This is not to say that science is easy to grasp with concepts (like atoms, molecules, photons, cells, etc.) that are not immediately visible. Remember that each scientist has to work at understanding concepts. Nothing is for free! Why do I bring this up? As you will see in the paragraphs below, there exist many scales by which to understand the world around us. Everyone at least should have the pleasure of understanding that the scales exist. At least, that is the position that I choose to take.
Boiling Water - Simple Right?
The process of boiling water is pretty simple at first sight right? Just add water to the sauce pan and set on the stove top -- apply heat. Simple. Oh, and wait until you hear the familiar sound of the water boiling or see the bubbles emanating (rising up) from the water toward the surface of the water in the sauce pan.
To most people, this is a process that is routine in order to start cooking a variety of meals. Some people carry this task out without even thinking about what is actually happening inside the sauce pan. But what if we wanted to think of the process in terms of a chemist analyzing the heating process of boiling inside the sauce pan. First, a proper definition of boiling is needed.
Since we started off with a description of boiling water in a sauce pan (a picture that is commonly seen in the kitchen), the next level of detail (scientific description) might be shown from "Wikipedia." Below is the opening paragraph for the entry of "Boiling" taken from "Wikipedia" and serves an intermediate description of the process of boiling water:
Boiling is the rapid vaporization of a liquid, which occurs when a liquid is heated to its boiling point, the temperature at which the vapor pressure of the liquid is equal to the pressure exerted on the liquid by the surrounding atmosphere. There are two main types of boiling; nucleate boiling where small bubbles of vapor form at discrete points, and critical heat flux boiling where the boiling surface is heated above a certain critical temperature and a film of vapor forms on the surface. Transition boiling is an intermediate, unstable form of boiling with elements of both types. The boiling point of water is 100 °C or 212 °F, but is lower with the decreased atmospheric pressure found at higher altitudes.
Why did I state that the above excerpt would serve as an intermediate description of the boiling process?
The reason is quite simple. Because there exists no mention of the water molecules that make up the liquid that is being heated to the boiling point. Additionally, at the boiling point as stated above, the pressure (vapor pressure) on the liquid by the atmosphere is equal to the pressure in the liquid. Therefore, molecules are free to escape into the vapor form. Of course, at this point, the number of molecules escaping depends on the concentration of the vapor. There exists an equilibrium between the liquid and the vapor above the liquid. Here is an excerpt to clarify the relationship between a liquid and the vapor pressure above the liquid taken from "Wikipedia" -- "Vapor Pressure":
Vapor pressure or equilibrium vapor pressure is defined as the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in a closed system. The equilibrium vapor pressure is an indication of a liquid's evaporation rate. It relates to the tendency of particles to escape from the liquid (or a solid). A substance with a high vapor pressure at normal temperatures is often referred to as volatile. The pressure exhibited by vapor present above a liquid surface is known as vapor pressure. As the temperature of a liquid increases, the kinetic energy of its molecules also increases. As the kinetic energy of the molecules increases, the number of molecules transitioning into a vapor also increases, thereby increasing the vapor pressure.
And the corresponding diagram which I found extremely useful also taken from the "Wikipedia" page is shown below:
Source: By HellTchi
As you can easily see, that there exists an "equilibrium" of molecules (indicated by red dots) in the diagram above. What does this mean? Equal number of molecules are going into solution (into the liquid) as there are leaving the solution (liquid) -- hence the "equilibrium state."
Upon reaching the boiling temperature of a liquid in a sauce pan, the "equilibrium" can be shifted in a certain direction. Meaning, more molecules can escape if the system is open. In the above diagram which was taken from the website "Wikipedia" there is a box around the diagram -- which indicates that the above diagram is a "closed system" in equilibrium.
If the top of the container were opened to the atmosphere, then water molecules would escape. If you have ever boiled water for a long duration of time without refilling the water, then eventually, the water in the sauce pan would disappear. The heat is driving the equilibrium in addition to the fact that the vapor (gas above the water) is diffusing into other areas of the kitchen and house. The water liquid in the sauce pan is trying to form an equilibrium with the entire atmosphere (the space of the house). Wow! Think about it.
How does a chemist think about boiling water then?
