* Constant: Molecules are never truly still, even in solids. They vibrate and move around.

* Random: The direction and speed of their movement is unpredictable.

The degree of molecular motion depends on the state of matter:

* Solids: Molecules are tightly packed and vibrate in place.

* Liquids: Molecules are less tightly packed and can move around more freely.

* Gases: Molecules are far apart and move rapidly in all directions.

This molecular motion is responsible for many physical properties of matter, including:

* Temperature: Higher temperatures mean faster molecular motion.

* Pressure: Gas pressure arises from molecules colliding with the walls of their container.

* Diffusion: Molecules spread out from areas of high concentration to areas of low concentration.

* Heat transfer: Heat is transferred through the collision of molecules.

Key Concept: The Kinetic Molecular Theory describes the relationship between molecular motion and the properties of matter.