Fish Poisons for Anesthesia

I stumbled across a bizzarre video in my recommended videos feed on YouTube yesterday that shows a goldfish getting surgery on his head growth blocking his vision (Note: this video is not for people who are squeamish, although there is no blood):

The video was an interesting find overall, simply because it had no actual correlation with any videos in my watch history. I haven’t watched videos on fish or surgery, so to be recommended with a video featuring both was unusual. To be honest, while I was engrossed by the goldfish surgery, what made me keep watching was the maker, Colum’s Aquaponics’, use of clove oil to sedate the fish.

This brought two thoughts to my mind. The first was that clove oil has been recommended by traditional herbal medicine for toothaches. Typical application may have entailed chewing a clove or putting it between the gums and cheek next to the painful area. According to Colgate, clove oil has also been on the rise as a form of alternative medicine for oral pain in recent times as well [1]. Clove oil contains the chemical eugenol that is responsible for its anesthetic properties and is also used in refined form for modern dental applications [2]. Eugenol is a substituted guaiacol, making it related chemically to other plant compounds like vanillin though with very different effects [3]. Seemingly unrelated, this link between analgesia in humans and anesthesia in fish makes the use of clove oil to numb a surgery appear plausible to me, though a stretch.

Fig. 1: Eugenol, a fish anesthetic found in clove oil (Wikimedia)

The second was that in ancient Hawai’i, there was a method of fishing that involved lacing a stream or tide pool with a plant tincture to sedate the fish and cause them to float to the surface. The plants used included ‘ahuhu (Tephrosia purpurea) containing the fish toxin tephrosin and ‘akia (Wikstroemia oahuensis) [4(published in 1921, source must be treated as a work of its time),5]. Looking at some pictures of ‘akia on the internet, I immediately recognized the plant to have grown all over my elementary school campus back home. That’s pretty weird to think about, but it also makes me feel like I’ve missed out on an opportunity for some fun experiments.  

Fig. 2: 'Akia plant leaves and flowers ('Imiloa)

Hawai’i is not the only place to have practiced poison fishing, though in general the practice is considered destructive and paralleled to other wide-effect fishing methods like blast-fishing. And of course, the limited reach of poison fishing would be no match for the current global demand for fish. Yet while this fishing technique has been passed by in modern times, the plants and chemicals once used for fishing may now find new applications, namely in fish anesthesia for aquatic veterinary care.

I hope you enjoyed this short blurb on the interesting topic of fish anesthesia, and be sure to leave a comment and share your thoughts on the post. These past few weeks have been busy in school, and the first wave of midterms (UPenn doesn’t understand the term “midterm”) has started to hit. I do believe I will be able to post at least every other week, however, as seems to be my current posting schedule, so be sure to look out for future posts. As always, thanks for reading!  

Boiling Water at High Altitudes: A Representation of American Scientific Literacy

A recent survey by the Pew Research Center found that Americans are more likely to answer correctly questions related to basic science concepts than to scientific understanding [1]. Among the bank of questions, ones such as which layer of the earth is hottest and whether uranium is used in nuclear energy were answered correctly more often than ones such as whether the amplitude of sound waves causes its loudness. The question answered incorrectly most often was whether water at higher altitudes boils at lower temperatures with only 34% of respondents knowing that, indeed, it does.

Fig. 1: Results of Pew Research Center survey (Pew Research Center, same as reference 1)

Public scientific literacy is an important goal to work towards for developed countries. As Cary Funk and Sara Kehaulani Goo of the Pew Research Center posit, the ability to understand scientific concepts is crucial to people being well enough informed about current issues such as GMOs and the energy crisis to make educated decisions in the polls. Scientific literacy also makes daily life easier by finding more efficient solutions to everyday problems.

As a small step towards improving scientific understanding, let us discuss why it is easier to boil water at higher altitudes.

Liquid water and water vapor exist in a sort of equilibrium. There are a number of factors that can shift this equilibrium, but one we interact with daily is temperature. Say you spill a glass of water. Of course, a large spill would require immediate attention, but if only a thimbleful of water was spilt, some would be inclined to let it evaporate. Evaporation involves two main processes at play. First, the water is receiving kinetic energy from its surroundings in the form of heat energy. Second, the water is in higher concentration in the spill than in the spill’s surroundings and therefore a concentration gradient is formed at the water’s surface.

So what has this all got to do with boiling water? Well, water boils when transforming into a gas. Therefore, boiling water is a phase transition described by the equilibrium between liquid water and water vapor. Besides temperature, pressure also affect liquid-gas equilibrium as described by the ideal gas equation,

                  1.       PV=nRT (P is pressure, V is volume, n is number of molecules in moles, R is the gas
                   constant, T is temperature)

LeChatelier’s principle states that a system in equilibrium will move away from an induced change. In the case of an increase in pressure, we can see that if n and T remain the same then the ideal gas law describes a shift to decrease V, volume. On the other hand, a decrease in pressure should cause a shift towards a higher V. This means that at lower pressures, water prefers to exist in a gaseous state and the equilibrium shift will cause the water to boil. This is the foundational concept of rotary evaporators, which use the concept of reduced-pressure boiling to remove solvents.

