refers to irregular motion of smoke in air or pollen in water
Einstein explanation for the motion as
caused by bombardment of air particles.
Bigger visible particles are under continuous bombardment by smaller
invisible particles and are kept in continuous random motion
Kinetic model of matter
kinetic ==> moving
States that all matter is made of tiny particles in continuous motion
Comparing different states of matter
Solid
Physical properties: Incompressible,
fixed shape and volume
Molecules are packed closely
Strong intermolecular force
Motion of particles: Vibrate about fixed
positions
Liquid
Incompressible,
fixed volume, takes
shape of vessel
Packed closely
Some attractive forces
Free to move within vessel
Gas
Compressible,
no fixed shape or
volume
Far apart
Little attractive forces
Free to move at high speeds
Temperature of matter is related to kinetic
enegy possessed by the particles
In ascending order, solids, liquids, gases
Note: phase change is related to potential energy
In general, matter in solid state
have the least spacing, followed
by liquid and gas.
Exception: Water has a greater
spacing in solid than in liquid state,
minimum spacing at 4 degree celcius
Gas Laws
Boyle's
p is inversely
proportionate to V,
p1V1=p2V2
Explained using KMM: For gas compressed slowly (same temperature), the
frequency of the gas particles bouncing off the surface of the vessel increases
due to reduced volume, causing an increase in pressure in gas
T is the constant
Charles's
V is proportionate to T
For gas in an insulated (temperature allowed to increase) vessel with a frictionless (same
pressure) piston, temperature increase results in the average speed of particles to increase,
which will increase force of collision on the piston, pushing the piston outwards until gas
pressure is the smae as pressure in the surroundings.
p is the constant
Gay-Lussac's
p is proportionate to T
For gas kept in an insulated vessel (same volume) temperature increase results in the average
speed of particles to increase. This in turn increases both the frequency of the gas particles
bouncing off the surface, and the force of collisions, causing an increase in pressure of gas.
V is the constant
Summary
Brownian motion demonstrates moving
nature of gas/liquid particles.
Kinetic model: particles are in constant motion, temperature
of substance is related to motion of particles