Intermolecular Attractions, Phases and Phase Changes

Intermolecular Attractions

Intermolecular attractions (also known as intermolecular attractive forces, IMAF's or IMF's) are those attractions that hold separate particles together in a solid or liquid. 

They are NOT the bonds that hold individual molecules together, but rather the forces that hold a group of molecules together. In other words, we are not talking about what holds two hydrogen atoms to one oxygen atom in a water molecule. That is bonding. 

Intermolecular Forces are the forces that cause lots of water molecules to stick together to form a drop. 

To understand intermolecular attractions you can picture all matter as composed of ions, polar molecules, non-polar molecules, or mixtures of those things.

In the diagram below, the three types of particles are listed at the corners of the triangle in black. In between those corners are mixtures that could be created from those three types of particles also listed in black. Below each of those particles of mixtures is the name of the attraction that exists between them, listed in blue. Lastly, there is an example listed in red.

Each of those forces in the triangle above must be understood:

• ion-ion attraction
• ion-dipole attraction
• ion-induced dipole attraction
• dipole-dipole attraction
• dipole-induced dipole attraction
• London Dispersion Force 

Of course, how strongly particles attract each other determines a great deal about their behavior including the phase of matter they are found in and how much energy is needed to cause a phase change.