Fig. 2: Deriving atmospheric pressure in atm's (Pearson)

Now all that is left is to link pressure to altitude, which isn’t too hard. By definition, atmospheric pressure is defined as the weight of the atmosphere over an area at sea level [2]. For example, one inch of land at sea level partitions a pillar of atmosphere weighing 14.7 lbs, so atmospheric pressure in PSI is 14.7 lbs/in². A logical extension of this concept would tell us that at any altitude greater than sea level, the pillar of air would be shorter and would consequently weigh less. This is the missing link we were searching for between pressure and altitude. Putting all of the above information together, we see that a decrease in pressure causes liquid water to favor boiling and that an increase in altitude causes atmospheric pressure to decrease. Therefore, water boils easier at higher altitudes.

Scaling the results of the survey to education levels, the Pew Research Center also found a correlation between higher education and scientific knowledge. But this is not a given. Even as college students, we must all work towards insuring that we are among the scientifically literate ready to contribute educated opinions to today's social debates.

Birthday Borax and An Explanation of Crystal Nucleation

For my birthday a while back, a friend of mine gave me food coloring, a box of borax and spools of thread. I asked what they were for, and she said crystals.

Fig. 1: Borax crystal growing birthday gift (orig.)

Of course! I hadn’t ever seen people grow borax crystals before, only sugar or salt, so I looked up a tutorial on YouTube. The procedure was pretty standard: heat water up to near boiling, dissolve the borax, insert a pipe cleaner or thread and wait overnight for the solution to cool down and precipitate out crystals. But while the procedure is simple, the science behind nucleation is more complicated and pretty interesting.

In order for a crystal to form in solution, molecules of a substance must conglomerate to an adequate size to encourage the spontaneous coordination of more molecules. A cluster of this adequate size is called a "nucleus," and the process of its formation is called "nucleation." Clusters that are not large enough to be nuclei are called "embryos." The nucleation process can be described in terms of Gibbs free energy, which accounts for both enthalpy, related to the nucleus’ internal energy, and entropy. Gibbs free energy is given by the equation

                      1.       ΔG=ΔH-TΔS (H is enthalpy, T is temperature in Kelvins and S is entropy)

For a newborn crystal born homogenously (meaning suspended in a medium without contact with other surfaces), there are two main energy changes that are occurring. The first is a lowering of molecular energy due to the formation of attractions between coordinating substance molecules for reasons described in Why Cold Drinks "Sweat". This change in energy can be describe by the equation

                  2.       ΔG=VΔG_v (V is volume, ΔG_v is the change in internal energy per unit volume)

To find ΔG_v, we will assume that the crystal-solution system is cooled to slightly below the substance's melting point, T_m. At this small undercooling, ΔH and ΔS can be approximated as temperature independent [1]. But first, at T_m the difference in free energy ΔG between a substance’s solid and liquid forms is 0. Therefore,

                                                                      3.       ΔG_m=ΔH-T_mΔS=0

                                                                      4.       ΔS_m= ΔH/T_m

Now, assuming that ΔH and ΔS are temperature independent, we can use the same expression for entropy as used at T_m to find the value of ΔG_v. While we’re at it, let’s assume the crystal nucleus is spherical for simplicity’s sake. The following are therefore true:

          5.       ΔG_v=ΔH_fv-TΔS= ΔH_fv-T(ΔH_fv/T_m)= ΔH_fv(T_m-T)/ T_m= ΔH_fvΔT/T_m (from equations 1 and 4)

          6.       ΔG=VΔG_v=4/3πr³(ΔH_fvΔT/T_m) (from equations 2 and 5, V_sphere=4/3πr³)

The second energy change occurring is an increase in a newborn crystal’s energy because the surface of the crystal is disrupting bonding in the liquid medium around it. This change can be described as

          7.       ΔG=Aγ_s=4πr²γ_s (A is the nucleus’ surface area, γ_s is the surface free energy value
           characteristic of the medium-solid interface)

This expression is just the disruption free energy per unit area multiplied by the surface area of a sphere. Together, these two energy changes dictate nucleation. Putting the two expressions together, we get

          8.       ΔG_hom=VΔG_v+Aγ_s= 4/3πr³ΔH_fvΔT/T_m+4πr²γ_s (ΔG_hom indicates that this equation is for
           homogenous nucleation)

This equation is very useful and can be used to describe nucleation events from borax crystals precipitating to homogenous cloud formation. To tease a little more information out of equation 8, let’s see how ΔG_hom changes in response to a substance clump slowly growing in radius. This rate of change corresponds to the derivative of ΔG_hom with respect to radius r [2];

                                                             9.       d(ΔG_hom)/dr=4πr²ΔG_v+8πrγ_s

The point where ΔG_hom no longer changes with r corresponds to the peak on the following graph of equation 8 and its component parts, equations 2 and 7.

