Click to download REDOX RULES posters for VCE Chemistry
What’s redox? We never learned that!
Yes, you did. I use the term “redox” to refer to all of the following chapters in Heinemann Chemistry 2, which you will have learned at the end of Term 3 (September).
Chapter 26: Redox (revision of Year 11)
Chapter 27: Galvanic Cells
Chapter 28: Electrolytic Cells
Don’t underestimate redox
The VCAA has consistently used redox to discriminate which schools and students have the self-discipline required to keep studying at the end of the year. Studies show that redox is taught at a time when student motivation is at its minimum: energy levels are low, emotions are high, and graduation is just over the horizon. Many schools and students gloss over these topics because they’re running out of time, any many students think they’ve grasped the topic – when they’ve actually grasped misconceptions instead.
Here are some popular redox lies (misconceptions)
LIE #1: The polarities switch during recharge Nope. The polarities never switch. It’s the labels of ‘anode’ and ‘cathode’ that switch because the electrons are flowing the other way through the external circuit. Polarity is permanent.
LIE #2: Hydrogen fuel cells don’t emit any greenhouse gases Wrong. They emit H2O, which is a powerful greenhouse gas. If you don’t believe that the VCAA can be this pedantic, think again. Read their 2015 Examiners Report here.
LIE #3: Each mole of electrons forms 1 mol Ag, 2 mol Cu or 3 mol Al in a cell Wrong again. If you look at the half-equations, you’ll see that each mole of electrons actually forms 1 mol Ag, 1⁄2 mol Cu or 1⁄3 mol Al. That’s why I teach “1, 1⁄2 and 1⁄3 moles” instead of the typical “1, 2, 3 moles” rule.
LIE #4: Temperature increases the rate of reaction in electroplating
Wrong! Remember that Faraday’s first law states that m ∝ Q. Because Q = I×t, only those two things – current and time – can affect the mass deposited at the cathode.
LIE #5: Electrons always leave the anode and go towards the cathode Wrong again. Electrons go RACO: to see what that means, download the posters above. This question appears in recent versions of Chemistry Checkpoints. Give it a try.
LIE #6: The cathode is always positive Ask your teacher.
LIE #7: Ions flow one way in the salt bridge
Nope. Anions always migrate to the anode; and cations always migrate to the cathode.
LIE #8: KOHES always works for balancing half-equations
KOHES only works for cells with acidic electrolytes. For cells with alkaline electrolytes, which sometimes appear in VCAA papers despite not being in the study design (see page 46 here), you’ll need to use KOHES(OH). Here’s KOHES(OH) explained:
Do KOHES as normal
Add the same number of OH–(aq) ions to each side of the half-equation to balance out the H+(aq)
Cancel and simplify. Remember that H+(aq) + OH–(aq) makes H2O(l). Remember also to cancel out any remaining H2O(l).
LIE #9: I can balance an unbalanced redox equation by putting numbers in the equation Don’t be fooled by this one! The ONLY way to balance an unbalanced redox equation successfully is to do the following:
Separate it into two half equations
Balance them using KOHES or KOHES(OH) as appropriate
Multiply them and recombine
Cancel and simplify
That’s a lot of work but it’s the only way to do it successfully. If you try to ‘cheat’ by just writing numbers (molar coefficients) in front of the reactants and products, you’ll find that the charges don’t add up, and you’ll get zero marks for the question.
LIE #10: I can break up polyatomic ions to make balancing half-equations easier
Nope! You’re only allowed to separate aqueous species in a half equation or an ionic equation. Because the Mn and O are actually bonded together in a polyatomic ion, you’ll need to write this:
If in doubt, keep it intact and it’ll cancel out by the end if it’s a spectator ion.
LIE #11: The two reactants that are closest together on the electrochemical series react Not always true. Use SOC SRA instead, which is explained in the posters above. Still struggling? Ask your teacher or tutor for help.
LIE #12: Oxidants are all on the top of the electrochemical series They’re actually on the left, and all the reductants can be found on the right side of each half equation in the electrochemical series. There is no top/bottom divide on the electrochemical series: only a left/right divide of oxidants/reductants.
Decorate your school/bedroom/hallway
Surround yourselves with truthful redox revision using these 17 free Redox posters. I’ve had these up around the whiteboard for a few weeks now – they’re a constant reminder to students that redox has many ideas that are always true.
One more tip: print and laminate an electrochemical series (available here) so you can annotate it during dozens of practice dozens without wasting paper. Good luck!
