Excellent Advice for Chemistry Teachers

 The WA 2022 ATAR course examination report for Chemistry offers some excellent advice for all teachers of chemistry,

"Teach general concepts from first principles so that students can apply concepts to unfamiliar situations, not just write everything they know."

If you had shown this to me in 2019, I would have been shocked to think that any chemistry teacher wasn't teaching concepts from first principles, but COVID19 really did fundamentally change the way teachers were forced to teach, and how students were forced to study. "Remote learning" encouraged a return to the "bad-old-days" of rote learning "facts" and "how-to"s as a means to obtaining an end (success in exams). Unfortunately, once these electronic measures had been put in place (rather hurriedly in most cases), nobody seems to want to revisit this hasty construct and replace it with something better. There is a huge opportunity here to begin teaching chemistry as a science, using the scientific method, but no, we continue to teach students how to answer exam questions.

This is not education, it is training. And it is training of the worst kind since the ability to answer exam questions is not very useful in the workforce or in adult life.

Heed the advice, "Teach general concepts from first principles so that students can apply concepts to unfamiliar situations", and bad training becomes great education.

Making it harder to cheat

Here is the problem: teachers want to engage their students with interesting demonstrations and activities to motivate them to think about  a scientific concept. Students, on the other hand, just need a good mark on the tests and assignments so they can become a doctor, or a lawyer, a cobbler or a candlestick maker, etc.

As the technology available to students to help them answer their assignment questions gets better, teachers need to think about how to structure questions to make students think, rather than just google the answer.

Here is an example of a pretty standard sort of test/assignment question; What properties of aluminium make it suitable for use in cooking pots.  Give a disadvantage of using aluminium for pots.

If you copy and paste that into google, there are 2,090,000 results, and the top of the page will read, "Aluminum is lightweight, cheap and very good at distributing heat. It doesn't retain heat particularly well though, so the temperature will fluctuate as food is added to a hot pan. It's also the softest metal on our list, so it will scratch and dent pretty easily."

Assignment done! No thought required!

So we need to re-structure the question. How about this...

On the planet P42da, the element potsnpanium is used to make large pots in which the P42daians heat soup to above the boiling point of liquid water at 1 atmosphere. What properties of potsnpanium make it suitable for this purpose. Give an example of a safety precaution the P42daians should take when handling potsnpanium pots. Describe a way to reduce this hazard.

Copied and pasted into google this yields 0 results and a heap of useful suggestions:

"

• Make sure that all words are spelled correctly.
• Try different keywords.
• Try more general keywords.
• Try fewer keywords.

"

Might force some students to have a think about it.

Food Fraud in Australia?

Congratulations to Dr Michael Smith, Associate Professor Mahmud Ashraf, Professor Chris Austin
and Associate Professor Rebecca Lester of  Deakin University on the publication of "Product fraud: Impacts on Australian agriculture, fisheries and forestry industries" (November 2021). This report gives a good, concise, overview of known recent agricultural product fraud from all over the world. While it can make for scary reading, it is a reminder to stay vigilant when buying food. Here is a little taste of what you will find in the report,

"Turmeric is considered highly vulnerable to food fraud, with
frequent incidents of contamination with lead chromate (a
yellow colourant) reported. A study found that seven of nine
turmeric-growing areas in Bangladesh showed evidence
of turmeric adulteration with lead chromate. Levels of lead
exceeded national limits by up to 500 times (24-9-19)."

You can download a copy of the report at the AgriFutures Australia website: https://www.agrifutures.com.au/product/product-fraud-impacts-on-australian-agriculture-fisheries-and-forestry-industry/

Examples of food fraud can be used when teaching chemistry. Students can calculate the concentration of milk or fruit juice after it has been fraudulently diluted, and then compare that to what is stated on the nutrition panel product label. You can learn a lot about the properties of chemical compounds and mixtures by making a fake egg or fake milk. You could used the adulteration of "manuka honey" to teach spectroscopy, or the melamine (1,3,5-triazine-2,4,6-triamine) in milk scandal to teach percentage composition or volumetric analysis. The pedagogical possibilities are limited only by the resourcefulness of the food fraudsters.

