When an ionic substance or highly polar compound dissolves in
water, water molecules orient themselves around the ions or polar compound,
hydrating the species. In the solution process the hydration that occurs around
the ion or polar compound involves ion-dipole or dipole-dipole bond fomation.
While these interactions are weak, they are strong enough that the solution
process is generally accomplished with a gain (exothermic) or loss (endothermic)
of energy. The details of the parameters which govern the energy of the solution
process involve a knowledge of the solute-solute attractive forces, the solvent-solvent
attractive forces and the solute-solvent attractive forces.
View the movie of the dissolution of NaCl in water.
1. What color are the sodium ions, Na+, and the chloride ions, Cl-, in the video? Answer
2. What are the attractions that try to keep the sodium ions and chloride ions in the solid phase? Answer
3. What are the attractive forces between the ions and the water molecules? Answer
The movie you are looking at was captured from a simulation available at concord.org. The link Concord.org animation of dissolution of NaCl in water is http://mw.concord.org/modeler/showcase/simulation.html?s=http://mw2.concord.org/public/student/solution/dissolve.html . This link will run in Safari 11, but not in Safari 12. It will also run in Windows 10.