Lost in the forest of science.

The study of science begins for everyone as a small path in the forest of ignorance, but with effort and experience, this path becomes our personal path of knowledge and information, opening up many possibilities. Albert Einstein, like everyone else, started out in the woods and proved that getting out is worth it, not just for him, but for all that his knowledge did for humanity. Science is not for everyone and few Einsteins exist. Sadly, many get lost, confused and frustrated, giving up before they can utter their first “Eureka” when a jewel of knowledge falls into their place. Those “Eureka” moments can excite us to continue on our particular path.

So the first step is to be motivated and want to know more.

The next important step is to pay attention to the definitions: something that is important in all areas: in sports you have to know the rules to play the game: it is the same for science. Knowing the definitions clears up confusions and applying them (solving problems) solidifies them. Over time, the scientific method and thinking become a way of life, allowing you to understand many situations, even outside your particular area of ​​expertise.

With emergent structure. For example, life sciences and medicine are based on biochemistry and pharmacology, which is based on organic chemistry, and organic is based on physical chemistry. Physical chemistry rests on top of physics, and mathematics is the logic that unites them all.

Along the way there are many things on the sidelines, too numerous to list here: new materials and nanotechnology are two important and well-known disciplines. Also several areas overlap in multidisciplinary fields, such as physical and organic chemistry (physical-organic chemistry); organic synthesis and chemical kinetics (organocatalysis), inorganic and organic chemistry (organometallic chemistry): the list goes on and on.

Clearly, no one can become an expert in all of these areas. However, a good foundation in the basic physical sciences allows one to at least be in a position to appreciate the work of others in the many areas of scientific endeavor. You could end up as a lawyer, social worker or in finance. A good scientific background will help the lawyer defend his case of, for example, patent infringement; it helps the social worker understand the side effects of medications a client might be taking and enables the financier to make smart decisions about whether to invest in one mining company or another.

On the other hand, you could become a scientist, which will lead to many interesting careers.

scientists and engineers

Science can be divided into two broad categories: fundamental science (research) and application of those ideas (engineering: also called research and development (R&D)). Today there are about ten times as many engineers as scientists. It takes more effort and more people to take fundamental ideas developed by a few and turn them into technology that we use to improve our quality of life.

Think of the automotive industry. The internal combustion engine, based on the Otto cycle, was developed by a few (who proved it worked), and then many engineers took that basic idea and over the last hundred years developed the cars we have today.

To be a good engineer, you have to start with the fundamentals and learn the basics before you can apply them.

The macroscopic and the microscopic

A broad division of science is macroscopic (a sample large enough for us to measure and examine) and microscopic (atoms, molecules, and collections of these too small to observe individually).

There are two great pillars of macroscopic science: thermodynamics (the study of heat, work, and efficiency) and classical mechanics (Newtonian physics that describes the motion of macroscopic objects).

The microscopic is governed by quantum mechanics.

Since microscopic particles have a lot of symmetry, the field of group theory (a mathematical topic) should be mentioned. This helps to visualize molecules and reactions, and has special relevance in the most fundamental science, which is physics. You don’t have to be a mathematician to use group theory. Mathematics is a tool of scientists: logic guides us.

The field of Statistical Mechanics relates macroscopic objects to their microscopic particles.

The example of chemistry.

Chemistry is the study of bond making and bond breaking, that is, chemicals react to form different chemicals. A chemical reaction proceeds if the conditions are right: two important conditions are energy and entropy. Both are substances and entropy is as tangible as energy. How did this come about?

Engineers started noticing things a couple of hundred years ago: like horses that walked in a circle and drove the cannon-boring machinery. The horses walked at a steady pace (constant energy), but a blunt bit produced a lot of heat and not much work (piercing the barrel was slow), but a sharp bit produced much less heat and more dullness. This is the First Law of Thermodynamics:

Energy (horsepower) = heat (friction) + work (gun).

It is clear that energy is not cheap (horses have to be bought, fed and cared for) so it would be better to reduce heat loss and increase work done. That is, efficiency in the use of energy has become an important consideration.