It’s been two years since I posted the All-Natural Banana. Motivation behind this poster was to dispel the myth that “natural = good” and “artificial = bad”. It’s been a very successful project. It’s spawned 11 more “Ingredients” posters, a successful clothing line, and has sold thousands of print copies worldwide via this website.
Ever wondered why ‘formic acid’ is so-called? Or montanic acid? Or melissic acid? This handy A3 poster shows you the Latin/Greek/Persian origins of each of the carboxylic acids’ common names from ‘formic acid’ (no. 1) to ‘hexatriacontylic acid’ (no. 36). Each acid comes with a cute graphical description of where its name comes from.
There are some interesting origin stories behind each of these names. Formic acid, for example, is found in insect stings (hence the name). Palmitic acid is found in palm trees (hence the name), and myristic acid is found in nutmeg.
Three of the carboxylic acids are named after goats: caproic acid, caprylic acid and capric acid. Together, these three molecules comprise 15% of the fatty acids found in goats’ milk, and many reports also suggest that they smell ‘goat-like’!
Many of the odd-numbered higher carboxylic acids are rarer in nature and thus didn’t earn a common name until recently. Undecylic acid, for example, which has eleven carbon atoms in its backbone, is named simply after the Greek word for ‘eleven’.
The first project of the collaboration used a 4K UltraHD camera to capture beautiful chemical reactions in specially-designed glass containers that eliminate the problems of refraction and reflection caused by rounded beakers and test tubes. I also love how the researchers play with time, slowing down and speeding up the videos at just the right moments. The video footage is then annotated and matched perfectly with background music to give a truly mesmerising result. Here are three of my favourites:
Yan Liang, like the visionary data-visualisation gurus David McCandless and Hans Rosling, is passionate about bringing hidden data to the public domain in a form that’s really easy to digest. When I asked him what inspired him to make these videos, he said:
“To me, science is beautiful and full of wonders. However, the beauty of science is often hidden inside research laboratories and buried in scientific literature. By creating engaging visuals and make them available to the general public, I believe more people would appreciate the beauty and wonders of science, and hopeful get interested in science.”
“The goal is to bring the beauty of chemistry to the general public. To many people, Chemistry might usually be associated with pollution, poison, explosions, etc. We want to show them the other side of chemistry, which is much less well-known. We also want to get more kids and students interested in chemistry and inspire them to learn more chemical knowledge.”
Since Yan Liang, Edison Zheng, Jiyuan Liu, Xiangang Tao and Wei Huang launched Beautiful Chemistry on September 30th, 2014, they have received over 110,000 unique visitors and over 2 million page views. The project has been a huge success, and has already inspired young people worldwide to pursue Chemistry.
“People love our videos of chemical reactions. Some people commented if they saw these videos when they were in high schools, they might work harder and learn more chemistry. A 15-year old student from Germany and others told us our videos inspired them to shoot their own videos of chemical reactions. Artists like these videos and many request our footage to make music videos.”
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.
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).
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.
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! 😉
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.
The first three posters in the series were My Greek Physics Alphabet (which went viral on the internet), My First Physics Alphabet, and My BIG Physics Alphabet. They teach Physics notations in a kindergarten-friendly medium. The posters include B is for magnetic flux density, Q is for electric charge, I is for current and Z is for atomic number. They also include a few notations that make sense to non-physicists too, like “M is for molar mass”.
The fourth poster is called My Blackboard Bold Alphabet and features V is for Vector Space, J is for Irrational Numbers and H is for Hamiltonian Quarternions, along with more familiar notations, like R is for Real Numbers.
I hope this poster set encourages at least one young person to pursue math & science.
Click the banner to get your hands on these posters. They’re child-safe, laminated, and arrive flat with free shipping! Enjoy! 😉
I’m obsessed with print. I love typefaces, I care about using the right quality paper and inks, and I’m fussy about alignment, kerning and line spacing. And that’s why I decided to sell “Ingredients” poster prints.
I’ve got one of each of these prints, and—Wow!—they look so much more gorgeous in real life than on-screen.
Ordering prints is a less formal affair than the T-Shirt Store—just cover my costs via PayPal and I’ll get the prints on the way to your address within 24 hours. Click the Order Prints tab in the website’s ribbon to get your hands on some of these “Ingredients” prints.
Oh—and they’re cheap. Just $10 each and worldwide shipping is available 🙂
Order one to help spread the word. I’ll even sign them if you like 😉 James