Students will learn that size does matter. They will investigate how changes in the shape or size of an object affect its surface area to volume ratio (SA/V), which can change dramatically in the nanoscale. When they complete the Activities, they will apply this knowledge to design an “exploding” liquid geyser.

By incorporating everyday materials into science lessons, the Materials World Modules (MWM) program at Northwestern University has found the solution to getting students excited about learning science while helping teachers meet national and state education standards.

The modules are easy to organize and inexpensive to run. They can be incorporated into any science class because of the breadth of subjects covered in the Activity and Design Project sections. Each module is a supplemental science unit that takes 1-3 weeks of class time (approximately 10 hours) to complete.

» Module At-a-Glance
» Connecting to Your Curriculum

Activity 1: Size Dependent Properties
The importance of an object’s size manifests itself most significantly through interaction of its surfaces with the surrounding environment. This “hook”activity presents some intriguing phenomena that pique students’ interest in surface area effects, i.e., how physical form and size of a solid influences the degree to which it interacts with its environment. They find that the more finely divided (or more spread out) a solid is, the more surface is available for
this interaction.

Activity 2: Powers of 10 and Scale
Students get a feel for dimensions (or size of objects) that are very different from our ordinary experience, with examples in the range of 109 to 10-9 meters. A most useful concept for this purpose is scale. Activity 2 also emphasizes the representation of scale in ways that make it easy to understand (effect of changing size by a factor of 10, or stepwise change in orders of magnitude).

Activity 3: Surface Area and Volume
To help students realize how and why surface area to volume ratio (SA/V) changes dramatically in the nanometer scale, students construct objects that varies in size, as well as shape. They begin by looking at twodimensional (2-D) behaviors involving perimeter and area, which has analogous relationship as surface area and volume, followed by exploration of how SA/V changes with the size or shape of 3-D objects.

Activity 4: Playing the Nano Concept “Nanocos” Card Game
The Nanocos game combines two big ideas in nanoscience— SA/V and size and scale—into an engaging environment suitable for reviewing module concepts, as well as for a novice to learn nano concepts and their roles at the nanoscale. Students play the interactive “dueling” card game with game play involving manipulation and comparison of SA/Vs of differing sized and shaped objects that vary widely from 1011 down to 10-19.

Design Project: Designing a Liquid Geyser
Students are challenged to apply the concept of SA/V to a real-life experiment. They begin by evaluating the familiar “Coke™ fountain” experiment resulting from the heterogeneous nucleation of carbon dioxide gas on the surface of Mentos™ candy. Their task is to increase the SA/V and create a high surface area alternative to Mentos to make the soda “geyser” go higher.

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Materials World Modules are designed to be easily incorporated into any middle school science or high school science lab or lecture course. The chart below lists the subjects covered in the Activity and Design Project sections of this module.

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