Colourful Chemistry: Chemistry of UNIVERSAL INDICATOR

Chemistry of UNIVERSAL INDICATOR jameskennedymonash
jameskennedymonash.wordpress.com

By definition, an indicator is a substance that changes colour in different pH environments. Universal indicator is a brown-coloured solution—containing a mixture of indicators—that can be added to any substance to determine its pH. Like all indicators, universal indicator changes colour in different pH environments. At low pH, it appears red, and at high pH, it appears blue or violet. At neutral pH, it appears green. Universal indicator can form a continuous spectrum of colours that give an approximate reading of the concentration of protons in a sample.

Water and propan-1-ol are used as solvents. They are both polar and dissolve all the other ingredients in the solution. Sodium hydroxide (NaOH) is an alkaline solution that adjusts the pH of the universal indicator to ensure that each colour is shown at the correct pH value. It is necessary to add NaOH to the universal indicator because some of the indicator compounds (e.g. methyl red) are acidic themselves, which would affect the colour of the other indicators present. NaOH is added to neutralise the solution.

Methyl red is red at pH <5 and yellow at pH >5. It provides orange and red hues to the universal indicator solution at low pH. The end point of an indicator compound is defined as the pH at which it changes colour. The end point of methyl red, therefore, is somewhere around pH 5.

Bromothymol blue is blue at pH >6 and yellow at pH <6. It gives blue and indigo hues at high pH. Its end point is therefore around pH 6.

Thymol blue has two end points: it is red below pH <2, blue at pH >8 and yellow in the middle. Thymol blue allows universal indicator to differentiate low and very low pH by providing another red hue below pH 2. Thymol blue is yellow at pH 7, which, when combined with bromothymol blue (which is blue at pH 7), give a green colour.

Finally, phenolphthalein gives universal indicator a deep violet colour at very high pH.

This 2-miunte BBC video is a great introduction to universal indicator:

Happy Mid-Autumn Festival! New infographic: Chemistry of MOON CAKES

Chemistry of MOON CAKES infographic jameskennedymonash
jameskennedymonash.wordpress.com

Mid-Autumn Festival (中秋节) is a traditional Chinese festival celebrated on the 15th day of the 8th lunar month each year (a full moon night in September). It started as an agricultural tradition (like harvest festival in western cultures) around 1000 BC in the Zhou Dynasty, and was formally acknowledged as a festival during the Northern Song Dynasty (between 960 and 1279 AD).

Today, Mid-Autumn Festival is celebrated with moon cakes, family reunions and three days off work. Moon cakes are circular to represent the full moon that always occurs on the Mid-Autumn Festival. Watch the video below to learn about the story behind the festival:

Moon cakes consist of crust, filling and an egg wash. The crust is made from flour, the polysaccharides in which bind together at oven temperatures to form a strong, intricate network (also including proteins) that allows the moon cake to keep its all-important circular shape.

The crust also contains invert sugar syrup, which is chemically similar to both honey and golden syrup. Invert sugar syrup is made by hydrolysing sucrose into its constituent monomers, glucose and fructose. The result is a sweeter-tasting, gooey liquid that doesn’t crystallise during cooking. This gives the moon cake a smooth mouthfeel.

Peanut oil (a blend of mostly monounsaturated triglycerides) is added to the crust for two reasons. First, it is a non-volatile liquid at room temperature, which prevents the moon cake from drying out. Second, the peanut oil molecules disrupt the protein matrix in the crust and give it an even smoother texture (not a doughy texture).

Maillard reactions are caramelisation reactions involving the removal of two hydrogen atoms from a sugar aldehyde or ketone. The resulting compounds are yellow/brown in colour because they contain carbon-carbon double bonds (C=C), which absorb violet and UV light (λmax ≈ 190 nm). The moon cake is usually also given an egg wash, which provides extra protein necessary for Maillard reactions to occur. More egg wash will provide a deeper brown colour to the dough.

Alkaline water (枧水) is a common ingredient in Guangdong-style cuisine. Chemically, it’s a ~0.020 molar solution of potassium carbonate and can be considered as the ‘opposite of vinegar’. It raises the pH in the moon cake, which accelerates the Maillard reaction, which is favoured by alkaline conditions. Alkaline water thus makes the crust more brown!

Finally, the fillings can be very diverse. Lotus seed with salted duck egg yolks is a common filling, but “five kernels”, red bean and green tea (with beans) are also quite popular. Lotus seed filling, for example, is made by soaking dried lotus seeds in alkaline water, pulverising and adding sugar. The resulting paste is then cooked with more oil and sugar before being used to fill a moon cake. ●

Full “Ingredients” Poster Set Just $99 with Free World Shipping!

From today, all 12 Ingredients of an All-Natural Banana (and other Fruits) posters are available for just $99 with free world shipping by clicking the image below.

Ingredients of an All-Natural Banana and other fruits set $99

They’ve been featured on dozens of news websites and magazines and received over 2 million views in total this year. They started as an educational ‘hook’ for the classroom (specifically to introduce organic chemistry), but went viral online and sparked articles from all sides of the “is natural always best?” debate.

From today, get the entire original 12-poster set on sturdy 300 gsm card stock for just $99 with free world shipping by clicking the button above. (Usual selling price is $10 each plus postage).

VCE Chemistry curriculum gets tougher, more interesting in 2016!

