How I teach - Creating compound interest

Reveal organic chemistry’s fun side with a lesson on ingredients

4th April 2014, 1:00am

I love organic chemistry - not just for the aromas of orange, ylang-ylang and pineapple that linger for hours in the lab after an esters experiment, but because it is so relevant to our daily lives. Organic chemistry is the study of medicines, hormones, vitamins, flavourings, perfumes and nutrition. It is the foundation for all the biological sciences, because all living things are made up of organic chemicals.

Sadly, not all students share this view. Some see organic chemistry as abstract and irrelevant: a subject with confusing drawings, complicated reaction mechanisms and bewildering chemical names (such as 2-methyl-3-buten-2-ol).

There is also a common misconception that organic chemistry has no connection to everyday life. I saw an opportunity to correct this among my students, so I planned a lesson called “Ingredients”. This is how it works.

First, I challenge students to read the ingredients list on a bottle of moisturiser with perfect pronunciation. Nobody can do it. Then I emphasise that organic compounds are all around us - including in our food.

Next, in groups of four, students brainstorm some of the all-natural ingredients of the various fruits I have placed on their desks, including bananas, pineapples, blueberries and lemons. They struggle at first, but within a few minutes each group has jotted down dozens of ingredients with the help of their biology books and the internet.

As a visual hook for this task, I designed a poster called “Ingredients of an all-natural banana”, listing the organic make-up of the fruit. The students always love it.

Then I tell students that we are going to learn how to draw some of these organic compounds, starting with the most basic one: methane (CH4). I build a model of methane by tying together four yellow balloons (“Sir, were you once a clown?”). I point out the tetrahedral structure and emphasise that the students will need to draw organic molecules tetrahedrally in the exam if they want to get full marks.

Next, we practise sketching some molecules. I draw three very simple organic compounds on the whiteboard (methane, methanol and ethane) and ask the students to draw five more (ethanol, propane, propanol, butane and butanol). They start to see a pattern and, in doing this, they find out about carbon backbones and learn their first functional group: the alkanol group.

At this point, we are ready to write down 100 organic compounds. I ask the students to draw a table in their notebooks: 10 columns for 10 functional groups and 10 rows for the carbon backbones from C1 to C10. They will finish labelling this table for homework.

I am always thrilled with the outcome of this lesson: the students get much more excited than I anticipate. The lesson is an introduction, but the rest of my organic chemistry course is taught in a similar way. When studying esters, for example, students design their own perfume from a range of alcohols and carboxylic acids.

An added bonus for me was that my banana poster ended up going viral after someone posted it on Reddit. To date, it has had more than 2 million views. It has received 130,000 “likes” on Facebook and has been featured on news websites worldwide, including on the New York Times site. I am very proud to have brought organic chemistry to a much bigger audience.

James Kennedy is a chemistry teacher at Haileybury, a school in Melbourne, Australia