This article was written by Abigail Jeorrett.
A stuffy classroom with a faded poster of the periodic table, wooden benches that bear the scars of misjudged experiments and cupboards filled with a multitude of equipment: beakers, flasks, pipettes, and of course, the trusty Bunsen burner. This is my memory of high school chemistry, and it is where my interest in the subject was sparked. For many though, it was difficult to connect the prescriptive experiments and dry textbooks of their school days with the world beyond. I am an unashamed chemistry nerd, but after years spent in a lab, there is a lot that still surprises me about the often, enigmatic life of chemicals.
If you think about your daily routine, from having a morning coffee to practising your samurai sword skills, you are exposed to hundreds of chemicals. The word “chemical” often conjures up images of mysterious glass bottles containing brightly coloured liquids and bubbling beakers of strong-smelling concoctions. A chemical is defined as a basic substance. Chemistry is the study of these substances and how they react and combine. Unlike the days of old, when one of the main objectives of an early form of chemistry (alchemy) was to turn lead into gold, today it is studied to understand the properties of chemicals. This is done so we can use them safely to our advantage, and to have a little fun.
Morning Beverage
Let’s start with the most popular psychoactive drugs that humans consume: coffee. The caffeine in coffee is a chemical impostor. Caffeine has a similar shape to a naturally occurring chemical called adenosine. When adenosine binds to receptors in your brain, your neurons slow down and your body prepares for sleep. Caffeine takes the place of adenosine, which results in an increase in neuronal activity. As your brain activity increases, your body responds by releasing the hormone adrenaline. A “fight or flight” response is triggered that increases your heart rate and prepares your body to face a real or perceived threat. The effect of adrenaline is the reason coffee can make you feel edgy but up for a challenge.
If you are not a fan of the effects of caffeine, or you are preparing for an early sleep, there is always decaf. The process of extracting caffeine from coffee is surprisingly simple. Two chemicals can be used, methylene chloride or ethyl acetate. Methylene chloride is a chemical with which you should not tango. It is typically found in paint stripper and mild exposure can lead to dizziness and nausea. Heavy exposure can lead to death. Ethyl acetate, on the other hand, naturally occurs in fruits and smells like pear drops. One of these chemicals is washed over green, pre-roast coffee beans and caffeine transfers from the beans to the chemical wash. The wash is then evaporated, and the beans given a much-needed rinse and steam treatment, leaving them caffeine-free and ready for roasting.
Bubbles, Bubbles Everywhere
Whether it’s a morning shower or an evening soak in the bath, bubbles are a pleasing part of our daily lives. They are created using two simple ingredients: soap and water. Soap is a chemical with a dual personality: one end of each molecule is happy being close to water (hydrophilic) and one end is happy being far away from water (hydrophobic). A single molecule of soap looks a bit like a tadpole, with a hydrophilic head and a hydrophobic tail. When air is introduced into a solution of soap, bubbles with a three-layered surface structure are created. The inner and outer layers of the bubble’s surface both consist of soap. In the inner layer, the hydrophobic tails of the soap all point inwards and in the outer layer, they all point outwards. Sandwiched between the soap molecules is a layer of water. All the heads of the soap molecules point towards the water layer. Bubbles form spheres as this results in the lowest surface tension (i.e. the lowest surface to volume ratio).
The iridescent surface of bubbles is due to the interaction of light with the two layers of soap. Light can be thought of as waves, like ocean waves but made of energy. White light consists of all the colours of the rainbow and each colour has its own wavelength, the distance between consecutive waves. When light interacts with a bubble, it can either be reflected by the inner or outer layer of soap. Light travels slightly further if it is reflected from the inner surface. When the light waves recombine as they leave the bubble, they can interfere constructively or destructively. If the light interferes constructively, the waves add together to create colours and the wavelength of light depends on the thickness of the water layer. If the light waves interfere destructively, the light is cancelled out. The water layer varies in thickness across the surface of the bubble, so all the colours of the rainbow can be seen to shimmer as the bubble wobbles through the air.
Fade to White
If you are anything like me, you may end up spilling your lunch in your lap, especially on days when morning coffee has not been consumed. Fortunately, there are many products at our disposal to clean up after our clumsiness. Bleach is a chemical that contains sodium hypochlorite, a fancy name for a substance that contains the elements sodium, chlorine and oxygen. These elements form a single bond, or connection, between each other. Single bonds are the most common and easily formed, but coloured substances make the extra effort to get to know their atomic neighbours a little better and form double bonds. It is the difference between doing a spin-your-partner manoeuvre during a frantic strip the willow whilst holding both your partner’s hands, instead of the riskier one-handed strategy. Double hand holding and double bonds are more stable. I still have the scars to support this statement.
Substances that form double bonds can interact with light in fun ways. They can absorb certain wavelengths, or colours, of light and reflect others giving them a distinctive appearance, in the case of stains, usually an unsightly mess. Bleach is rich in oxygen which results in oxidation of the stain. Oxidation breaks down double bonds and prevents them from absorbing light. So, bleach does not really get rid of a stain, but the stain will fade to white when exposed to this destructive chemical and become less visible.