Fig. 2: Free energy of nucleation as radius increases (Materials Science and Engineering, an Introduction)

Equation 2 is shown as a decreasing curve because ΔH_f is negative for crystallization. This makes sense because as a material crystallizes, energy is lost to its surroundings, so ΔH_f must flow out of the system. To find the critical nucleation radius,

                                           10.   d(ΔG_hom)/dr=4πr²ΔG_v+8πrγ_s=0 (from equation 9)

                                           11.   r^*=2γ_s/ΔG_v

Plugging the critical radius into equation 8 and extracting the negative from ΔH_f to avoid confusion, we get

                                  12.   ΔG^*_hom=-4/3π(2γ_s/ΔG_v)³ΔG_v+4π(2γ_s/ΔG_v)²γ_s=16/3πγ_s³/ΔG_v²

This expression describes the magnitude of the energy change needed to get a molecular cluster up to the size of the critical radius r^*, a sort of activation energy [3].

However, homogenous nucleation is relatively difficult compared to heterogenous nucleation, as I’m sure you’ve probably heard. Heterogenous nucleation occurs when a nucleus forms on a surface, such as a dust particle for clouds or thread for nucleating borax crystals. Because of the complexity of finding heterogenous nucleation equations due to complex volume and surface area terms as well as extra surface energy considerations, I will not be posting these calculations. The calculations can be found in reference 3, but the summarized result is that the critical radius in heterogenous nucleation remains the same as with homogenous nucleation while the nucleation free energy lowers and makes the nucleation process more accessible. This is why minimizing dust or rough surfaces is important for growing larger crystals rather than clusters of small ones.

What has been described above is just a small bit of the complexity of crystal growing. Knowledge of nucleation rates and crystal growth is widely used in processes such as tuning metals to have properties fit for specific purposes or growing single-crystal silicon for computer processors, and I’m sure this information will come up again on later posts. But mild difficulty of math aside, it’s cool stuff, huh? As a treat for reading through this post, watch this fun Minute Earth video on the homogenous nucleation of clouds and see if you recognize some of the concepts we discussed.

I’m planning on growing some borax crystals soon, and when I do I’ll likely write an experiment post about it so be sure to come back and check that out. I’ve already had my first few days of classes and so far it seems that I will be able to continue posting once a week, likely on Sunday or Monday. As always, thanks for reading and I’ll be posting new stuff soon!

Why Cold Drinks "Sweat"

With a horrible heat wave hitting the Philadelphia area, it’s good to think cool thoughts. Already feeling the heat last night, I left a coconut water in the freezer with the intent to drink it but forgot and so took it to work this morning frozen solid. I figured since it’s so hot outside and the metal can is a good conductor, it’d probably melt pretty quickly. And while the ice in immediate contact did melt, the inside remained frozen and I had to cut the top open with scissors to eat it. Before I figured this out, the can had already shed a puddle at my desk. Have you ever wondered why it is that cold things "sweat."

Fig. 1: My favorite coconut juice brand, Foco (pinstopin.com)

Most of us are familiar with the concept of condensation, having learned about the water cycle in elementary school. We are commonly taught in elementary that water exists as vapor at hot temperatures, condenses to liquid as the temperature drops and eventually expands (not condenses, as ice has a lower density than water due to hydrogen bonding) into ice as the temperature drops further. In high school, we learn about the ideal gas law and how pressure also affects phase transitions, yielding the phase diagram.

Fig. 2: Phase diagram for water (myhomeimprovement.org)

So from this standpoint, we are all familiar with why cold things "sweat." What else is there to it? While the basic principles stand, there are some other viewpoints from which we can view this phenomenon.

Phase transitions can be viewed as being an equilibrium process, as is demonstrated by the fact that an ice and water mix maintains a 0°C temperature. In such a mix, the ice melting and the water freezing are competing processes that are controlled by environmental factors; if you cool the mix the ice expands, but if heated the ice melts. Additionally, the entire mix must either become ice or water only before the temperature can deviate significantly from the equilibrium temperature of 0°C. What’s cool about this process is that if you track the energy entering the ice and water mix, say a glass of iced coconut water (let's treat this as an ideal glass of pure iced water), we can predict the corresponding phase transitions based on molecular kinetics.

When bonds are formed, whether strong or weak, we know that energy is released as heat. The reverse is true as well, breaking bonds requiring energy. The direction of bond energy transfer can be simplistically remembered taking into account the conservation of energy in a two molecule one-dimensional collision. Say two water molecules are moving towards each other and stick together upon impact. Where did the kinetic energy go? Ignoring molecular vibrations, the energy had to have been released as work, or heat. In order to separate the water molecules, we need to get them to move apart, a.k.a. add work, or heat, to yield kinetic energy. In our glass of iced water, this sort of energy transfer is happening extremely fast and on a large scale, one that can be described by Le Chatelier’s principle since the ice and water form an equilibrium.

Fig. 3: Ice-water equilibrium state (JVC's Science Fun)

Now let’s put the iced water outside on a hot summer Philadelphia day. From experience, we know that the ice will melt and the water will become unappealingly warm. If we track the direction of energy transfer, the higher energy hot air must be donating energy to the lower energy iced water simply because this is the default direction of energy transfer in our universe according to the Second Law of Thermodynamics. The added energy must translate into kinetic energy as temperature is positively correlated to molecular kinetic energy. From our two water molecule system we know that a decrease in water molecule association is predicted, favoring water over ice and vapor over water. This manifests as the ice melting and the water warming and eventually evaporating.  