If you are looking for some more inspiration, try "Sorting the Beef from the Bull: The Science of food fraud forensics" (Evershed, R., and Temple, N, 2017). And yes, I may have bought it because it has such a great title ... you all know me too well 😉

 

I Hate STEM Education!

You might think it strange that I hate STEM education since I spend my life encouraging people to study chemistry. It's not the education part I hate, it's the acronym "STEM" and what it stands for.

I recently read an article by Bryan Scaf, "STEM - We know what it stands for, but what does it mean?" (https://au.educationhq.com/news/40140/stem-we-know-what-it-stands-for-but-what-does-it-mean/).
Which started me wondering if we really do have  a shared understanding of the meaning of STEM.
What STEM means depends on who you are talking to.

If you ask a scientist, they will probably tell you that STEM stands for a Scanning Transition Electron Microscope and the first STEM was built in 1938.
If you try asking people in the street, they are most likely to think it has something to do with biology, plant stems or stem cells for example.
Towards the end of the twentieth century, STEM started being used as an acronym for Science, Technology, Engineering and Mathematics (STEM), superseding the previous (and possibly slightly  less ambiguous) SMET acronym. STEM education has come to mean an integrated approach to the teaching of science, technology, engineering and mathematics using an inquiry-based learning model.
So the question arises of whether we  do indeed know what STEM stands for.
In case you are not convinced that "STEM" is ambiguous, head on over to http://www.acronymfinder.com/STEM.html and read through their list of 19 uses of the acronym STEM.
The first reason why I hate STEM is that the term is ambiguous.

STEM (as science, technology, engineering and maths) is a huge area. It encompasses observable, concrete entities as big as the entire cosmos and as small as elementary particles, and, that's just the STE part!  The "M" part is quite nebulous (yes, groan, groan, another bad pun).  Maths is based on numbers, shapes and other abstract entities. So when we lump abstract maths and concrete science (including the applied fields of engineering and technology) together we've pretty much covered everything, making STEM so large and all-encompassing that is a useless concept. You can't teach "STEM", but you can attempt to teach a few scientific concepts which can be applied to problems in engineering and/or technology. You can try the same with mathematics, except that you land yourself in the middle of another problem ....

And this next HUGE problem is the way most (non-mathematical) people think about mathematics, the big "M" in "STEM". Science (including engineering and technology) uses maths (small "m") like a tool, an aid to defining and solving problems and to build models. But this isn't really Maths (big "M"). Maths is based on logical reasoning, but there are differences between scientific reasoning and mathematical reasoning.
The scientific method is, broadly speaking, a form of deductive reasoning. A mathematical proof, the essence of maths, is largely based on inductive reasoning. The way "science" views the world is different to the way "maths" views the world. So why on earth do we lump "M" in with the "STE" ?
If I were a Maths teacher, I would be very concerned that lumping maths in with science, engineering and technology makes it look like maths is just a tool to be used rather than an elegant, logical, reasoning process.

I would make a similar argument for Science (S). Lumping science in with engineering and technology makes it look like science is just a tool to be used to solve engineering and technology problems. Science can be used this way, just like mathematics can be used as a tool, but this is not the most important aspect of science. Science is the systematic study of the structure and behaviour of "the world". Scientific study may lead to a theory or a model which can be used to make predictions, which can be tested, lending support to the theory or suggesting modifications to the theory, etc. It is the results of "science", the theory or model, that can be applied to problems (engineering and technology), but teaching/learning science should not be primarily about the application of results, it should be about understanding scientific concepts.

