Hydrogen bonds
Recall: molecules such as water (H2O) possess partial charges on their atoms. Electrostatic attraction between the partial negative charge (δ-) on the oxygen of one water molecule and the partial positive charges (δ+) on the hydrogens of another water molecule will be weakly attracted to one another. These interactions are relatively weak because the charges on the atoms are only partial charges. These weak intermolecular interactions that hold polar molecules together are called hydrogen bonds.
We will explore the remarkable properties of water in the next chapter.