11.4.13 - Intermolecular forces v. Intramolecular forces, and Water

Intermolecular Forces v. Intramolecular forces

This week, following out ionic and metal worksheets, we worked on understanding Intermolecular forces and intramolecular forces. Intermolecular forces are the forces between the molecules, while the intramolecular forces are between the actual atoms. For example, intermolecular forces hold together the H and O atoms in H2O, while the intermolecular forces hold together the molecules so that it stays together to form solids, liquids, or gas, depending on the temperature of the environment.

There are three types of intermolecular forces: induced dipole-induced dipole (London dispersion forces), Dipole-dipole, and Hydrogen bonding.

London dispersion force occurs between any two molecules because there is a momentary concentration of electrons on one side of the atom, causing a momentary dipole in the molecule. This is what holds molecules with no dipole moment. London dispersion force occurs in all molecules.

The next strongest intermolecular force is the dipole-dipole force. Molecules with this have attraction between the molecules due to the partial charges on the molecules from the dipole moment.

The strongest force is called the Hydrogen bond. This occurs between any molecule that has a Hydrogen atom bonded to either Nitrogen, Oxygen, of Florine atom.

To help learn the material, we went over two worksheets: Intermolecular Fores and Intermolecular Forces 1 Worksheet.

Water

We also went over a pogil about Water. We learned a little about why Salt (NaCl) dissolves in water. The hydrogen bonds override the ionic bond between the Na and Cl, breaking the ions apart. 

Main Ideas

This week, the main ideas connected because we need to know the characteristics of the intermolecular forces and intramolecular forces in order to understand why salt dissolves in water. The model with the molecules helped me because it was easy to understand which side attracted to which molecule. It also helped me understand why ice is less dense than liquid water, something I have been wondering for a very long time. I am becoming unsure, however, about the materials we covered in this weekend's lecture quizzes, "Liquids and Solids". I don't think I quite understand why liquids have surface tension.