Gases
Lowest density, highest energy form
Individual molecules or atoms in a gas are disordered, i.e. they fly about in "empty" space, independent of each other
- So independent are the individual molecules in gases that highly compressed gases still behave like gases
Molecules or atoms collide with other atoms or molecules or the walls of our container, producing a measurable pressure
- Raising the temperature (i.e. adding energy to gas) causes the pressure to increase
Condensing vapors shrink by a factor of about 1000; i.e. the volume of the liquid is ~ 1/1000th the volume of the gas
Condensing vapors give off heat (²H of condensation), even though the temperature remains constant
Condensed phase, a liquid, has lower internal energy than the corresponding gas