UNIT OVERVIEW

Why does water form droplets on a leaf instead of spreading flat? Why do some liquids evaporate quickly while others take much longer? The answers lie in intermolecular forces — the attractions between molecules that determine physical properties you can observe.

In previous work, you learned how atoms bond together to form molecules through intramolecular forces (covalent, ionic, and metallic bonds). Now we examine what happens between those molecules. These forces are weaker than chemical bonds, but they are essential for life. Without intermolecular forces, water would not be liquid at room temperature!

What You Will Learn

• The difference between intramolecular and intermolecular forces
• How to identify and compare three main types of intermolecular forces: ion-dipole, dipole-dipole (including hydrogen bonds), and London forces
• Why polar and non-polar molecules behave differently
• How intermolecular forces determine boiling points, melting points, surface tension, solubility, and capillarity
• The unique properties of water and how they relate to its molecular structure
• How to predict physical properties based on molecular structure