Van der Waals Attractions (SAM)

Interactive, scaffolded model

Overview and Learning Objectives

Students learn about weak attractive forces between molecules, compare them to strong bonds, explore the strengths of the weak forces and determine the importance of surface area as it relates to the weak forces. They look specifically at hydrogen bonds and the importance of charge as it relates to the weak forces. Finally, they are challenged to design their own models of molecules that are attracted to each other.

Students will be able to:

• describe how weak electrostatic and van der Waals forces are capable of holding molecules in position;
• compare weak attractive forces between molecules to strong bonds;
• explore the strengths of the weak forces and determine the importance of surface area as it relates to the weak forces;
• explore hydrogen bonds and the importance of charge as it relates to the weak forces.

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Classroom Practice

This activity explores the variety of weak attractions between molecules, including polar and non-polar attractions and hydrogen bonds.

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Central Concepts

Key Concept:

The molecular world is sticky. Weak electrostatic and van der Waals forces hold molecules in position.

Additional Related Concepts

Concept Map Available

Molecular Biology

• Self-assembly

Physics/Chemistry

• Hydrogen bonds
• Solubility
• Van der Waals

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Textbook References

• BSCS Blue (8th Edition) - Chapter 1: The Chemistry of Life

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Benchmarks and Standards

AAAS

• THE PHYSICAL SETTING: FORCES OF NATURE - Electromagnetic forces acting within and between atoms are vastly stronger than the gravitational forces acting between the atoms (Full Text of Standard)
  
  

NSES

• Physical-Science: Motions and Forces - 4 Between any two charged particles, electric force is vastly greater than the gravitational force (Full Text of Standard)
  
  

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Extensions and Connections

An interesting extension is the employment of weak forces in filters such as Active Filters: http://molo.concord.org/database/activities/239.html

Another extension is Distillation and the Role of Weak Forces: http://molo.concord.org/database/activities/274.html

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Additional Info

Additional Questions

The water from the well that supplies your house is running brown -- there are lots of polluting particles in it. How would you set up a system to get clear water?

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Activity Credits

Created by CC Project: SAM 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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