In the 19th century, thermodynamics evolved further out of the need to increase the efficiency of the steam engine that fueled the industrial revolution. The first steam engines had an efficiency of around 3%, so improvements were definitely needed. Adding a second cylinder, for example, made things a lot better, but could they do more? Could the dream of 100% efficiency, i.e. perpetual motion, come true?

This led Sadi Carnot in the 1830s to define a cycle for the steam engine from which entropy was discovered and the second law of thermodynamics established: perpetual motion was shown to be impossible. The Otto cycle was developed for an internal combustion engine some forty years later.

Although alchemy is an old subject, it was only after the First and Second Laws of Thermodynamics were developed that chemistry really took off. Many were involved in its development. Besides Sadi Carnot, some notable names are James Maxwell, Rudolf Clausius, James Joule, Willard Gibbs, and Ludwig Boltzmann.

The ideas they developed apply well to chemistry. When the links are broken, energy must be added to the system; and when bonds are formed, energy is released to the surroundings. Some chemical reactions produce more randomness (higher entropy) and sometimes more order (lower entropy) as the atoms rearrange to form products. Both energy (heat and work) and entropy (randomness) play important roles in the spontaneity of a chemical reaction.

Here is an example. Trinitrotoluene (TNT) can explode (a rapid chemical reaction). From the chemical formula it has three nitrogen bonds. By the way, most chemical explosives contain nitrogen. Combustion of one mole of TNT releases 3400 kJ mol-1 of energy,

C7H5N3O6(s) + 21/4 O2(g) à7 CO2(g) + 5/2 H2O(g) + 3/2 N2 (g) †H = -3,400 kJmol-1

Compare this, however, with the energy of burning sugar as sucrose (a slow chemical reaction),

C12H22O11(s) + 12 O2(g) à12 CO2(g) + 11 H2O(l) †H = -5.644 kJ mol-1

Sucrose produces much more energy per mole than TNT! So why isn’t sucrose also an explosive? Sucrose burns slowly relative to TNT, with a corresponding slow release of carbon dioxide. TNT burns so fast that a lot of energy is released in a short amount of time. Also, solid TNT occupies a small volume, but the final volume is equal to 11 moles of gas (about 250 liters in STP). The destruction is caused not so much by the heat released but by the rapid expansion of the gases produced. Using the First Law, the energy released by one mole (3400 kJ) is converted to some heat, but a lot of work is done on the surroundings as the gas expands, and this can cause damage.

This is where entropy comes in. Notice that the right side of the TNT combustion has only 21/4 = 5.25 moles of gas, while the RHS has 11 moles of gas. This means that there is more disorder in the RHS than in the LHS. Clearly the rapid expansion in the explosive combustion of TNT can lead to destruction (it would knock Humpty Dumpty off his wall) and cause more disorder and thus increase entropy. Both energy and entropy are favorable for this reaction to occur. This is not always the case, especially in biological processes, where entropy, not energy, is the primary driving force.

Thermodynamics tells us which chemical reactions will occur and which will not. Chemical kinetics tells us how fast those reactions take place and how much energy is needed to start a reaction. TNT is not very sensitive to hits because it has a high activation energy. On the other hand, Nitroglycerin, (NG), another chemical explosive (with many nitrogen bonds), explodes with a small hit and cannot be transported in liquid form at room temperature. It has a low activation energy. Alfred Nobel solved the nitroglycerin problem by inventing dynamite: reducing shock sensitivity by immersing GN in sawdust, paper, or some absorbent material. The patent was so successful that it left us the legacy of the Nobel Prize.

Equilibrium thermodynamics is a closed field today with no new fundamental research being done. It is a beautiful, complete and compact theory that gives the relationship between the macroscopic quantities that we can measure: energy, heat capacities, compressibility factors and many more, with wide application.

Thermodynamics is essential knowledge for all chemists. However, thermodynamics fails to explain why these relationships exist. This is given by another elegant theory called Statistical Mechanics.

Physical chemistry covers all of these.

There is much more to say, but that is a summary. Actually, many say that thermodynamics is not a good name because it describes equilibrium properties, not dynamics. A better name would be thermostatic, but nobody calls it that.