Representations

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Representations

Diagram of Many Molecules Reaching Equilibrium

Use large scale diagrams with many molecules to show the progression from initial to reacting to equilibrium, and extend that with changes to the system that influence the equilibrium. In these ensure that there are many molecules present rather than one.

Equilibrium Simulation

Use demonstration or simulation of how both forward and reverse reactions occur up to and at equilibrium in several mixtures. The PhET simmulation below shows both reactions are happening, even though concentration of reactants and products isn't changing.

Link to PhET Simmulation: Reversible Reactions

Emphasize Physical State

Put a bit more emphasis on the physical state of the substance that they are learning about. Because students often aren’t really able to imagine what kind of substance they are going to learn about. They will then know that they don’t have to calculate the volume if it’s a solid, for example, they have to calculate it by mass.

Solubility Demonstration

Use demonstrations when teaching about solubility. Students need to be thinking about what's going on. You have two clear solutions and when you mix them together a white precipitate forms instantly. Then decant the liquid and get them to think about what’s in the supernatant and what is the solid. Go on to use calculations to work out the solubility for an amount of substance. Use the amount that you can see as a precipitate to work out how much is in a saturated solution.

Simulate Dissolution

Use simulations and relate that to a chemical reaction. Eg. CoCl2 → Co2+ (aq) + 2Cl- (aq)

Link to PhET Simmulation: Sugar and Salt Solutions

Demonstrate Reaction During Lecture

Demonstrate a reaction that occurs within the time frame of your lecture. Start it at the beginning of the lecture, and then go back to it in the middle and at the end to show what has happened. For example, you can use copper in silver nitrate solution. 

Link to YouTube Video: Silver Production from Silver Nitrate

Physical Representations

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.

Zinc in Copper Sulphate Demonstration

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.

Link to YouTube Video: Copper Sulfate + Zinc

Copper in Silver Nitrate Demonstration

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.

Particle-Wave Model

Try to show students that the fundamental form of matter is energy. Then that this can be represented as particles with mass or as waves (wave functions). Then try to show them that we use the model particle/wave that best helps us understand different phenomena. In class I often do this by asking questions about wave mechanics in particle terms. eg. If a 2s orbital has a node how can the electron pass accross it? Then explain to them the limitations and advantages of each approach.

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