If you look at the resources - students’ have textbooks, they have electronic media, they have Sapling. They can do the problems in their own time in a guided way with something like Sapling. All we as lecturers have to do is give them the framework to solve the problems.
Link this topic to organic reactions since a lot of them are actually acid/base reactions. That is, there is one species that’s electron rich and one that’s electron poor.
Start with HA and move on to specific chemistry. Reinforce pKa and connect with buffers by asking students to pick conjugate acid/base combinations to make up buffers with different pH. Use the concept that adding strong acid to a buffer converts it to a weak acid, increasing the overall concentration of weak acid.
There are only about three key principles that they need to know from this topic at first year level. All of it comes back to understanding equilibrium and buffers. Because if they understand buffers (which involves understanding weak acids and weak bases, conjugate acids, conjugate bases, equilibrium, Ka, Kb) then they can immediately understand titrations and all the concepts that they need because they’re encompassed in the concept of a buffer. If they’re dealing with either biological or chemical systems they’ll deal with buffers.
Use everyday examples. A great question to have at the end of your lecture would be ‘What is reduced when my bike rusts?’ They might understand that their bike rusts, but what is reduced? Oxygen and water are reduced. But we don’t see the reduction, we just see the iron changing. You have done your job well if someone asks the question ‘What is reduced when my bike is oxidised?’
Use little cartoons or even just physical representations. Have a jar of marbles representing electrons and move them around. Because sometimes having physical things to manipulate helps with understanding of a concept. Even though in reality it’s nothing like it, it’s just a representation.
Put zinc metal in copper sulphate solution and record it with the visualiser. Have it running as you talk about the push and pull of electrons. Then bring it up and say, ‘look what’s happened here, the zinc has rusted’. Students make more of a link when they see things being visualised. The oxidation of metal has a very visual impact on them. But then, they might forget about the reduction side, so you need to remind them of it.
If you put copper metal in a silver nitrate solution, the solution becomes blue and you get silver metal. Ag+ is becoming Ag and Cu is becoming Cu++. The students see both oxidation and reduction happening - and happening at the same time. If you do it close to Christmas you can use the copper filament to make a Christmas tree, and then you get a nice silver on the Christmas tree. They know that it was a colourless ion solution, but then they can see silver on the Christmas tree. So they can easily see the reduction.
Use drugs as an example of the relationship between how much of a species is protonated and how much is non-protonated. This is an equilibrium process. For a carboxylic acid drug, if it’s protonated it’s not ionic, if it’s not protonated it’s anionic. And if it’s going from gut into blood for example, whether or not it goes through the membrane will depend upon the pH of the system.
Ask the students to look at structures and consider what charge different parts of the molecules will have when they are protonated and deprotonated (eg. COOH to COO- is neutral to negative, and NH3+ to NH2 is positive to neutral, but can have OH groups that become O- sometimes, depending on the pKa). Use a table of amino acid structures and pKa values, and get them to work out charges at the pH of interest.
