Exploring Ionic Compounds

Interactive, scaffolded model

Overview and Learning Objectives

In this model-based activity, students will learn the main concepts behind the process of dissolving. They begin by discovering the properties of ionic and polar compounds and observe that in order to be water-soluble, molecules should carry an electrical charge.

Working with models, students compare the solubility between ionic compounds such as table salt, polar organic molecules such as glucose, and non-polar organic molecules such as oil. They observe how water molecules attract ionic or polar substances, leading to the dissolving of various materials, and how non-polar molecules are pushed out by water, "preferring" to stick to each other.

Students will be able to:

• describe how the presence or absence of electrical charge (positive, negative, polar, or neutral) affects whether a substance will be dissolved by water;
• explain that on the microscopic level dissolving includes three simultaneously occurring dynamic processes: interactions between water molecules, interactions between particles of the substance, and interactions between those particles and water;
• reason that for dissolving to occur, the interactions between molecules of the substances with water molecules must be stronger than their attraction to each other.

return to top

Assessment

1a. What happens to salt on an atomic level (include molecules and ions in your description) when it dissolves in water? Describe the way in which the salt and the water interact.

1b. Alcohol is slightly polar. What happens to salt on an atomic level when it is placed in alcohol?

1c. Draw a picture that shows a salt solution in water. Be sure to label your picture or provide a key for any symbol you use.

1d. Draw a picture that shows a salt solution in alcohol. Be sure to label your picture or provide a key for any symbol you use.

return to top

Classroom Practice

http://www.concord.org/~barbara/workbench_web/unitIII_mini/act_sol_solutions.html

return to top

Central Concepts

Key Concept:

Water is a great solvent, but all substances that water can dissolve must be either polar or ionic (either positively or negatively charged). The polar water molecules attract charged particles and push out non-charged particles. Water is attracted to itself, to other polar molecules, ionic substances, and to non-polar substances.

Additional Related Concepts

Molecular Biology

• Polar molecules
• Polar nature of water

Physics/Chemistry

• Charge
• Concentration
• Dissolving
• Ionic bonds
• Molecule
• Salt
• Solubility
• Solutions

return to top

Textbook References

• Biology (Miller and Levine) Prentice Hall 5th Edition - Unit 1: Chapter 4 - The Chemical Basis of Life
• Biology: Concepts and Connections (Pearson) 5th Ed. - Chapter 3: The Molecules of Cells
• Biology: Concepts and Connections (Pearson) 5th Edition - Chapter 2: The Chemical Basis of Life
• Biology: Exploring Life - Chapter 4: The Chemical Basis of Life
• Biology: Exploring Life - Chapter 5: The Molecules of Life
• Biology: The Dynamics of Life - Chapter 6: The Chemistry of Life
• BSCS Blue (8th Edition) - Chapter 1: The Chemistry of Life
• Web of Life - Chapter 2: Chemical Basis of Life

return to top

Benchmarks and Standards

NSES

• Physical-Science: Matter Structure/Properties - 4 The physical properties of compounds reflect the nature of the interactions (Full Text of Standard)
  
  

return to top

Extensions and Connections

http://www.concord.org/~barbara/workbench_web/unitIII_mini/ext_solutions.html

return to top

Activity Credits

Created by CC Project: Molecular Workbench using Molecular Workbench + Pedagogica

return to top

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.

return to top