1. 4.b Kinetic Molecular Theory

2. Kinetic Molecular Theory (KMT)
based on the idea that particles are constantly moving
can be applied to solid, liquid, or gas
Based on energy of particles and forces that act between them

3. KMT (cont’d) KMT of gases is a model of an ideal gas
Hypothetical gas that perfectly fits all the assumptions of the KMT
5 basic assumptions….

4. #1Gases consist of tiny particles that are very far apart
most volume is empty space-low density
allows gases to be easily compressed

5. # 2 All collisions between particles and container walls are elastic
there is no net loss of energy when particles collide
total KE stays constant  can be transferred between particles

6. # 3 Particles are in continuous, rapid, random motion
since they are moving, they have KE
KE overcomes their attractive forces

7. #4 No forces of attraction or repulsion
like billiard balls
bounce apart immediately

8. #5 Average KE depends on Temp
KE = ½mv2
where m = mass of particle
where v = velocity of particle
V, T, & KE are directly proportional
So…. KE ↑’s as T↑’s & V↑’s
at the same T, lighter particles have higher speeds than heavier ones

9. KMT and Nature of Gases Accounts for Physical Properties of gases….
Expansion – gases do not have a definite shape or definite volume
Assumption # 3 & 5
Fluidity – gas particles slide easily past one another
Both gases & liquids are knows as fluids
Assump #4

10. Physical Properties cont’d
Low Density – density of gas is typically 1/1000 the density of the same substance in the liquid of solid state
Compressibility – gas particles may be crowded close together since they are initially so far apart

11. Physical Properties cont’d
Gases spread out and mix with one another even without being stirred
Diffusion – spontaneous mixing of particles of 2 substances caused by random motion
Why smells spread out