Molecular model of matter

We have to refine our atomic and molecular model of matter to see how bulk properties can be interpreted in terms of the properties of individual molecules, such as their size, shape, and polarity. We begin by exploring intermolecular forces, the forces between molecules, as distinct from the forces responsible for the formation of chemical bonds between atoms. Then we consider how intermolecular forces determine the physical properties of liquids and the structures and physical properties of solids. 

Our understanding of the energy of molecules is based on a molecular model of matter that assumes that all matter is in constant motion. This idea may seem a bit implausible at first, given that there are ample observations in our everyday experience that tell us some materials are solid, stable, and immobile. It is a bit difficult to acknowledge that at the molecular level a cement sidewalk is actually wriggling around like a can of anxious worms, but it is. The model of molecules in motion works well for explaining why gases and liquids behave as they do and still allows cement to behave the way it does. 

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