Active Filters (demo)

Overview and Learning Objectives

This is a model of two ways to filter a toxin out of the air. The purple molecules make up an active filter -- they have a strong, specific attraction to the toxin. The concentration of the toxin in the air declines as it sticks to the filter, then levels off as the filter saturates.

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Central Concepts

Key Concept:

Van der Waals forces are weak, but sufficient to make things adsorb to a surface. A more complex surface area can absorb more molecules.

Additional Related Concepts

Physics/Chemistry

• Absorption

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Benchmarks and Standards

AAAS

• COMMON THEMES: Models - The usefulness of a model can be tested by comparing its predictions to actual observations in the real world (Full Text of Standard)
  
  

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Additional Info

Additional Background

The two models are identical, except for the arrangement of the molecules in the filter. As the models run, you can see that one of the filters gets more of the toxin out of the air, because it has a higher surface area. In the real world, activated charcoal is a good filter of this type because it has an enormous surface area (it's full of tiny pores). The charcoal doesn't really need a specific attraction to whatever impurities it's filtering -- that was just used in this model to make it work. Apparently, van der Waal forces and hydrogen bonds are sufficient to make things adsorb to it. Activated charcoal is used in things like gas masks, Brita water filters, and even for removing caffeine from coffee.

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Activity Credits

Created by CC Project: Molecular Workbench using Molecular Workbench

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Requirements

• Java 1.5+ - Java 1.5+ is available for Windows, Linux, and Mac OS X 10.4 and greater. If you are using Mac OS X 10.3, you can download MW Version 1.3 and explore within it instead.

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