Teaching Aid Wish List: November 2019



  • What can we make for you in November?



  • Snow flake crystals: A request from skitz1832: Not just stellar crystals, but bullet, spacial dendrites..all of them. Winter is upon us.. Let the interpretation begin!



  • Any other requests for new teaching aids? Would anyone want to re-nominate one that was not the winning model in a previous month?



  • Last day to vote for the next teaching aid we develop. Vote for snowflake crystals or suggest a different model and get some friends to vote for it!



  • Snowflake crystals will be the November teaching model! @Skitz1843 , we will work with you to tie these models to a next generation science standard so that they can serve many teachers and nature interpreters.



  • Great! Whoot!
    What do you have in mind?



  • @Skitz1843 Hello Skitz1843! Not sure, but will research a few diverse kinds of snow crystal forms and get designing. Do you have any ideas how to link this to a teaching standard, preferably a Next Generation Science Standard? This may be more of a nature interpretation model, and that is okay as well.



  • Another thought regarding this model---there may be something in the physics/chemistry realm to do with water bonding into crystal form that would allow this to meet a teaching standard as well as an interpretative standard. What do you think?



  • How do you build a water crystal, i.e., snowflake, from the ground up? Start with a water molecule! I am going to use this winning model as a vehicle to develop a lesson on hydrogen bonding and crystal formation. Of course, if you just want to skip to the end result, that is fine as well.
    As a first sneak peak, I give you the water molecule complete with hydrogen bonds at precisely 104.5 degrees to each other. Next up, the basic crystal building block.
    Snowflake_01.jpg



  • Why do snow flakes tend to form as 6-armed stars? Because of the way that the water molecules bond. This image is the basic building block of a water crystal. Note that there are 3 molecules in each of two orientations. This form then repeats in various ways to create the larger ice crystal or snow flake. Keep watching here for the next step---the larger crystalline structure.
    Snowflake_02.jpg
    In the meantime, how would you like to have these models? As separate models or as 3-d features each sticking out of a single plate, as we did with the butterfly life cycle?



  • Here is the basic sub-unit of a water crystal that forms snowflakes or ice. The blue and grey molecules designate two separate rings of 6 molecules each bonded one above the other.
    Snowflake_03.jpg



  • So how do we take students from 12 water molecules to a snowflake? We first superimpose a simplified model of the 12-molecule sub-unit, a hexagonal prism.

    Snowflake_04.jpg

    Then, we use this crystal sub-unit to start building the ice crystal. Note that there are 8 faces onto which the second sub-unit can be bonded. Building straight outward from these faces will result in "spines" that are either 60 degrees apart in a single plane, or 90 degrees to that same plane and perpendicular to it. This shows why snowflakes tend to have 6 spines on them. It also explains why ice crystals forming, for example, on a flat surface in a freezer will have the occasional spine that goes straight out from the surface.
    Snowflake_05.jpg


 

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