This is a really fun Challenge where student use two colors of marbles to simulate close packing. It culminates in them creating the face-centered cube "hidden" in hexagonal close packing.
Boxes (typically from disposable pipettes), clear and blue marbles about 12 mm diameter, 20 mm water bath balls (VWR), small ruler.
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This is always enjoyable and moderately challenging. Some groups will need some help along the way.
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