its impact has been used almost in all mechanical devices, yes, Mr Zero is fundamental and impactful, and I will not elaborate too much with Mr Zero.

The No. 1 guy

No. 1 guy, sure, is stubborn. The total energy in our universe is always constant, regardless to its form. In layman words, No. 1 guy promises to change himself, but he only changes his costumes (forms) without actually changing himself (the total energy in a system). In first law of thermodynamics, the change in internal energy is often converted into net heat transfer into or out of the system and the net work done by / on (note the difference) the system. Hence, all energy is conserved. Implication and application? Yes, look at your refrigerators, car engines, air conditioner, etc. All these devices work based on The No. 1 Guy in the Thermodynamics family. In the sense of cosmology, the universe will always have the same amount of mass- energy (due to mass-energy conservation in Einstein's E = m c^2), but the universe, which is always with its constant energy available, is still vulnerable to its fate of 'death'. This 'death' concept of universe will be discussed in our dear nasty 2nd Brother. But still, I'm more interested in the 2nd brother, who is mysterious and new to many high school students or even layman readers.

The 2nd Brother

He is your messy guy, he always mess around with others. In formal words, second law of thermodynamics states that entropy (the measure of disorder) of a system will never decrease (as implied by the image I have uploaded). So, the concept of entropy can be new to many readers. Here is the thing, when you accidentally break your glass, you increase the entropy of the glass (or the glass you look messier, of course). Now, I will refer back to the spreading of haze into the second law of thermodynamics, a link of concept which might not be obvious to layman readers. Imagine gas in a container, before the cap of container is removed, all the gas molecules are kept in container, so the number of ways and free space of in which the gas molecules can move is restricted. Imagine removing the cap, or increase the space for the gas molecules to move in the piston, there will be more space available for gas molecules (and hence, more directions). Hence, the movement becomes more random (with more free space) and with the increase in randomness, the disorder of the system increases (and hence increase in entropy). Same example of observations of spreading of haze and dye is linked to 2nd law of thermodynamics, The 2nd Brother.

For a piston, an increase in space increases the direction in which gas molecules can move, and hence the movement of gas molecules become more random.

Spreading of Dye, an artsy image, it is also a phenomenon associated with concept of entropy

The 2nd Brother has another nickname, the Death God to the universe. Why such mysterious and disturbing name? Well, second law of thermodynamics is a death warranty to our dear universe. The entropy of the universe will always increase and never decrease. Observe our surroundings, apples decay, metals rust, all credit goes to our dear 2nd Brother in Thermodynamics family that only allows things to get messier (increase in entropy). Now, general readers with interest in science do know that our universe is expanding, and hence there will be more space available to the same amount of energy in the universe. This cases energy to be more disperse and spread out and hence the increase in entropy (an explanation offered earlier on how the  entropy increases when space increases). Even in charcoal, when we burn out our charcoal, the charcoal will turn into a less usable form in dust, with less useful energy available. So imagine stars in the universe being the charcoals, when stars get burnt out, its content is less usable and less heat can be obtained from aging stars that is approaching to its death. New stars will form at slower rate than old aging stars die because there will be less usable gas form available in the universe due to increase in disorder (entropy). With the expansion of universe and slower rate of formation of stars, the increase of disorder and entropy in universe sentenced death to out universe in hundreds and trillions years to come. Our universe will eventually become a cold place where the light emitted by stars will be less and less. And, hence a nasty name to 2nd brother in thermodynamics family.

3rd Little Brother

He is the little brother who looks a lot similar to 2nd brother, and 3rd law can actually be derived from 2nd law (will not elaborate the mathematical details here). His impact? This brother forbids absolute zero temperature (together with second brother). Why? Combining 3rd law and 2nd, you shall see that entropy (disorder) can never decrease and hence the temperature can never get down to absolute zero. In absolute zero temperature, all kinetic energy will be abstracted out of a system, and hence you make something in total stillness. This can't happen, it is forbidden by our Mr. Uncertainty (Heisenberg Uncertainty Principle). In formal words, Heisenberg Uncertainty Principle states that you can never know position and momentum of a particle at the same time. There is always uncertainty about the positions of molecules. Hence, by lowering a molecule's temperature to absolute zero, you are making it in total stillness and you can determine with certainty on where the molecules is and its momentum (momentum being zero). This is forbidden in quantum mechanics, a family of laws in physics.  

The Conclusion

In all our families of thermodynamics, we see that these laws affect us in both macroscopic and microscopic scale, ranging from simple daily life observation with spreading of dye to the death of universe. Physics, in all its implications, is beautiful. I have to admit that The Family of Thermodynamics, after all, is really fundamental and impactful. Hope you enjoy reading and have a nice day ahead.