Let me just add that even within the science (S) part of STEM there are huge differences and difficulties. Chemists are primarily interested in understanding and making patterns with "atoms". Physicists are more interested in the interaction of energy and forces. A Chemist might analyse a rubbery material, then think about how atoms could be pushed around in the lab to make a similar material, or a different material with enhanced stretchiness compared to the original, or with less stretchiness, or the same stretchiness but a different colour, or different melting point, etc. A Physicist might look at the same material and be fascinated by the forces required to stretch the material, how far it can be stretched before it deforms or breaks, or whether its stretchiness depends on how fast or slow it is stretched or on how hot or cold it is, etc. Now you might be thinking that this would form a great basis for a STEM education (inquiry-based learning) activity, but I beg to differ. Indeed, students could probably competently and safely investigate stretchiness of a suitable material and think about how the material might be used (engineering/technology) but what have they learnt by doing this? They will have investigated one example (or maybe a few), and drawn a few conclusions about a specific material(s). But what is the point? Will they actually have any understanding of the chemistry and physics principles underlying their observations, because it is the scientific principles that are really useful, not the results of an isolated experiment or two.
In order to have an understanding of the material they need to understand how Chemists might analyse it, and they need to understand how structure and bonding effect properties. If they want to make a new material based on the structure of the original, then they are going to have to come to an understanding of reaction mechanisms. This in itself constitutes a lot of concepts before we even begin on the physics concepts they would need to understand stretchiness.

The problem with STEM education is that it over-emphasizes concrete application and under-emphasizes abstract reasoning. Mathematics and science are so much more than just "tools" to be applied to solve engineering and technology problems.
Mathematics (M) is based on logical reasoning.
Science (S) is based on logical reasoning.
What is engineering (E) based on? Engineering is the application of science and maths.
So what is technology (T) ? Technology is also the application of science.
So, STEM stands for Science (S), Mathematics (M) and their application (TE or should that be TA?).
I think a better acronym would therefore be S&M. I think students might find that more entertaining than STEM.

Acid-Base Equilibria and Beginner Teachers

Cathy is a Year 12 student in a Brisbane school (capital city of Queensland, Australia). Last week she had a chemistry exam, the topic was equilibrium which included acids, bases and acid-base titrations. I met her on her way to school on the morning of this exam. When I asked her if she felt confident about her exam, I was horrified by her response,
"Sort of. I've got a new teacher this year and she's not any better than the one I had last year. We did an experiment, she said it took too long so we didn't do any more."
Seasoned teachers are used to:

• student claims that their teacher is "no good" (especially if the student is performing poorly)
• student exaggeration (only 1 experiment in a whole term of equilibrium, surely not!)

"Oh come on", I said in my best 'you're kidding me' voice, "you studied equilibrium for a whole term and only did one experiment?"

"Yeah", she confirmed, "we watched a video on titration though".

"Didn't you do a titration experiment?"

"Nah. She said we didn't have time."

Even allowing for the possibility of student exaggeration, the thought that you would play a video showing someone else performing a titration rather than giving your own students the opportunity to carry out even a simple titration, is, quite frankly, appalling. 

From Cathy's description of the teacher I assume this is the teacher's first year out teaching (beginner teacher). Reflecting on my own first year of teaching (a long, long time ago), I remember struggling to meet the requirements of the chemistry syllabus in the time-frame allowed, and, I also remember that while teaching the techniques of titration was time consuming, the students learned more in a few practical sessions than they learned during the whole of the preceding theoretical lessons, and once they have mastered the techniques they can be put to use in real-world problems.

A typical sequence that is often taught for (monoprotic) acid-base equilibria assumes prior knowledge of solutions, concentration (molarity) and equilibrium concepts and calculations (including self-dissociation of water, K_w ):

1. What are the properties of acids and bases?
2. How do we define an acid and a base?
3. What is meant by the terms "strong acid"  and "strong base"?
4. How do we measure the strength of an acid or a base (pH scale)?
5. What happens when you add an (Arrhenius) acid to a (Arrhenius) base (neutralisation)?
6. How much (Arrhenius) acid do we need to add to a known amount of (Arrhenius) base in order to neutralise it (acidic, basic, neutral solutions)?
7. Discussion of titration techniques, including preparation of a standard solution.
8. Performing a strong acid - strong base titration.
9. Using the results of the experiment to calculate the concentration of the unknown acid or base.
10. Perform calculations for each 1 mL addition of strong acid to strong base in the titration experiment and graph the results (strong acid - strong base titration curve)
11. Discussion of weak acids (K_a).
12. Discussion of other acid-base reactions (proton transfer reactions) and other titration curves
13. What indicator should you use for a particular acid-base reaction? (optional, how does an indicator work)
14. Titration of weak acid - strong base (such as determination of acetic acid in vinegar)

If you see your students 4 or 5 times a week, this teaching program for acid-base equilibria will take about 4 weeks using a traditional, structured approach. If you have the luxury of being able to time your practical work so that it occurs in the correct sequence, and take time to link the practical work to the theoretical concepts, your students have a good chance of understanding and being able apply the concepts to unfamiliar problems.