Now that the process of boiling water has been properly defined, lets look at an example of a chemist looking to "model" the process going on inside of the sauce pan. I borrowed an excerpt from an article out of the website "R&DMag.com" titled "Researchers Study Three-Way Battles In The Quantum World." Here is the excerpt below:
When water in a pot is slowly heated to the boil, an exciting duel of energies takes place inside the liquid. On the one hand, there is the interaction energy that wants to keep the water molecules together because of their mutual attraction. On the other hand, however, the motional energy, which increases due to heating, tries to separate the molecules. Below the boiling point the interaction energy prevails, but as soon as the motional energy wins the water boils and turns into water vapor. This process is also known as a phase transition. In this scenario the interaction only involves water molecules that are in immediate proximity to one another.
Do you think about that while staring into a pot of water that is arriving at the boiling temperature? The above excerpt was to prime the reader about the ongoing fascinating research by the Quantum Electronics group at ETH Zurich. Specifically, using a laser beam the group managed to trap in a "lattice" a few rubidium atoms. By controlling the frequency of the lasers, there was control (or a monitor) of the rubidium atoms that might enter and exit the "lattice."
Why was this important? As mentioned in the pot of water example, the "long-range" interactions were previously thought not to contribute to the process of boiling. Now, with refinements in both "modeling" and experimentation, the group was able to study the long range interactions. The work is a good step in the right direction to studying unique properties of liquids in complex environments.
The significance is stated by the authors as follows:
"Using this trick we now have three competing energy scales in our system: besides the motional and interaction energies there is, in addition, the energy associated with the long-range interaction", explains Landig. "By varying the motional energy and the long-range interaction energy, we are able to study a number of novel quantum phase transitions."
Having a better understanding of phase transitions will be critical in our ability to study certain scales. What is meant by this? Typically, we live on the "Classical https://en.wikipedia.org/wiki/Classical_physicsScale" -- the scale where we study objects like
Most people do not.
Adding Pasta To Boiling Water!
Now that you have had an introduction molecules and atoms -- so far as these concepts apply to the example above -- which was the boiling pot of water, lets make a complicated system into an even more complicated system. I have yet to read the book titled "The Wonders Of Physics" by the author Dr. so and so. I found a few excerpts which swayed me into purchasing the book.
Yes, I have a large amount of mental debt. That is what I refer to as having too many books in the queue to read. On my shelf at home along with books on another shelf at my office, there are two stacks of books -- that I am reading. Yes, I can read multiple books at once. No, I am not special. My grandmother passed the ability to do so genetically -- I found out in my early 30's -- when I encountered her multiple stacks. Anyways, here is an excerpt that has relevance to the discussion of cooking pasta that was taken from his book:
The authors take the science a step further than I had previously done with the above description taken from the article in laboratory magazine. Well written and succinct to the level of detail with which can drive thought among a chemist about the various factors involved in the chemistry of cooking. Of course, to a chemist, the process of cooking is traditionally reduced to a "reaction" which produces a "product." The recipe dictates the conditions under which the "reaction" will take place to produce the desired "product" -- your meal.
Chances are the next time you eat a meal, you will have a thought regarding the chemistry behind the "reaction" needed to produce the meal. If you choose to learn more about the topic, maybe in the future, you can switch professions and become a chemist working on the problem of pasta's for a company like "Kraft" that sells pasta products. Chemists are needed to fill these positions.
Prior to reading this blog post, you might have just thought that non-chemists were the people responsible for coming up with the wonderful recipe that produces the meal that you desire. The initial cooking recipe might have been started by a non-scientist. But if a company produces the product and tries to optimize the product, chances are the there is a "food scientist" behind the process (Research & Design). Food science is a huge field worth exploring.
Going back to the excerpt above, I am amazed at the level of detail at which "food scientists" work at. Understanding the composition of pasta and the relevant parts that the components play during the cooking process (heating pasta in boiling water) is fascinating. I cannot wait to read the book. Maybe I will have to move that particular book to the top of the pile of "books to read."
Furthermore, I will have to investigate how the authors came up with the detailed explanation of the formation of "gluten" when heating the pasta. Why is this important? Currently, there is a large push in food industry to provide "gluten free" products. I have been curious about this emerging trend. Seems like the chance of not seeing a sign out in front of food vendors in Los Angeles labeled "Gluten Free" is near impossible. I always wonder -- what does that mean?
