Silicate Mineral Structures and Viscosity
We will demonstrate the activity itself, if enough of an audience is available.
First year science students in introductory geology struggle with the concept of silicate structures, tetrahedral bonding, Si:O ratios and also later the concept of magma polymerisation and viscosity. This activity is a collaborative demonstration of those concepts. It starts with groups of four students (oxygen anions) taking hold of the four ends of two pieces of rope tied in the middle (the silicon atom). To demonstrate increasingly complex silicate structures rope bundles are linked by humans (the oxygens) in chains, sheets and finally framework structures as students take ends of bundles with both hands. The seated audience assists in counting the Si atoms and the O numbers for each increasingly complex structure.
For polymerisation/viscosity I have each increasingly complex rope group try to walk about the room. Simpler structures such as single tetrahedra groups move about more easily. I also demonstrate how easily I can roam between isolated structures vs highly polymerised structures. I formatively assess the concepts through a silicate structure (Si:O ratio) worksheet that we do together. The same material is also assessed through exams.
It can be used informally and quickly in the front of a large lecture hall, or for a more in-depth demonstration in a practical.
Why It Works
It is effective because students learn by doing. It is worthwhile because these are first year students who by and large do not know each other. The activity occurs early in the semester and serves as an ice-breaker.