If you don't do any experimental work, you could probably bowl it over in 2 to 3 of weeks, and be faced with a lot of bored students wondering why they ever took a course in chemistry.

If you take a student-centered constructivist approach (for example, start with the questions  like "what gives vinegar its tangy taste?",  "if acids are corrosive and burn skin, how come you can drink vinegar?",  "how can you measure the strength of an acid?", "how can we determine which brand of vinegar has the greatest concentration of acetic acid?"), be prepared to add another week (unless you give the students a lot of reading/research for homework). The benefits, however, are enormous. Your students are more likely to be engaged with the content and "on task", they will have to be able to justify decisions they make in order to design and perform experiments thereby linking concepts and practical work, and because they "invest" in the whole learning process they are more likely to be apply the understanding and knowledge gained to other problems.

So, if you are new to teaching acid-base equilibria, here a few suggestions:

1. Even if you firmly believe that constuctivist approaches to teaching are the most effective way to teach chemistry, be prepared to spend your first year of teaching chemistry taking a more traditional approach, using guided questioning to lead students towards the experiment(s) you need them to do (syllabus requirements) while still giving them "ownership" of the experiment and its results. Keep a list of the misconceptions you come across when you teach, this will help you be better prepared for next year. As you feel more confident in your ability to meet the syllabus requirements within the time you have, and you have a better feel for the misconceptions you will meet, you can start "loosening your hold" and give more time to truly constructivist approaches.
2. Let the students do as much practical work as possible (students not only need to be exposed the practical techniques of chemistry, they need to do the experiments in order to fully appreciate the significance of what you are trying to teach them). You also need to devote time to discussing the results of their experiments with them, and reinforcing the concepts, calculations, techniques etc involved. 
3. Spend time discussing the self-dissociation of water (that is, it is a lesson in its own right, not just a passing reference before you discuss acid-dissociation). Students will have been exposed to an "acids and bases" topic sometime between Years 7 and 10, but even so, many of them may still think that an acid has a pH less than 7, a base has a pH greater than 7, and that a neutral substance has a pH of 7. Believe me, it can be an uphill struggle to separate the two concepts of "acid, base, neutral" from the concept of "pH" in a student's mind (and if you don't believe me, think about the number of times you have seen/heard advertisements for products which talk about the "neutral pH" of skin/hair etc). If the students do not have a good grasp of the self-dissociation of water then they will not understand the pH of  aqueous solutions. (And a word of caution, just because a student can calculate the pH of an aqueous solution of base at 25^oC, it doesn't mean they understand the relevance of pH + pOH = 14, or [H⁺][OH^-] = 10^-14, and if you want to test this statement, ask you students to calculate the pH of 0.001 M NaOH(aq) at 50^oC, or ask them to find the pH of 0.01 moles of HCl(g) dissolved in 1 L of ethanol and see what happens, because the chances are they will simply do a pH + pOH = 14 calculation without even thinking about it!)
4. Spend time making the distinction between "strong acids", "weak acids", "dilute aqueous solutions of acids" and "concentrated aqueous solutions of acids" (similarly for bases) because once again, you are likely to have an uphill struggle to separate the two concepts "strength of an acid/base" and "concentration of an acid/base". Remember, they have already been exposed to statements such as, "I need a cup of strong coffee", or, "this cordial is a bit strong" which, in chemical terms should be "I need a cup of concentrated aqueous solution of coffee (or cordial as the case may be)". On the other hand, they have also been exposed to ads which say things like "concentrated laundry detergent" which is a slightly more appropriate use of the technical term "concentrated" (although I do remember one example that used "concentrated laundry liquid" which introduces the other problem of the loose usage of the word "liquid" instead of "solution"). One way to do this is to give each pair of students a bottle of acetic acid labelled with its concentration, and have them measure its pH with a pH meter. Also provide them with volumetric flask of HCl(aq) of known concentration (say 0.1 M) and have them measure its pH, then have them perform sequential 1:10 dilutions and measure the pH at each stage say they can see that pH is dependent on the concentration of the strong acid and that you can reach a point at which the pH, and therefore the concentration, of a strong acid is the same, and