Originally posted at VCEasy.org

VCAA has just released its proposed draft VCE Chemistry study design for 2016-2019.

Major changes are in store for future VCE Chemistry students.

First, the Key Knowledge points have been restructured into subheadings. These subheadings represent 37 enquiry-based “topics” across Years 11 & 12 that each take 1 or 2 weeks to teach. This makes planning the curriculum a little easier, and makes the course structure a little more visible for students.

Second, the school-assessed coursework tasks are more specific and more exciting. units 1-4 include extended investigations (like the EPIs done in Physics). Students produce posters, reports or do presentations at the end of each unit. Some examples are shown below (there are more choices available in the full Study Design):

“the properties of a chemical or material that make it useful with specific reference to its structure and bonding, analyse its life cycle and evaluate the impact of its production and use on resources and the environment.” (Unit 1);

“a quantitative laboratory investigation related to the quality of water.” (Unit 2);

“analysis and evaluation of two or more media articles related to energy options.” (Unit 3);

“response to an issue related to food and diet.” (Unit 4)

Third, history of the atom and history of the periodic table have been taken out of the curriculum and replaced with something far more exciting: the Big Bang and how the universe started. The first three chapters of the text book will have to be re-written! Many other (minor) course changes have also been made.

Finally, the entire Chemistry course is much more detailed. Organic molecules now include alkynes and are studied up to C10, for example. The only problem is that it’ll be more difficult to squeeze all the topics into the same amount of time. Students and teachers will probably be working a little harder as of 2016…

What do you think of the new 2016-2019 study design? Read it and give your feedback on VCAA’s Chemistry page (click here).

Links

Draft Study Design (pdf – 655.45kb)

Summary of proposed changes to the Study Design (doc – 423kb)

How do headphones work? New infographic: Chemistry of BEATS®

Chemistry of BEATS® Headphones jameskennedymonash.wordpress.com
jameskennedymonash.wordpress.com

If you’ve ever tried Beats® headphones, you’ll have felt the rich, powerful baselines they give you without overwhelming the rest of the music. Beats® and its music streaming service, BeatsMusic, have become so popular so fast that they now recently acquired by Apple for a whopping $3 billion, making co-founder Dr Dre the most financially successful hip-hop artist of all time. By far.

Here’s how this best-selling product works. Each headphone contains a neodymium magnet (the strongest known permanent magnet). When an electrical signal from your iPod (or similar) passes through the gold-plated audio cable to the voice coil, electromagnetic induction gives the voice coil a variable magnetic field. The exact strength and timing of the variable magnetic field represent perfectly the music being played. The voice coil’s magnetic field then interacts with the magnetic field of the headphone’s neodymium magnet via magnetic attraction (or repulsion), which moves the diaphragm, which sits between the magnet and the ear. When the diaphragm moves, it creates differences in air pressure (sound waves) that are detected by the diaphragm in your ear.

Excellent sound quality requires an air-tight seal between the headphone’s diaphragm and the diaphragm in your ear. Overstuffed leather guarantees this air-tight fit. Leather requires over 20 treatment processes before it’s ready to use in manufacturing. One of those processes is dying using polyazo dyes. When used in lower concentrations, these dyes are brightly-coloured; when mixed together and used in very high concentrations, they give an overall ‘black’ appearance to the leather.

The Beats® headphone frame is made from strong anodised aluminium. Aluminium, a strong yet lightweight metal perfect for making wearable tech, is anodised to increase its ability to resist wear-and-tear. The aluminium headphone frame is dipped into an electrolytic solution with a ~20-volt direct current flowing through it. Bubbles of hydrogen form at the cathode, and bubbles of oxygen form on the surface of the headphone. This oxygen gas buildup quickly oxidises not only the surface of the headphone, but deep into pores in the surface, which give the frame very high resistance to corrosion. ●

Why are jeans blue? New Infographic: Chemistry of LEVI’S®

Chemistry of LEVI'S® chemistry infographic jameskennedymonash.wordpress.com
jameskennedymonash.wordpress.com

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. ●

Ingredients of an All-Natural Coffee Bean

Following last week’s Starbucks® graphic, it seems right to follow up with a quick poster on the Ingredients of An All-Natural Roasted Coffee Bean.

The Ingredients poster series was featured in Forbes last week (article written by Robert J. Szczerba, CEO of X Tech Ventures).

Follow me on Twitter (@VCEasy) to see all the latest posters (unfinished ones included!)

Ingredients of an All-Natural Coffee Bean
jameskennedymonash.wordpress.com

Why is Coffee so Irresistable? The Chemistry of STARBUCKS®

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.

Chemistry of STARBUCKS jameskennedymonash
jameskennedymonash.wordpress.com

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. ●

RSC runs massive crystal-growing competition open to all students worldwide!

RSC Global Experiment 2014 Art of Crystallography
rsc.org

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.

The RSC has teamed up with the International Union of Crystallography to make this year’s Global Experiment officially a part of the International year of crystallography.

The RSC’s Global Experiment has been a great success in recent years. It follows the 2013 Global Experiment: measuring the quantity of vitamin C in fruits and vegetables, and the 2012 Global Experiment: Chemistry in the Olympics.

For more information, or to register, go to http://www.rsc.org/learn-chemistry/collections/online-experimentation/collaborative-chemistry/global-experiment-2014, and check out some existing entries on their Pinterest board.