Today’s graphic explores the chemistry of Levi’s® famous blue jeans. It’ll show you why they’re blue, and how the dye is made; why the blue colour survives so well in the wash; and what’s special about the denim cotton weave that makes your Levi’s® jeans so strong.
Indican is a colourless, water-soluble compound extracted from leaves of the Indigofera species. Indican is a dextrose molecule conjugated to an indoxyl group by a glycosidic ether (C–O–C) bond.
The indican is hydrolysed at high pH, which separates the dextrose from the indoxyl group. The resulting indoxyl compound is whisked to aerate it, which causes the indoxyl molecules to oxidise and dimerise into indigotin, which is the famous blue dye used in Levi’s® jeans.
However, the indigotin blue dye isn’t soluble in water, and must be changed chemically before the jeans are dyed. Indigotin is subjected to high pH again, which reduces the indigotin, forming leuco-indigotin (also known as indigo white dye), which is, despite the name, pale yellow in colour.
Jeans are steeped in this water-soluble “indigo white dye”, which is still pale yellow at this stage! However, as soon as the jeans are removed from the vat of dye, the leuco-indigotin oxidises back into indigotin, which is blue in colour. The oxidised form (indigo blue) is insoluble in water, which helps the colour stick to the jeans despite being washed hundreds of times.
Denim is a traditional way of weaving cotton into a thick, sturdy material. Cotton is predominantly cellulose, a strong polymer of beta-D-glucose monomer units. Several thousand glucose monomers are present in each polymer chain. Polar hydroxyl groups form hydrogen bonds with hydroxyl groups on adjacent chains to form strong microfibrils, which the cotton plant then meshes into a strong poly- saccharide matrix. This matrix, and the denim weave, give high strength and durability to your Levi’s® jeans. ●
Many people are openly addicted to coffee. In northern Europe, home of the world’s greatest coffee drinkers, annual coffee bean consumption hovers around 9 kg per capita, which equates to 400 mg of caffeine per person per day (this is a highly addictive, highly stimulating dose). In North America, coffee bean consumption is much lower at 4.2 kg per capita per year, which equates to 185 mg of caffeine per person per day. However, this is still a highly addictive dose.
Caffeine (around 225 mg in the beverage shown above) causes short, sharp increases in your blood pressure. It makes you feel alert, but jittery in large doses. Caffeine stimulates nerves by counteracting adenosine, which is a nerve activity suppressant. The brain develops a tolerance to caffeine intake after a few weeks, which can cause some people to take increasingly large doses—sometimes exceeding the ~300 mg per day limit recommended by many doctors. That said, smaller doses are believed to provide some protection against Parkinson’s Disease in the long term.
Milk, a butterfat emulsion, gives the coffee its light colour and pleasant mouthfeel. Vanilla syrup adds an interesting flavour and aroma, and consists of glucose syrup and vanillin, an artificial flavour compound modelled on the main aroma compound in real vanilla beans.
The most amazing aspect of the product shown is the polypropylene cup. Starbucks® sells these reusable cups for just $1 in its United States stores, which is part of an attempt to serve 5% of all its beverages in reusable containers by 2015. In addition to giving you a 10-cent discount for bringing your own cup, and selling these reusable cups ridiculously cheaply, Starbucks® makes these cups from a fully recyclable plastic that’s completely inert at boiling-hot temperatures (100°C). This ensures that absolutely nothing from the cup leeches into your piping hot drink before you drink it. ●
Compete with thousands of other students from around the world by taking part in this epic crystal-growing experiment aimed at students aged 7-16, hosted by the Royal Society of Chemistry (RSC).
The aim of the Global Experiemnt is to find the exact conditions that allow you to grow the biggest, most impressive crystals of alum, epsom salts, potassium nitrate, table salt and sucrose. Students do the entire process themselves, then post their pictures and data onto the RSC’s global, interactive results map. Here’s their instructional video:
Through getting your students involved in this year’s Global Experiment, you’ll be teaching them about dissolving, saturation and crystal growth. You’ll be engaging them in a fun, interactive science project they can easily continue at home. The RSC has even provided instruction packs, lesson plans and an instructional video to make the planning process as easy as possible for teachers.
It’s free to take part, and no specialist equipment is required. It can be done entirely using a few cheap things purchased from a local store. It can be done at home, at school or at an after-school science club.
Cherries are extremely sweet, and are unusual in that they contain more glucose (52%) than fructose (42%). Their bright red colour comes from the carotenes and capsanthin (the E160 colourings) that are present in high quantities throughout the fruit.
Cherry flavour comes from a huge collection of aroma compounds produced naturally by the cherry. To make all of these compounds in the lab, then mix them together in the correct proportions would be ridiculously time-consuming and expensive.
When making artificial cherry flavourings, only the first two compounds are usually added: (Z)-3-hexenol and 2-heptanone. Artificial cherry flavouring thus tastes absolutely nothing like real cherries: it lacks most of the ingredients that give real cherries their delicious flavour.
It’s quite a different story with oranges and lemons, though. Most of the flavour of oranges and lemons comes from (+)-limonene and (-)-limonene, which, by themselves, smell like orange and lemon, respectively.