According to the above excerpt, "glutenin" and "gliadin" along with water form a network (or net) that is termed "gluten." Gluten is responsible for the rise and elasticity of the bread as indicated on the "Wikipedia" page for "gluten":
Gluten (from Latin gluten, "glue") is a mixture of proteins found in wheat and related grains, includingbarley, rye,[1] oat,[2] and all their species and hybrids (such as spelt,[3] kamut, and triticale[3][4]). Gluten giveselasticity to dough, helping it rise and keep its shape and often gives the final product a chewy texture.
The properties of proteins are responsible for incorporating these ingredients into food products such as breads, pastas, cereals, etc. Chemistry is amazing. If we want to further understand which ingredient is playing a certain role, scientists have uncovered that too with the following excerpts for "glutenin" and "gliadin" from their respective "Wikipedia" pages:
"Glutenin":
Glutenin (a type of glutelin) is the major protein within wheat flour, making up 47% of the total protein content. The glutenins are protein aggregates of high-molecular-mass (HMW) and low-molecular-mass (LMW) subunits with molar masses from about 200,000 to a few million, which are stabilized by intermolecular disulfide bonds, hydrophobic interactions and other forces. Glutenin is responsible for the strength and elasticity of dough.[1]
And, next is "Gliadin":
Gliadin is a class of proteins present in wheat and several other cereals within the grass genus Triticum. Gliadins, which are a component of gluten, are essential for giving bread the ability to rise properly during baking. Gliadins and glutenins are the two main components of the gluten fraction of the wheat seed. This gluten is found in products such as wheat flour. Gluten is split about evenly between the gliadins and glutenins, although there are variations found in different sources.
Imagine the research that went into investigating that out of the many different proteins in wheat along with other cereals, the research narrowed down to two proteins: glutenin and gliadin. I wonder what the spectroscopic signatures of these two proteins are? How was the research carried out to narrow down to these two proteins? How were the proteins characterized? That is another topic for another blog.
Where do we go from here with this blog post?
How About A Conclusion?
Lets recap on the underlying message so far in the blog post. First, simple processes like cooking can be extremely complicated depending on the scale of viewing. With respect to the problem of cooking pasta the following has been shown. If you are considering the macroscopic scale, then you might be concerned with consistency or smoothness, or softness of the pasta along with the temperature at which you are cooking the pasta. Furthermore, if you are cooking the pasta at different altitudes or environments, the recipe might change. What about if you are looking at the process from the eyes of a chemist or food scientist?
If you are viewing the problem (cooking pasta in boiling water) as a chemist, there are different scales at which to think about the problem. On the microscale or even nanoscale, you have these molecular systems in a complex environment. Establishing a vapor equilibrium with the environment above the liquid. If that environment is closed (e.g. having a saucepan with a lid on it), then refilling the water might not be necessary. The liquid will establish an "equilibrium" with the "headspace" of vapor above the liquid. There might be visible water droplets on the lid of the saucepan -- which after growing to a certain size will be overcome by the force of gravity and drop back into the boiling water. At that point more water molecules will escape into the "headspace" between the liquid and the lid to establish an "equilibrium" state at that temperature and pressure.
What about an open sauce pan of boiling water?
Upon boiling, the system which is made up of gas and liquid will still try to establish an "equilibrium" with itself. The problem is that the system is open. Which means that the liquid in the pan will establish an "equilibrium" with the entire house -- as the water vapor diffuses throughout the rooms of the house. Diffusion occurs due to having a high concentration of water vapor in a small area and a lower concentration throughout the house. There is something to think about -- that will occupy your mind for a while.
Thinking like a scientist is not a decision -- once you have been exposed to the concepts. You might be able to get away with ignoring the concepts when viewing the environment around you for a short time. Why would you want to do that? Do the concepts above give you a headache? No worries if they do. Understanding the concepts behind science take time. That is why education is a life long learning process. As highlighted above, every day, new ideas and concepts about the world are emerging and in every greater detail. Again, this is why learning science should be fun and entertaining and also a life long pursuit. I hope that you never look at a boiling pot of water the same way ever again. Until next time, enjoy the day!
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