even greater than, the concentration of an aqueous solution of weak acid. When you tabulate the class results and ask them for an explanation be prepared for many of them to believe you somehow "tricked them", it can take time for them to break the strength/concentration misconception and replace it with a more appropriate separation of the two concepts. If the students do this activity themselves, it will easily take a lesson, if you do it as a demonstration it will take about 10 minutes, BUT, it is better for the students to do it themselves partly because it reduces the instances of "there must be a trick in this" thinking, but mostly because they can see the pH change with the concentration and they are going to have to justify that all the way to the point at which the pH of the strong acid is  greater than the pH of a weak acid.
5. Related to point 2 is the common misconception students may have that when you add an acid to a base you end up with a neutral solution that has a pH of 7. Personally, I think the best way to deal with this is to let the students work it out for themselves before you attempt to explain it to them. For example. give each pair of students a bottle of methyl orange indicator (you will need a fair degree of tolerance in establishing the end-point so don't use a pH meter) and a conical flask and have them add a 10.00 mL aliquot of standardised 0.1 M NaOH to the flask and record what happens to the indicator colour. Have them calculate the moles of hydroxide ions in the flask, as well as calculate the pH of the solution (so they are convinced the indicator is giving a true reading). Then give each pair a 100 mL volumetric flask containing 0.1 M monoprotic acid (some will get a strong acid such as HCl(aq), some will get a weak acid such as acetic acid). . Have them calculate the volume of acid they will need to add to the NaOH(aq) to neutralise it. Have them add this volume (straight from the pipette to the flask), give it a swirl, and record the colour of the indicator. Tabulate the results on the board (yellow vs red). Ask them why some changed colour and some didn't (be prepared to let the students with weak acids try adding more acid, many will believe they made a mistake in the calculations or in adding the solutions), if the students do not come to the realisation that only students with strong acids got a colour change at neutralisation, you can use questions to help guide them. I have found this is a far more effective method than just "telling them" and it need only take 15 minutes if all the solutions and equipment are prepared before hand AND you don't expect them to write it up as a prac (a demonstration takes even less time, but may not be quite as effective, that is, some students will believe you have somehow "tricked" them).
6. Have the students perform the calculations that will enable them to draw a strong monoprotic acid - strong base titration curve. If you have a class of 20 students, they only need to do one of the calculations each, you can tabulate the results and then they can graph the class results. There are a number of reasons for this, it reinforces the nature of the neutralisation reaction, stoichiometry, and of "limiting reagents" and "reactants in excess". It is also enables them to come to a greater understanding of the shape of the curve than if you just present it to them and discuss key points. Finally, if the students do not have a good grasp of why titration curves are the shapes they are, they will have a much harder time coming to terms with the nature of different indicators and why some indicators are more appropriate than others for particular titrations.
7. Do use "real-world" examples. The acetic acid concentration of brands of vinegar is not hard to do, and empowers them (if you have mothers whinging that their daughter will now only let them buy brand X because its better value because it has a higher concentration of acetic acid than other brands, then pat yourself on the back for a job well done!) If you are in a position to be able to safely determine the concentration of sulfuric acid in a lead-acid battery, then this is also not hard to do (but check whether it can be done at your school). Similarly, you will find concentrated HCl(aq) available at you local hardware store (for cleaning bricks) or pool suppliers (for addition to pools) and, if your safety guidelines allow, you can determine the concentrations of these.If you are prepared to take your students through back titrations (indirect titrations) then a wealth of new "real-world" opportunities is open to you.
8. Finally, do not deceive yourself. It is NEVER about what you "teach", it is ALWAYS about what the students "learn". YOU can make up time by giving the students notes you have prepared for them, making them read stuff for homework, making them watch a 30 minute video instead of doing a 2 or 3 day prac, then you can happily tick this off on your list of things to teach, BUT, you must also find out what the students have learned, because you may very well find out that you have been a bit hasty in ticking something off your list! 

