Teaching graphite & fullerenes?

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I recently came across a topic to teach from GCSE AQA Module 3.  Students aiming at grades 1-4 had to acquire a clearer understanding of the difference between graphite and fullerenes.

Students know that graphite is a form of carbon and they usually can relate to this in comparison to diamond as an allotrope of carbon at this stage. It is vital to keep their understanding clear and keep the facts simple.

I began with asking students to compare the structures between graphite and fullerene.

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Students came up with comparisons of what they could see being the key visual differences between the two molecules.

They verbally expressed that a) They were both giant molecules

                           b) They had hexagonal ring structures (6 carbons).

                           c) There was layering in both, but graphite had clearer layers.

They also established a key difference- that fullerenes seemed to have hollow shapes.

Next, I explained to them that they both had delocalized electrons within the structures. The students naturally did not understand the term delocalized. I first gave them a definition:

'A delocalized electron is an electron in an atom, ion or molecule not associated with any single atom or a single covalent bond.' I went on to discuss that if something is localized it would naturally stay near a particular area. I had to remind them that electrons were negatively charged particles and reinforce their model of the Atom. Then I explained that if I lived in Nottingham and went to another area such as Manchester to do my shopping I was not actually staying locally. I was traveling, I was delocalized. These electrons flutter- they don't stay around one particular atom, ion or molecule.

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The students understood this and so we moved forward. One student pointed out that when she had researched fullerenes that some had hollow tubes. I explained that these were nanotubes and in this example, we were looking at Buckminsterfullerine- the C60 model in comparison to graphite.

From the electrons moving around, we next posed a question as to whether or not the fullerene would be a good conductor. One student used his prior knowledge and pointed out that since non-metals didn't conduct electricity this one wouldn't. Another student said that he knew that current was a flow of electrons and that flowing current was the same as flowing electrons. The debate continued in a controlled manner but the input began to become a bit fierce at this stage, with each student arguing his or her opinion using logic. Some students sided with the student they thought that was always right. Others remained neutral participants, acting as mediators.One offered to try it out. 'Miss, can we have some graphite please to see if a bulb lights'. I had this equipment ready and offered my assistance to keep him safe. He tried it out and it worked. Students were not convinced about C60 and since I didn't have any to test the debate continued. It was as if the lesson was full flow. In the end, after a class vote, the students decided that both graphite and Fullerene would conduct electricity.

To conclude we tried a past exam paper that I had found from the exemplary tests from the exam board's website. Students swapped and marked each other's sample answer using the mark scheme and grade reference.

They wrote a short tweet in their book about what they had learned. It was 50 minutes well spent. The lesson was a success because they had reached their target grade and had used their intelligence to have a memorable learning experience. Many students looked forward to the following lessons and this was rewarding enough for me!

Sheila Emery

(Chemistry teacher/Science blogger)

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