Intermolecular Forces (SAM)

Interactive, scaffolded model

Overview and Learning Objectives

This unit focuses on the attractive forces felt between molecules. Both London Dispersion and Dipole‐Dipole intermolecular attractions will be discussed with emphasis on factors such as polarity and surface area as defining factors in how strong the intermolecular attractions will be and the affect this has on the properties of materials.

Students will be able to:

• Describe the difference between the kinds of molecules attracted via London Dispersion attractions and Dipole‐Dipole attractions.

• Indicate which type of intermolecular attraction is generally stronger

• Describe two factors that affect the strength of intermolecular attractions.

• Determine which substance would have the highest boiling point based upon its molecular structure.

• Explain why oil and water donʹt mix.

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Classroom Practice

Teacher's Guide:

http://sam.concord.org/publications/teacher-guides/vdwTecherGuide.ver4.pdf

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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

Fermi Lab's ARISE Project suggests the following enhancement to this SAM unit: http://www.concord.org/~barbara/SAM/ARISE/ARISE_SAM_intermolecular.pdf

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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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