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The concepts needed to understand nanoscale phenomena are not new to STEM; however, they need to be presented in a new light. The i-MWM presents the most fundamental nano concepts in a fun and engaging way, integrating various science and math concepts with engineering design to create a coherent, integrated STEM curriculum. i-MWM is fully aligned with state standards, Next Generation Science Standards (NGSS), and Common Core standards. 

The "Intro. to the Nanoscale" module begins by presenting why nanoscale science and technology is important. It then leads to a series of engaging, hands-on activities illustrating how size does matter and how it can have profound effects on properties and behaviors of materials. The next section guides students to the "how and why" of using appropriate tools to determine size of objects and things.This leads to the next activity where the module helps students understand the various ways our observable universe is categorized according to size and scale (in 1D). To help students truly appreciate nano phenomena, the next activity in the module guides them to explore properties of surfaces (2D), volume (3D), and the surface-to-volume ratio (SVR) and examine their impact on surface- and volume-dependent processes. As a final culminating activity, students are challenged to choose a material to maximize the total available surface area to nucleate carbon dioxide (CO2)gas bubbles in a carbonated liquid in order to generate a soda geyser. Students also have the option to conduct second design project to use properties of nano particles of titanium dioxide (TiO2) to maximize the artificial photosynthetic reaction in dye-sensitized solar cells for green energy application.

 

 

Here are the core concepts and their descriptions:

Core Concepts 6-8 9-12
Size-Dependent Properties The physical form of a solid influences the degree to which it interacts with its environment. The more spread out the solid is, the more readily it interacts. The chemical and physical properties of matter can change with scale. As the size of a material approaches the nanoscale, it often exhibits unexpected properties that lead to new functionality.
Measurement & Tools Tools and instruments determine what is accessible to measure, detect, and manipulate with precision and accuracy. Development of new tools and instruments help drive scientific progress. Recent development of the AFM enables investigation of nanoscale matter with unprecedented precision and accuracy.
Size & Scale Size and scale help describe and categorize properties of matter and natural phenomena from extremely large to extremely small. The size of objects and phenomena in the nanoscale can be represented with powers of 10 and scaling.
Surface to Volume Ratio The ratio of boundary to interior space (area/volume) of 2D and 3D objects depends on shape and scale. The surface area to volume ratio changes nonlinearly with the size and shape of an object. This ratio changes exponentially at the nanoscale.

SDP—In 6-8 grade, students work with 2 materials they are very familiar with, candy/sugar and antacid tablets. First, they start by comparing the reaction rates of two different forms of antacid tablets and water (with a few drops of dishwashing soap). Students crush one and leave the other tablet intact. They monitor the rising of the foam in a graduated cylinder as a function of time as carbon dioxide gas is released from the reaction. They also determine dissolving times for sugar in different forms (mint, granular sugar, powered sugar, ribbon candy, and cotton candy). Students learn that objects interact with their environment at their surfaces, and that as a material is more finely divided, more surfaces are available for this interaction (chemical and thermal).

SDP—In 9-12 grade, students first explore how size affects chemical properties of a substance. They add water to two different sizes of superabsorbent polymer (pellets and powder), and observe the dramatic difference in absorption rates. They then investigate how changing the size of gold nanoparticles affect their color. Students add drops of sodium chloride salt solution to the reddish-colored colloids to observe the colloid solution turned to a bluish solution. When sugar solution is added they found no change. In the third part, students examine size-dependent forces. First they did a quick comparison test on how the particles of granulated sugar, powdered sugar, and submicron-sized ZnO powder will behave when pour out of a cup. Then they add a little bit of water to some ZnO powder, which turned to a peanut butter-like sticky paste (due to van der Waals forces). They were able to dramatically alter the viscosity of the thick mixture by adding a few drops of polyelectrolye to offset the strong electrostatic attractive forces between the submicron particles and made it into a free flowing liquid by applying a negative surface charge on the ZnO particles through the polyelectrolyte. Students learn that as the size of a sample decreases and approaches the nanoscale, chemical reactivity is enhanced and often materials will exhibit different properties that are unique and unexpected.

Size & Scale—In 6-8 grade, students are first introduced to an analogy of apples to atoms to get a feel for extreme dimensions. They imagine the size of an atom as big as an apple, then the actual apple would be expanded to be as big as the earth. Using interactive tools, they continue to explore large magnitude changes in object size and from extremely large to extremely small length scale, as well as different phenomena through time scale, heat scale, and gravity scale. Students are also challenged at the end to play a computer sorting game to sort various objects according to their scale or “world” (e.g. atomic, nano-, micro-, astronomical).

Size & Scale—In 9-12 grade, students consider additional factors relating to size and scale, such as powers of 10, scaling, ratio, and proportionality. Students cut strips of paper into lengths that differ by a factor of 10, starting from 10 meters down to the thickness of a strand of hair, and laid parallel to one another to deepen their awareness of these magnitude changes. Using their imagination, they continue the cutting process down to the nanometer scale. Students then apply proportional thinking and fix ratios to help relate nanoscale objects to macroscale objects to get a feeling of how small a nanoscale object is. For example, a carbon nanotube (1 nm in diameter) is scaled to the thickness of a human hair in the same proportion as a hair is scaled to a 10 meter school bus. Students are challenged to scale themselves to the scale of a globe of Earth and express Alice’s abnormally tall and abnormally short heights in Alice’s Adventures in Wonderland. Finally, they integrate this knowledge by creating a poster based on a theme/object of their interest. They breakdown an object and illustrate the various components it contains in appropriate scale: macro-, micro-, and nano-. For example, one could start with a tree > leaf > epidermis >plant cell > chloroplast > thylakoid membrane > chlorophyll > ATP.

SVR—In 6-8 grade, students begin by looking at two-dimensional (2-D) behavior. They create shapes with a constant number of identical sticks; thus all shapes have a constant boundary or perimeter. The goal for each shape is to minimize or maximize the perimeter-to-area ratio. Then students move on to 3-D behavior, working with a specific number of small cubes to either minimize or maximize the surface-to-volume ratio. Students find that the results of the 2-D behavior are analogous to those of 3D: the most compact shape, square or cube, yields the minimum P/A or S/V, and the maximum ratio is achieved by “stretching out” the shape. This knowledge permits a better understanding of the relationship between ambient temperatures with body size and shape of many familiar animals, such as Emperor penguins in the Antarctica and the much smaller Fairy penguins in Australia and New Zealand.

Below is a sample flowchart of the 6-8 SVR Activity: (click the picture to see flowchart details)

SVR—In 9-12 grade, students build on the 2-D and 3-D results and explore further the mathematical relationship between surface area-to-volume ratio as a function of size for fixed shape objects. They discover that, when shape is constant but volume changes, S/V is inversely proportional to size. Performing graphical analysis, students consider the implication of S/V data, especially the asymptotic behavior for very small lengths approaching the nanometer scale. Thus when an object is so small, a large fraction of its atoms are surface atoms, which are responsible for many of the special properties matter exhibited on the nanoscale. For example, macroscale and microscale gold are very inert, but when it is down to a few nanometer in size it becomes an extremely good catalyst for certain chemical reactions. Many other applications benefit from their vastly increased surface area and small size at the nanoscale, such as enhanced catalytic activity of existing catalysts, increased strength and toughness of metal and ceramics, greater capacity for energy storage in batteries and fuel cells, and higher absorbency for air and water filters in ultrahigh purity applications.

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