What has been so far described, however, is only focused on the iced water itself. Let’s change our basis to focus on the hot air along the iced water glass instead (assume the water glass does not hamper kinetic energy exchange between air and iced water). Hot air carries a lot of water since at higher temperatures water enters the vapor phase preferentially according to Le Chatelier’s principle. From the viewpoint of the air, the cold iced water is pulling kinetic energy from it, accordingly cooling the air within a certain range of the glass. Plugging this information back into our two molecule system, the energy must be afforded by reducing the molecular kinetic energy of the air, increasing the probability of water existing in associated groups, i.e. water. And this is why a cold drink sweats in the summer.

Since school is starting up again, I will not be able to post as frequently as I have been during the summer. I will try to post at least once a week, and will probably be doing so during the weekend since this is when time is most available. Please have patience with me on this, and as always thanks for reading!

It's Just Plastic (But What IS Just Plastic)

I have a question for you. We use the stuff all the time, but do you really know what plastics are? I mean really know. I definitely didn't until this past year when I took a course on materials science that covered the nature of polymers beyond what is traditionally taught about just joining a bunch of monomers together into strings. So let’s take a closer look at a material that has revolutionized the modern age.

Plastic is a broad term for a number of synthetic polymers with varying structures, properties, origins and chemical compositions. The properties of plastics vary according to three major factors: chemical composition, tacticity and structure. Chemical composition as a factor is fairly obvious since the different types of plastic we make vary in make up. Composition affects properties of a plastic such as the range of temperatures in which it maintains its structure. Polyethylene’s (PE, No. {2,4}) melting temperature (T_m) is around 115-130°C while polypropylene’s  (PP, No. 5) T_m is around 130-170°C. The only difference between these two polymers is an extra methyl group every other backbone carbon in the case of PP. Chemical composition also informs how a polymer is produced. Polyethylene terephthalate (PETE, No. 1), the plastic most water bottles are made of, is synthesized through the transesterification of terephthalic acid and ethylene glycol while many other polymers such as PE, PP and polystyrene (PS, No. 6) are produced by free radical polymerization. Copolymers, or polymers made with more than one monomer type, also exist in a variety of forms (block, graft, random and alternating) with more limited usage.

Fig. 1: Free radical polymerization of PS (California State University, Dominguez Hills)

Polymer tacticity is another property of plastics, but one you usually don't hear about. Tacticity relates to the organization of monomer units within polymer strands. There are three categories of polymer tacticity: isotactic, syndiotactic and atactic polymers in order of increasing variability. Isotactic polymers are comprised of monomer units all connected in the same way to each other. Syndiotactic polymers have every other monomer unit in the same orientation and atactic polymers are oriented any which way.

Fig. 2: Isotactic, syndiotactic and atactic polymer models (University of California, Davis)

Different synthesis methods affect the tacticity of the produced polymer,  for example the use of metal-catalyzed polymerization reactions may enact more stereospecific polymer synthesis [1]. Tacticity mainly affects whether or not a polymer can form crystalline regions. Isotactic PS, for example, is more likely to form crystalline regions through pi-stacking than atactic PS is. Plastic performance is also sometimes affected directly by tacticity, as with isoprene rubber. Natural isoprene rubber is isotactic in that it is comprised entirely of cis-double bonds, which make it springy. Atactic isoprene rubber or isotactic trans-polyisoprene rubber are relatively unspringy [2].

A plastic's three-dimensional polymer structure has a lot to do with the macroscopic properties of a plastic. Polymers exist as spaghetti-looking chains of controllable length that bundle and stack into a giant mess. Each chain can be linear, branched, dendritic or cross-linked to other chains. When pulled upon intensely, linear polymer chains slide out from underneath each other and cause plastic deformation. Branched or dendritic polymer chains can make this harder to do, and cross-linked polymer chains, like vulcanized isoprene rubber, can be extremely hard to plastically deform (not a pun, I swear. It’s a type of deformation, along with elastic, related to a material’s tensile strength).

Fig. 3: Some possible polymer morphologies (Nature)

But if this is true, why does high-density polyethylene (HDPE, No. 2), made of linear polymer chains, have a lower tensile strength than its cousin branched low-density polyethylene (LDPE, No. 4)? This is due to crystal packing. When polymer strands organize, they form microcrystalline regions surrounded by amorphous, glassy regions.

Fig. 4: Crystalline and amorphous polymer structure (Polymer Science Learning Center)

Being linear allows HDPE to organize into a higher crystalline content than LDPE, and the extra intermolecular forces associated with these crystalline regions makes HDPE harder to deform than its other form. Fun fact, polymer crystallinity also has an effect on opacity in the same way the amorphous nature of glass causes its transparency, crystalline regions generally being more opaque than amorphous regions.