The video made me feel sorry for LEGO®. It also reminded me that LEGO® is made from oil-based products (even though they’re trying to find a sustainable alternative), and it inspired me to make this infographic: the Chemistry of everyone’s favourite building block.
LEGO® is made from ABS (acrylonitrile butadiene styrene), a thermoplastic polymer comprised of three monomers. The first monomer, acrylonitrile, gives the bricks strength. The second, 1,3-butadiene, gives them resilience (i.e. stops them from snapping so easily) and the third, styrene, gives them a shiny, hard surface. These three ingredients are mixed with colorants then polymerised (hardened) with the help of an initiator called potassium peroxydisulphate. LEGO® buys pre-made ABS granules and injects them into brick shapes on a massive scale.
LEGO® make 20 billion bricks each year (that’s 35,000 bricks a minute) and according to the Guinness Book of World Records, they produce more plastic tyres than anyone else. Personally, I think that’s a remarkable feat. It’s engineering genius.
In a statement, LEGO® said: “We firmly believe that this matter must be handled between Shell and Greenpeace. We are saddened when the LEGO brand is used as a tool in any dispute between organisations. We will continue to… deliver creative and inspiring LEGO play experiences to children all over the world.” •
Inspired by the recent Peach infographic, I set out to find the least natural fruit in existence, and decided it was probably the modern watermelon. Take a look below: which one would you rather eat?
The watermelon, delicious as it is, has increased from 50 mm to 660 mm in diameter, which represents a 1680-fold increase in volume. While ancient “wild watermelons” weighed no more than 80 grams, modern watermelons can range from 2 kg to 8 kg in the supermarket, while the Guiness World Record for the heaviest watermelon recorded exceeded 121 kilograms in the year 2000. Thousands of years of human-induced evolution have worked miracles on these fruits. Let’s not forget that they’re completely artificial.
The most famous example of artificial selection is of course the selective breeding of the feeble teosinte plant into juicy, delicious, North American sweetcorn.
In 9000 years, sweetcorn has become 1000 times larger, 3.5 times sweeter, much easier to peel and much easier to grow than its wild ancestor. It no longer resembles the original teosinte plant at all. Around half of this artificial selection happened since the fifteenth century, when European settlers placed new selection pressures on the crop to suit their exotic taste buds.
That’s all for now… More exciting infographics coming soon. Enjoy! 😉
Why is Gold yellow? Special relativity causes length contractions and time dilations in objects that travel at speeds approaching the speed of light. The valence electrons of large atoms such as gold have such high energies that their speeds actually approach the speed of light—and the relativistic effects on those electrons can become quite large.
Special relativity changes the energy levels of the 5d orbital in a gold atom so that the energy difference between 5d and 6s orbitals equals the energy of a ‘blue’ photon. Gold thus absorbs blue light when electrons are elevated from the 5d to the 6s orbitals, while other metals do not. These special relativistic changes to the energy levels of atomic orbitals are slightly different for each element.
Relativistic contractions on gold’s valence electrons (the 6s subshell) pull the 6s electron very close to the nucleus. Being closer to the nucleus makes the 6s electron less accessible to any potential reactants. Special relativity is not only the reason for gold’s yellow colour but also for its very low reactivity! ●
This artificial vs natural foods phenomenon has grown somewhat since the All-Natural Banana.
This infographic explores the differences between the natural, “wild peach” and its modern, artificial relative. It explores how the ancient Chinese developed a small, wild fruit (that tasted like a lentil) into the juicy, delicious peaches that we eat today.
This image also pays homage to the thousands of years of toil that farmers put into developing the Peach regardless of whether they were aware of it consciously or not.
After the wild peach was domesticated in 4000 B.C., farmers selected seeds from the tastiest fruits for re-planting. They tended to the trees for thousands of years, and the fruits became bigger and juicier with each generation. After 6000 years of artificial selection, the resulting Peach was 16 times larger, 27% juicier and 4% sweeter than its wild cousin, and had massive increases in nutrients essential for human survival as well.
If you’re in high school, you should spend about two thirds of each day studying for six days each week for several months before your important exams. But apart from doing the required homework, what else should you be doing in that time?
Answer: Just 2 things.
(1) Make great notes.
Make them, re-make them and then make them again. Make them clearer and more beautiful every time. Organise them according to the official study design (or “syllabus”) for your course. Put your notes on the wall of your bedroom or study. Take some of them down temporarily and see if you can recall them by heart.
You can buy books of theory notes online, but the process of making your own notes is when most of the theory learning actually takes place. Use those purchased books for inspiration only. It’s okay to use a computer to make notes, but do at least one hand-written version as well. Become a pro at hand-writing explanations and sketching diagrams with a pen. This experience will save you time in the exam.
(2) Do lots of practice questions.
Get practice questions from as many sources as you can. Use real past papers, use past-paper-style questions from companies, and if you need more, do questions from the textbooks your school isn’t using. Complete these questions first without answers, then refer to your theory notes if you get stuck. When done (or if completely stuck), check the answer key or send an email to your teacher. Do all of this in one study session.
That’s almost all there is to it! I’ll post more about each of these two instructions in the next two weeks. Making great notes and doing lots of practice questions are the two most important parts of exam revision.