- is the [[Heat|Heat Energy]] *per* [[Atom|Atom]] - you can have an object with enormous [[Heat|Heat Energy]] (i.e Pacific Ocean), but very low temperature (i.e you skinny dip in ocean you'll freeze) - measured by a thermometer - [[Fahrenheit]] used in the US - [[H20]] freezes at 32 deg, boils at 212 deg - Stahler mentions we are unusual for using [[Fahrenheit]] - [[Celsius]] used in Europe - [[H20]] freezes at 0 deg, boils at 100 deg - [[Kelvin]] is a much more fundamental system, more important in [[⚛️ PHYSICS]] - [[Kelvin]] = [[Celsius]] + 273 - at 0 deg [[Kelvin]], *all* random motion stops, **you can't go lower** - you can also never get to absolute 0 - higher temperature generally causes solids to expand - (which is why sidewalks have slits, to let hot sidewalks fill that in) - colder temps cause contraction http://www.infocobuild.com/education/audio-video-courses/physics/Physics10-Spring2015-Berkeley/lecture-03.html