Due to their low capacity for biodegradation, the ubiquitous use of plastics in our society poses a serious problem for many environmentally-concerned individuals, and for good reason. Current plastic recycling programs are, to be frank, lacking, and this is majorly brought on by the economic limitations of recycling. Cultural attitudes towards sorting trash and recycled products also affect the efficacy of recycling programs. However, grass-roots activism and local- and national-level legislature are quickly changing opinions on the matter of plastic recycling. Knowing which plastics are recyclable (PETE, No.1, and HDPE, No. 2, only in many areas) will help to reduce the cost of sorting recyclables with a little effort, and public pressure for wider recycling programs may light a fire under companies to increase recycling, assuming the science exists. Research related to the synthesis of biodegradable polymers has picked up in recent years to produce products like polylactic acid (PLA, No. 7 (other)), but subsidies or funding is always welcome with science. If you're interested, these are things to talk to your local government representative about. 

So there you have it, a brief overview of the chemical and structural background of plastics (and a little bit on the side). Plastics are quite complicated and therefore impossible to talk about in depth through any medium shorter than a book, but if you want to hear more about specific aspects of polymers let me know in the comments and I’ll be happy to do so. Thanks!

Thoughts in Black Ink

The only foreign language that I claim to know is Japanese. I started studying Japanese in elementary school and took courses throughout middle and high school as well. Simple Japanese books, everyday conversations and Japanese YouTubers are fine for the most part, but vocabulary is still a problem for me. While at work the other day, I decided to practice some new terms I read on a blog post.

Fig. 1: Vocabulary practice (orig.)

Papers covered in words like this are scattered all over my room. Sometimes the need to write just gets to you, you know? Staring at the scribbled words, I suddenly thought, what is this stuff I’m writing with anyways? 

Ignoring the fancy colors, black pen ink is a relatively simple composition made of carbon black suspended in drying oils, alcohols or petroleum products [1]. Carbon black is carbon powder obtained by burning organic matter. This type of black ink has been around for thousands of years, and I use another form of the same stuff while doing Japanese calligraphy. East Asian calligraphy ink is traditionally made of pine soot (carbon black) mixed with bindings and herbs. This page provides a more in-depth description of how sumi, or a Japanese ink stick, is made.

Fig. 2: Carbon black sample molecular structure (Bruno Glaser)

So why is carbon black... black? Writer Maggie Koerth-Baker does a good job of describing this. In organic chemistry, pi-conjugated systems, or systems where electrons of sp² hybridized atoms are delocalized in combined p-orbitals, can exhibit a wide range of light absorption and emission properties. This is because of the many possible bonding and antibonding p-orbital orientations within the conjugated system.

Fig. 3: Molecular orbital states for benzene (Michigan State University)

When we talked about why excited metals emit colored light back in The Dazzling Chemistry of Fireworks, we mentioned that the Fermi level of metals is located within an electronic band, meaning that electron transitions between the highest occupied energy level and other higher energy electron states are possible over a range of values. The many available higher energy electron states are not unlike the many possible organizations of bonding and antibonding orbitals in pi-conjugated systems. An incident photon on a pi-conjugated system can upset the shared p-orbital system into occupying one of the possible antibonding arrangements, later to reemit the light energy at lower, sometimes non-visible spectrum, wavelengths. Pi-conjugated systems that include more atoms result in more complex molecular orbital states. And when conjugated units of varied length exist together in a material, then on the whole even more electronic states are possible! All of these electron transitions cooperate to make the familiar black ink of pens (graphite pencils too, just think about it).

If you enjoyed this post and those I've written before, share your thoughts in the comments to let me know!

A Quick Coffee Break

I know that I promised an explanation of what I meant in the last post by truly sustainable energy, and I still owe you guys that. But I wanted to take a quick break from environmental talk to discuss something of great importance to me: coffee. Everyday on the way to work, I stop by Dunkin’ Donuts to pick up a small iced coffee dark roast with cream and sugar. I’m there frequently enough that the employees have begun to reckon a pattern in my order (which basically doesn’t change). Some people aren’t coffee drinkers at all, and neither was I until I started college. The class that broke me was MSE 220. Don’t get me wrong, it was one of the best classes I’ve ever taken. It’s just that a dark, warm classroom was not conducive to my concentration as much as my nodding off.

Fig. 1: The usual Dunkin' Donuts morning coffee (orig.)

So let’s back up this post with a bit of content: coffee’s main active ingredient, as I’m sure you know, is caffeine. This relatively small organic molecule is the most widely consumed psychoactive drug and makes an appearance in many foodstuffs, especially in beverages. As a drug with dopamine-producing properties, it can be a source of addiction, though the symptoms of withdrawal are much lighter than those of controlled substances. The caffeine content for coffee, tea and soda types can be found here if you’re interested.

Fig. 2: Caffeine and adenosine molecules (University of Texas at Austin)

Caffeine works by competitively binding with adenosine receptors on neurons and is therefore deemed a receptor antagonist of all adenosine receptor types (A1, A2A, A2B and A3) [1]. Adenosine is a central nervous system neuromodulator that binds to receptors on neurons, slowing neuronal activity, dilating blood vessels and causing sleepiness [2]. I’m not good at tracking signaling pathways, but information on the adenosine pathway can be found here. When caffeine binds to the adenosine receptor, adenosine can no longer bind to slow neuronal activity and sleepiness is defeated. The increased neuronal activity caused by caffeine also induces the pituitary gland to secrete adrenaline and institute a state of “fight or flight” activity, another way caffeine energizes the sleepy world round [3].