Why Study Science?

Listen to four of the world’s most eminent physicists discuss and deliberate on the biggest challenges facing the science community today.

• Professor Steven Chu was the co-recipient of the 1997 Nobel Prize for Physics. He has devoted his recent scientific career to the search for new solutions to our energy and climate challenges. 
• Professor Schmidt was jointly awarded the 2011 Nobel Prize in Physics for the discovery of the accelerating Universe.
• Professor Lawrence Krauss is theoretical physicist and the author of several bestselling books, including The Physics of Star Trek and A Universe from Nothing. He is an advocate of scientific scepticism, science education and the science of morality.
• Professor Lisa Randall studies theoretical particle physics and cosmology at Harvard University. Her research connects theoretical insights to puzzles in our current understanding of the properties and interactions of matter.

The podcast is about 1.5 hours, but you can select parts of it to listen to.

There is a very nice discussion of what is meant by "good science", there is also some very interesting discussion on "accidental discovery", "experiment to "prove" or "disprove" theory, and the importance of acknowledging that science is not an "absolute" but rather about belief in the "truth" of a scientific theory based on statistical probabilities.

https://soundcloud.com/experience_anu/when_does_science_matter

A little MatheMagic is needed!

The University of Queensland's Faculty of Engineering  held a networking forum for teachers on 5th November 2013. They expressed a number of concerns regarding the High School graduates entering  the first year engineering course, and I think it's worthwhile highlighting one of those concerns here.

The main academic concern is that High School graduates do not have an adequate background in mathematics to cope with engineering. Now, they were very upfront about this, admitting that part of the problem was that they reduced the prerequisite from Maths C to Maths B in order to attract more school graduates to engineering. For those not familiar with the Queensland education "system", students present 6 final subjects, Maths B is one subject and Maths C is a separate , more advanced subject. Previously, engineering hopefuls would study Physics, Chemistry, Maths B, Maths C, English + 1 other subject. Now, they can present Physics, Chemistry, Maths B, English + 2 other subjects. The assembled teachers weren't very sympathetic to start with, why don't you just raise the prerequisite to Maths C again? Until we were presented with examples of the kind of maths some of the students seemed to be struggling with.
One of the examples we were given was that there were students who believed that if
a + b = -1 then that means that a = -b
and that is a huge concern! But raising the prerequisite wouldn't help, simply because any Maths student in senior high school should have no trouble realizing that a = -1 - b

I've had a similar discussion with a friend of mine who is a lecturer in nursing (at a different university). Her complaint is that High School graduates entering first year nursing often have difficulty with calculations involving drug doses. For instance, students have to decide how many tablets to give a patient given that a doctor has prescribed 100 mg of drug A four times a day, and that the hospital supplies brand X tablets each containing 50 mg of drug A.

High School chemistry and physics teachers are very familiar with this problem. There always seem to be atleast a few students in each class who appear to be quite good at maths judging by their report cards, but who don't seem able to handle fairly simply algebra when they leave the maths class.

Now, before the maths teachers start feeling indignant, let me say that this problem is not restricted to maths, and, unfortunately, it isn't even restricted to students. After the Engineering Faculty's presentation, I was chatting to a science teacher who was telling me about developments in the silicon chip industry that required "water that is so pure it is acidic".Curious, I followed up with a few questions, thinking that this teacher may have been using a definition of acid that I wasn't familiar with, but no, this teacher seemed to be using a Bronsted-Lowry definition.

So, the problem in a nutshell is that we are graduating students from schools with reasonable grades in maths who are not capable of rearranging an equation (and the much worse problem that there are teachers teaching science who don't seem to understand the concept of equilibrium and neutrality).
Clearly, any "learning" that has taken place is only at a very superficial level. How can we address this problem?

Periodic Table Teaching Resources

AUS-e-TUTE has downloadable resources related to the teaching and learning of Periodic Table concepts.

Visit http://ausetute.com.au/downloads.html to download:

• Interactive Periodic Table (only for Windows)
• Lesson Outlines for teaching Periodic Table concepts (designed to be used with AUS-e-TUTE's interactive Periodic Table)