A billion times smaller than us: helping students comprehend the molecular scale

Abstract

Comprehension of molecular scale is an essential component of a chemistry student’s education. However, it is especially difficult for most to wrap their heads around just how small the nanometer scale is at which the molecules they are taught about exist. Using 3D printing techniques to aid in visualization, we can model spherical molecules, namely buckminsterfullerene (C60) and the cuboctahedral gold cluster Au55, and scale them up by eight orders of magnitude. The new size of these molecules is comparable to a globe 13 cm in diameter, a model of the Earth scaled down by eight orders of magnitude. Seeing and holding both of these objects resized to similar dimensions, students are able to get a sense of how the molecular scale compares to the handheld scale. The fact that the molecule is scaled up by a factor of 1024 in volume also nicely contextualizes the magnitude of Avogadro’s number (∼0.6 × 1024), the constant of proportionality that converts the molecular scale to the handheld scale.

Keywords

• chemical education research
• first-year undergraduate/general
• hands-on learning/manipulatives
• high school/introductory chemistry