Besides caffeine, there is other chemistry going on in coffee as well. A morning coffee is a good source of antioxidants (good for reasons mentioned in A Bit on That Shampoo Vitamin) and has been identified as the number one source of antioxidants in America, followed by black tea [1]. Coffee also has a nice hearty flavor, especially with my dark roast coffee, that comes from caramelization and Maillard processes (discussed back in Party Science, Part 3: The Tasty Grub) as well as the subtle bitterness of caffeine. And there you have it, a small cup of coffee science.

I’m going to try posting more photos that I take myself, but I’m not particularly trained in photography and only have my phone camera for the moment. Regardless, let me know what you think of the photos and if you have any photography tips I’d love to hear them. Anything helps!

Party Science, Part 3: The Tasty Grub

If you haven't already, please check out Party Science, Part 1: The Beats and Party Science, Part 2: The Lights.

To me, a party isn’t a party unless there’s food involved. Cooking and eating food is something that we all participate in on a daily basis, and the best food is usually to be had at parties. Let’s continue with the final installment of Party Science, Part 3: the Tasty Grub.

The creation of good food is closely related to a number of chemical reactions that make plant matter easier to eat, degrade potential toxins and impart a level of yumminess. From molecular kinetics, we know that the kinetic energy of molecules is proportional to temperature by the following equation:

                       1. E=nCvT, Cv=4.179 J/g°C for water (Chemical Principles, Zumdahl)

Therefore, by increasing the temperature of a foodstuff during cooking, we are increasing the kinetic energy and average molecular translational/rotational speeds and vibrational frequency. The result: destruction! As kinetic energy overcomes the hydrogen bonding energy of proteins such as enzymes, they begin to unfold and denature, losing their conformation and functionality. A classic example of this process is the denaturation of runny raw egg white proteins to produce the rubbery cooked egg white more commonly eaten than the former (deviled eggs anyone?). The degradation of structural proteins also plays a role in softening meats like steak during cooking (this process can occur faster at lower temperatures if enzymes that degrade proteins, such as those in pineapples and papayas, are used in a marinade to lower the activation energy of protein degradation). With plants, heating can denature certain proteins or compounds that are toxic to humans, increasing edibility. Heat also encourages the hydrolysis of cellulose [1] and starches. We experience this process through the soft texture of a baked potato.

As I’m sure you know, cooking also adds flavor to raw foodstuffs through a number of processes. One such process is caramelization, wherein sucrose inverts to produce fructose and glucose molecules that then undergo various reaction pathways to produce volatile, colored and flavorful compounds [2]. This process is notable in flans and apple pies. Another is the Maillard reaction, wherein sugars react with amino acids to again undergo various reaction pathways to produce tasty molecules [3]. The Maillard reaction is best known through the browning of cooked meat.

Fig. 1: The Maillard Reaction (Lynne Swerhone)

So far what has been described are all processes that have been in play for thousands of years, but what can chemistry offer to change the ways we prepare food? Well, if you’ve ever warmed up some cheese dip, then you know of at least one. Microwave ovens use microwaves (unsurprisingly) to warm up food by introducing a fluctuating electric field component that a water molecule’s dipole continually attempts to reorient with [4]. Chemistry has also fostered advances in modern food art and molecular gastronomy. If you ever use fruit juice boba as an ice cream topping or in mixing drinks, those are made of fruit juice mixed with calcium salts and dropped in sodium alginate, a soluble cellulose salt derived from brown algae (Fig. 2). When the sodium ions are replaced by aqueous calcium ions, insoluble calcium alginate is generated to seal in the juice drop in a process called spherification.

Fig. 2: Sodium alginate spherification (Molecular Recipes)

Thermodynamics has also brought us freeze drying through knowledge of phase diagrams and water sublimation [4]. The product is various forms of fruit and vegetable snacks, a healthy substitute for traditional party chips.

In many ways, party food is made to impress. Science helps us explain our current cooking techniques, and a good knowledge of these can allow for improvements and new innovations to reinvent regular party foods. With the music playing, the party lights on and the food ready to be served, your party prep is done so invite your friends and enjoy!

Below I am posting a cool video on how to make mojito spheres using molecular gastronomy, so check it out! And please tell me your thoughts in the comments below.

Experiment: Extraction of Plant Pigment as Food Coloring

My favorite drink to buy during Wawa lunch runs is Vitamin Water. Besides the extra boost of vitamins to supplement my college diet, I like that they use natural plant dyes rather than synthetic ones. To stop the kindling of a debate about whether synthetic dyes are bad for consumers, I would like to state that I don’t believe synthetic and natural chemicals are different; as a chemistry student, I assert that synthetically produced chemicals, if synthesized and refined properly, are the same as ones obtained naturally (aside from possibly isotope content, but I don’t see why that should matter). The problem with synthetic dyes at the moment is that some cannot hold their ground against investigations related to carcinogenic or other deleterious health effects, whether related to the compounds themselves or to manufacturers’ procedures. As for plant dyes, most have been consumer tested by humans for thousands of years. What’s more, natural plant dyes often have antioxidant properties. The biological role of antioxidants is another controversial topic, but suffice it to say that reactive oxygen species (ROS) and other reactive species are produced within your body continuously through processes such as metabolism and have been linked to tissue damage and cancer generation at high levels. Therefore, consuming a normal amount (not a 1,000mg vitamin C tablet every hour) of antioxidants through food can’t hurt and may even have health benefits. The point of bringing up this topic is to introduce the first home experiment I am posting on this blog. I am going to demonstrate how to extract plant pigments for use as food coloring.

