Teach your 14–16 students how to apply their knowledge to new scenarios and they’ll sail through their exams
A key skill of a scientist is to be able to take a body of knowledge, or a set of skills and techniques, and apply them when explaining phenomena and evidence they have collected. We ask students to do the same when we set them exam questions in which the knowledge is put in a new context. However, students find this aspect of the assessments the most challenging.
It is impossible to second-guess what new context examiners will ask students to apply their knowledge in. Therefore, it is important we both provide students with opportunities to practise applying their knowledge in new contexts and teach them strategies to help them to do this.
The organic chemistry topic provides an excellent opportunity for just this. Organic compounds and materials play a vital role in our everyday lives (and in life itself) meaning new contexts are plentiful. The chemistry used in their isolation and production also requires the students to apply prior learning from a range of topics.
Break down misconceptions around changes of state
A common student misconception is that breaking of covalent bonds occurs during changes of state. Comparing cracking with fractional distillation, and the different conditions needed, allows for this misconception to be addressed directly. I like to use models to help students visualise what is happening in these two processes on a molecular level.
In the first lesson, students are challenged to use molecular model kits to make hydrocarbons of varying lengths, which are then mixed together to form crude oil, before being separated out based on chain length and boiling point. We do this on a fractional distillation tower mock-up made from different coloured sheets of paper to represent the tower’s temperature gradient.
Provide students with opportunities to practise applying their knowledge in new contexts and teach them strategies to help them to do this
In the next lesson, models of long-chain hydrocarbons are cracked into shorter alkanes and alkenes illustrating visually the breaking of bonds. One of my particular favourite modelling activities is to ask the students to line up outside the classroom door, joined together in a long chain, each person connected to the next holding a straw. As the students enter, I cut the ‘bonds’ (straws) at random with a pair of scissors breaking the one long chain into several shorter ones. No further explanation is given at this point. After introducing cracking, I then ask the students to relate their learning to the activity at the start of the lesson.
A direct comparison of the ‘separation’ of molecules seen in fractional distillation and the ‘bond breaking’ seen in cracking emphasises the difference between the two processes.
You can follow modelling activities such as these with questions to test student understanding; try the questions in the Cracking hydrocarbons organic chemistry context worksheet.
Illustrate the importance of stoichiometry
Students learn how to balance a chemical equation relatively early in their chemistry studies. However, the concept of reaction stoichiometry can seem very abstract. The methane rocket experiment provides an excellent context for students to see the importance of the perfect reactant ratio.
If you use small carbonated drink bottles (250 cm3 or less), you can challenge students to fill the bottle with different ratios of methane and oxygen and launch the rockets in turn to see which is the most successful. Working out the best method to fill the bottles with precise volumes of gas provides an additional challenge and requires the students to apply their practical skills in a new context.
Navigate common polymerisation fallacies
When teaching polymerisation, I find that live drawing the stepwise process needed to draw a polymer from its monomer by hand on the whiteboard helps students avoid the common errors of incorrect connectivity and misplaced atoms. See the steps needed to draw addition and condensation polymers successfully from their monomers:
Once you’ve live drawn the process, give students individual whiteboards to help them apply the same process to unseen monomers such as those found in the worksheets on addition polymerisation and natural polymers. The ability that a whiteboard provides to erase bonds or atoms and then draw in new bonds removes any temptation to change the bonding anywhere else in the molecule.
Visit the full collection of organic chemistry worksheets for more opportunities for students to apply their knowledge in new contexts.