thermal physics - brownian motion

kinetic molecilar theory

all matter is made of particle, which are constantly in motion

postulates

• all matter consists of atoms

• atoms join together to form molecules]solids keep shape and volume

• liquids keep volume but not shape

• gas keeps neither

• molecule motion is random

• it is greatest in gas, then liquid, then solid

• collisions between atoms and molecules transfer energy between them

• molecules in motion have KE

• molecules in gases do not exert large forces on each other unless they are colliding

brownian motion

• 1827

• botanist robert brown

• he noticed that tiny partivles of pollen suspeneded in water moved with a zigzag, random motion

• this type of movement of any particle suspended in a fluid is known as brownian motion

cause of brownian motion

• einstein showed that the motion provided evidence for teh existence of atoms or molecules in teh water - the kinetic model of matter

• the randomly moving water particles were hittting teh pollen particles unevenly, causing this motion.