Materials:

• High ethanol content liquor (vodka)
• 40% (80 proof) vodka used
• Higher proof makes volume reduction easier due to lower boiling point of ethanol 
• Pyrex glass container for extraction
• Liquid measuring cup used
• Frying pan for water bath
• Plant matter
• Tested: canned beets, spinach, watermelon, blackberries
• Worked: canned beets, blackberries

Procedure:

• The frying pan was filled 3/4 way up with water, then heated over medium heat until small bubbles formed.
• Plant matter was added to the Pyrex container with enough vodka to cover it, then the container was placed into middle of the frying pan bath.
• The reaction was left for approx. 30 min (until the color of the vodka no longer appeared to be changing and alcohol could no longer be smelled).

Fig. 1: Coloring extraction setup

• The reaction mixture was transferred to a ceramic bowl, then the plant matter was removed before letting the colored solution cool to room temperature.

Fig. 2: Coloring concentration

• The ceramic bowl was covered and the coloring solution was set to concentrate overnight. The bowl was swirled occasionally to recollect dried dye along the waterline.

Results:
Of the tested plants, the canned beets and blackberries were the only two to work. Both produced a similar hue of purple-red coloring. When the blackberry coloring was used on cream cheese frosting, the result was a light purple-red pastel frosting with a slightly runnier textured due to inadequate dye concentration prior to use and to mixing (Fig. 3). Adding a teaspoon of the dye to a cup water imparted a moderate red coloring which soon thinned (Fig. 4). in both instances, no blackberry taste was conferred (same for beets).

Fig. 3: Blackberry colored cream cheese frosting

Fig. 4: Blackberry colored water

Explanations:
For setup considerations, Pyrex and ceramic containers were used to hold the dye solution as a precaution against possible dye discoloration due to reactions with the container. Low boiling water was used to roughly manage the reaction temperature while reducing the chance of degradation, due to heat in this instance. Coloring concentration was performed prior to testing as a precaution against changes in food texture due to the addition of large quantities of water. The concentrating bowl was covered to prevent dust from depositing in the coloring solution and to lessen the chances of dye degradation due to interaction with ambient light. Vodka was used for extraction rather than water to lower the external polarity relative to the plant material's internal environment. The result is a polarity gradient across the membrane of the plant cells that aided in the migration of relatively non-polar dye molecules outward from within the plant cells while trapping other more polar molecules, one such molecule type being sugars, that would confer flavor. In this way, the coloring produced by this method differs from the juice of the tested plants. Dye color consistency should be considered when using the blackberry coloring, as anthocyanin pigments respond to changes in pH with changes in color. Color degradation over time is another consideration, and coloring soon before consumption is recommended (when added to water, the coloring soon reduced in intensity, an effect which may be reduced or enhanced by the contents of what is being colored) The produced colorings will contain ethanol at low concentrations, a consideration more than a concern. 

I was only able to produce purple-red coloring, but it is likely that other untested plant materials will be able to produce differing colors. I will be leaving which plants can color be extracted from in this method as an open question, so if you find any others please let me know in the comments!

How Soap Helps Us Clean

Ever wonder why it is that we use soap to clean our cars, dishes, bodies and hands? Aside from dyes, perfumes and other additives, soap contains molecules called surfactants. Surfactants are complex molecules that have hydrophobic "tail" regions consisting of long carbon chains and hydrophilic "head" regions that are charged or polar. Some of the oldest soaps were made by heating water washed through wood ash (called caustic soda, lye, or sodium hydroxide) with a fat source [1]. Fat sources can be triglycerides from animal fat, fatty acids from plants or other sources of similar molecules often possessing a carboxylic acid (hence the term "fatty acid") or fatty acid-derived ester group as in triglycerides. The chemical reaction that results is called "saponification" and involves the cleavage of triglyceride fatty acids by hydroxide ions forming glycerol and neutralization of the fatty acids to form salts of the fatty acids.

Fig. 1: Saponification mechanism for fatty acid-derived esters in triglycerides (University of Malta)

An example of the type of fatty acid salt that results from saponification is sodium oleate;

Fig. 2: Sodium oleate (Exporters India)

This surfactant molecule is formed by reacting sodium hydroxide with oleic acid, better known as olive oil. So how do these surfactants help to clean dishes? Let’s think about what types of foods are the worst to clean after cooking dinner. Sugary syrups from cranberry sauce, jams and the like are a breeze to clean; just rinse the dishes and bam, they’re clean. This is because sugars are water soluble. The oily pan used to fry meat, however, is a mess and gives your hands that slick feeling everybody hates. Oil is hydrophobic and will likely stick to your pan better than it does to the water running over it. Here is where soap helps. Above a critical concentration, surfactants tend to form clumps in water called "micelles" so that all of the hydrophobic tails are collected inward (a bilayered micelle is a lysosome, and a lysosome with its hydrophobic tails pointed outward containing a water layer of varying thickness is a bubble).

