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David
Thank you for pushing forward some of these practical ideas that have been developed at CLEAPSS. They were initially answers to safety and cost problems at first but in your words, the educational advantages become apparent. You did not have enough space for the little Hofmann but the electrolyte is sodium sulfate solution, not 2M sulfuric acid as used in a large Hofmann, which is why bromothymol blue can be used to indicate the acidic and alkaline at each electrode. (Other indicators are affected by the oxygen (at a little ozone) coming off at the anode positive electrode.) With 5 ml of hydrogen and 2.5ml of oxygen and can get a squeaky pop in a test tube and relight a glowing splint. Which may surprise teachers who think this is all too small. “Dynamite” soap bubbles can be made and 7.5 ml the gas mixture will knock your socks off (forget balloons) and I can fire plastic pipette bulbs with the energy from that reaction but there is a trick to that if you want to send the blub over 10 metres into the air.
Teachers should also be aware of the CLEAPSS conductivity indicator, again using carbon fibre rods, in which a LRD lights up in tap water but not in distilled or deionised water. But if 1 grain (yes 1 grain) of salt is introduced into a 1.5cm diameter puddle of pure water on a polypropylene sheet the LED lights up. The sodium chloride has dissolved. The electrostatic attraction of water molecules to ions outweighs the electrostatic attraction of sodium and chloride ions in the crystal. And ye in many text books, the ionic bond talk of as a “strong” bond.
You write “Most UK examination boards allow teachers flexibility in how electrolysis experiments are carried out and in the choice of solutions investigated” but at the Technicians meeting at Hatfield yesterday, the technicians said that teachers will do not do these experiments because they think that being “micro” the students cannot manipulate the parts, cannot see what is happening and it is not the equipment in the text book which will penalise them when students take exams. These procedures are there to teach with, not just for examinations. The availability of visualizers, webcams and digital microscopes makes these techniques come alive on the projection screen.
You might righty remove the words anode and cathode from the article but teachers will not because there will be exam points for that. The idea that you can PROGRESS to these terms is not easy in teaching when books are full of the words. We do tend to overload our students with words and ideas in one fell swoop instead of progressing with ideas from one year to the next up to GCSE.
Unfortunately attempts to provide teachers with CPD on items like this do not recruit due to limited funds being available for this type of CPD which is why RSC outreach is so important. Teachers will see some of these procedures on July 4th at a meeting in Birmingham on July 4th (http://www.rsc.org/events/detail/25676/transitions-chemistry-from-8-to-18-and-beyond) and at the VICE meeting in York, http://www.rsc.org/events/detail/26401/Variety%20in%20Chemistry%20Education%20and%20Physics%20Higher%20Education%20Conference%20(ViCEPHEC)%202017.
Bob Worley (www.microchemuk.weebly.com)