Lesson 2: Solids and Liquids

In this lesson we will study the condensed phases of matter - the solid and the liquid phases.

In the gas phase the attraction between particles of gas is negligible - in fact, we assumed that it was zero. But in the condensed phases, those attractive forces are important, they bind the molecules (or atoms) together in the liquid and solid phases. Therefore, one of the things we will look at is the nature - and especially the relative strength - of the intermolecular forces in solids and liquids and try to relate their strength to some of the common properties: melting point, boiling point, surface tension, vapor pressure, and so on.

We will also learn to calculate the amount of energy that is needed to heat (or that is released on cooling) a solid or a liquid as well as the amount of energy involved in changing from a solid to a liquid and from a liquid to a gas. As you might suspect, the amount energy involved also depends on how strongly the particles are bound together as well as on how much of the material is involved.

Since intermolecular forces are essential to the topics covered in this Lesson, you should revisit Lesson 9 from CH 104, which can be found here: https://sites.google.com/view/ch104/ch-104-lesson-9. This lesson will assume that you are familiar with the three types of intermolecular force and how relatively strong each type is. It will further assume that you can use a formula or Lewis structure to quickly determine what type of IMFs a given compound will experience.