Intermolecular Forces

Intermolecular forces are the forces of attraction or repulsion between molecules. These forces play a crucial role in determining the physical properties of substances such as melting and boiling points, viscosity, and solubility.

Types of Intermolecular Forces

There are three main types of intermolecular forces:

• London Dispersion Forces: These forces are the weakest type of intermolecular forces and exist between all molecules. They occur due to temporary fluctuations in electron distribution, creating temporary dipoles.
• Dipole-Dipole Interactions: These forces occur between polar molecules with permanent dipoles. The positive end of one molecule is attracted to the negative end of another molecule.
• Hydrogen Bonding: Hydrogen bonding is a special type of dipole-dipole interaction that occurs when hydrogen is bonded to highly electronegative atoms such as oxygen, nitrogen, or fluorine. This results in a particularly strong dipole-dipole interaction.

Effects of Intermolecular Forces

Intermolecular forces influence several important properties of substances:

• Melting and Boiling Points: Substances with stronger intermolecular forces generally have higher melting and boiling points because more energy is required to overcome these forces.
• Viscosity: Substances with stronger intermolecular forces tend to have higher viscosities, as the molecules are more strongly attracted to each other and move more sluggishly.
• Solubility: Intermolecular forces also affect a substance's solubility in a particular solvent. Like dissolves like – polar substances tend to be soluble in polar solvents due to favorable intermolecular interactions.

Study Guide

To understand intermolecular forces, it's important to:

1. Learn about the different types of intermolecular forces and how they arise.
2. Understand the relationship between intermolecular forces and physical properties such as boiling and melting points, viscosity, and solubility.
3. Practice identifying the types of intermolecular forces present in different substances.
4. Study examples of substances with different intermolecular forces and predict their behaviors based on these forces.

[Intermolecular Forces] Related Worksheets and Study Guides:

• Solids, liquids and gasesScience • Sixth Grade