Fig. 3: Surfactant organization forms in water (Wikipedia)

Exactly at what concentration these micelles form is dictated by thermodynamics in balancing the loss of entropy from organizing the surfactant molecules against the higher energy of associating water and the hydrophobic tail regions [3]. When soap is applied to the oily pan surface, the hydrophobic tails embed in the oil and form it into small droplets. The oil is then escorted by the hydrophilic head regions into the surrounding water and down the drain when rinsed. It is this ability to make hydrophobic substances pseudo-hydrophilic that makes soap so useful to us. What about washing cars and our bodies. While the circumstances are radically different and accordingly warrant different surfactants, the mechanism is the same. Soap helps to escort away hydrophilic bits in dirt, grime and bird poop on cars and dead cells and human oils on our bodies, helping to keep things in line with our modern sense of cleanliness.

So there you have it, a summary of how we utilize soap. If you guys have any topics you would like to hear about or this article tickled your fancy, leave a comment so I can hear your thoughts. 

The Dazzling Chemistry of Fireworks

Yesterday was the Fourth of July, and millions of people all over America gathered in parks and along waterways to witness one of the most dazzling examples of ancient science; fireworks. The invention of gunpowder in China ca. 600-900 CE resulted in the creation of the first fireworks, later buffed up to the colorful sky-flowers we know today by Italian fireworks makers in the 1830s [1]. While waiting for a fireworks display at the Philadelphia Museum of Art, I found myself wondering how is it that we humans have come to create this technology. The first step was to devise a method of controlling highly exothermic and expansive (due to gas formation) chemical reactions and initiate them on purpose through the use of chemical oxidizers (originally saltpeter, KNO3) that contribute oxygen to combustion reactions, allowing them to burn in containers without oxygen flow or even in vacuums. But the role of gunpowder in history has had many uses beyond fireworks and isn’t what makes this specific variety of chemical explosions so addicting. What gives fireworks their characteristic hues are the metal ions that exist along with the crafted gunpowder in fireworks shells. Italian fireworks makers discovered that the use of KClO3 rather than saltpeter could increase the temperature of the combustion reaction, allowing for the light-emitting potential of metal ions to be unleashed [2]. When calculating the standard enthalpy of reaction for the following decompositions;

1.     2KNO3 --> K2O + N2 + 2.5O2

2.     2KClO3 --> 2KCl + 3O2

it can be observed that the decomposition of KClO3 is more exothermic than that of KNO3 (625 kJ/mol for KNO3 and -89.6 kJ/mol for KClO3 based on standard enthalpies of formation found on Wikipedia), the former also generating 0.5 more moles of O2 gas than the latter. The extra oxygen gas contributes to the exothermic nature of the combustion through the formation of CO2 and SO2 gas (-393.5 kJ/mol for CO2 and -296.81 kJ/mol for SO2 based on Wikipedia values), the same source of energy from which coal power plants operate, according to the following equations:

3.     C + O2 --> CO2

4.     S + O2 --> SO2

The color that a given metal salt produces when heated is characteristic of the metal element and can be calculated based on the following equations [3,4];

5.     E=hv 

6.     c=lv (v=fl modified for light)

7.     E=hc/l (from equations 5. and 6.)

8.     E=-Rhc(1/(nf)^2-1/(ni)^2) (Rydberg Formula*)

*note: UC Davis source seems to consolidate the Rydberg Formula hc term into the Rydberg constant, as evidenced by their subsequent derivation eliminating the hc term against the value of R.

Fig. 1: Sodium electron orbital energy diagram (Whitman College)

From the above electron orbital energy diagram for sodium, it can be seen that the transition between the highest occupied molecular orbital (HOMO), the 3s orbital, and the lowest unoccupied molecular orbitals (LUMO), the 3p set, corresponds to an emission of light in the 589nm wavelength region, or yellow light. This fact is experimentally verified since the yellow color of fireworks is often produced by sodium salts. It is in this fashion that the colors each metal element produces can be understood. So why metals? Well, the emission of light in various visible colors is reliant on electron energy state transitions as we just discussed, and electron band structure properties for metals tell us that the Fermi level, or highest occupied energy level (HOMO energy level), lies in the middle of an electron band in metals, meaning that there are higher electron energy levels to which metal electrons may be excited [5]. So metals are used simply because in our universe these are the elements that are capable of light-producing electron transitions.

Of course other factors must go into fireworks to achieve such controlled chemical acrobatics as producing tailed explosions or glittery rain, but with bang and color you have the basic makings of this recreational technology that is also a marvel of modern chemistry. 

I plan to do experiments inspired by daily events or questions that arise, so comment if this post has brought up any topics you would like to hear more about or want to see experiments on. Thanks!