S’mores & More
Usually an activity reserved for a cold evening around a campfire, making s’mores is a joy for many and involves one of my favourite chemical reactions, combustion. Fire has been a constant source of fascination to humans for thousands of years, but at its most basic, it requires only three things: oxygen, fuel, and heat. When building a campfire, this means collecting wood for fuel, a match for heat, and a ready supply of oxygen-containing air. Marshmallows are fluffy delights that consist mainly of sugar and caramelise when toasted. Caramelisation is perhaps one of the most delicious series of chemical reactions but only occurs at high temperatures, such as those reached by a campfire. Sugars are broken down then recombine to make the familiar “nutty” flavours and golden-brown colours associated with caramelised food. If you get distracted, your marshmallow may end up pyrolyzed, otherwise known as burnt, which produces bitter chemical products.
Cold evenings are not just for campfires and s’mores. You may also brave the outdoors on one night in November to witness a more exciting relative of combustion, explosion. These two reactions are essentially the same, except explosions occur much faster. When you see a firework speeding into the night sky, potassium nitrate is at work. It is the main ingredient of gunpowder and forms the “charge” of a firework. Potassium nitrate is rich in oxygen, charcoal is added to provide fuel, and heat can be provided by a brave human with a lighter or a remotely operated electrical charge. The bursts of colour are created by metal salts which are substances containing a metal and a non-metal, bound together by the attraction between positive and negative charges. The metals used in fireworks determine the colour from red-producing strontium to blue‑producing copper. Purple requires the combination of strontium and copper salts, which can be a bit of a chemical challenge, so be sure to make your most excited oohs and ahhs the next time you see a purple firework bursting in the night sky.
Fullmetal Alchemist
Metals form most of the elements in the periodic table and they have many surprising properties. Some are hard and relatively unreactive like tungsten, while others are soft and react violently to moisture in the air like sodium. Some melt in the palm of your hand like gallium, while others are already liquid at room temperature like mercury. Some are even a gas at room temperature like Copernicium. The most abundant metal on Earth is iron. I know what you’re thinking, iron is not that interesting, but stay with me. When combined with carbon, iron becomes steel, and steel can be used to make samurai swords. These painstakingly crafted weapons have long been viewed as the pinnacle of sword smithery. The secret to their strength and enduring appeal lies in the technique used to create the blade and the resulting chemical structure of the metal.
To make the blade, steel is first folded repeatedly to incorporate carbon, remove air bubbles and draw out impurities. A soft, low‑carbon steel core is then combined with a hard, high‑carbon steel outer shell. After these two components are forged together, the back edge of the blade is coated in a mixture of clay and charcoal to provide insulation during the final heating stage. Cooling, or “quenching”, results in a difference in the chemical structure of each side of the blade due to the insulating coating. It is this stage that creates the characteristic curved blade of the katana. The sword smith’s knowledge of the chemical properties of steel, and their skills as a craftsman, results in a formidable weapon that has been revered for thousands of years.
References & Further Reading
dictionary.cambridge.org/dictionary/english/chemical [Accessed: 6th May 2020]
dictionary.cambridge.org/dictionary/english/chemistry [Accessed: 6th May 2020]
Cappelletti S., Daria P., Sani G. & Aromatario M. (2015) ‘Caffeine: Cognitive and Physical Performance Enhancer or Psychoactive Drug?’, Current Neuropharmacology, 13(1): pp. 71-88. https://doi.org/10.2174/1570159X13666141210215655
Ribeiro J. A. & Sebastio A. M. (2010) ‘Caffeine and Adenosine’, Journal of Alzheimer’s Disease, 20(1): pp. S3-S15. https://doi.org/10.3233/JAD-2010-1379
Dowling S. (2018) ‘How do you decaffeinate coffee?’. Available at: www.bbc.com/future/article/20180917-how-do-you-decaffeinate-coffee [Accessed: 6th May 2020]
‘Toxicological Profile for Methylene Chloride’, U.S. Department of Health and Human Services, Public Health Service, Agency for Toxic Substances and Disease Registry (2010). Available at: www.atsdr.cdc.gov/toxprofiles/tp14.pdf [Accessed: 6th May 2020]
Nakama Y. (2017) ‘Surfactants’, Cosmetic Science and Technology: Theoretical Principles and Applications, Elsevier Inc., pp. 231-44. https://doi.org/10.1016/B978-0-12-802005-0.00015-X
Cohen C., Texier B. D., Reyssat E. & Snoeijer J. H. et al (2017) ‘On the shape of giant soap bubbles’, PNAS, 114(10): pp. 2515-19. https://doi.org/10.1073/pnas.1616904114
Hipschman R. (1995) ‘Bubble Colours’. Available at: https://www.exploratorium.edu/ronh/bubbles/bubble_colors.html [Accessed: 6th May 2020]
Holst G. (1954) ‘The Chemistry of Bleaching and Oxidizing Agent’, Chemical Reviews, 54(1): pp. 169-94. https://doi.org/10.1021/cr60167a005
Compound Interest (2013) ‘The Chemistry of Fireworks’. Available at: www.compoundchem.com/2013/12/30/the-chemistry-of-fireworks/ [Accessed: 6th May 2020]
Russell M. R. (2000) ‘The Chemistry of Fireworks’, Cambridge, Royal Society of Chemistry.
Inoue T. (1997) ‘The Japanese Sword: The Material, Manufacturing and Computer Simulation of Quenching Process’, Materials Science Research International, 3(4): pp. 193-203. https://doi.org/10.2472/jsms.46.12Appendix_193