1. The Kinetic Theory
2. Bernoulli’s Billiard Balls
a. Attempted to model behavior of molecules
b. Properties required of model
i. Elastic collisions (no loss of energy)
ii. Random motion in straight lines
c. Billiard balls have those properties
3. Maxwell develops kinetic theory
a. Theory has 4 principles
b. Describes molecules in a substance
c. Can explain states matter and phase changes
d. Can explain the behavior of gases and plasmas
4. Principle 1
a. All matter is made of small particles
b. Atoms, ions, molecules
c. Number of particles (moles) key, not mass
5. Principle 2
a. Particles are in constant motion
b. Speed is determined by energy level (temperature)
c. Motion is in straight line until collision
d. Motion is random, no preferred direction
6. Principle 3
a. Collisions are elastic
b. Energy is conserved
c. Transferred from high to low energy particle
7. Principle 4
a. Cohesive forces exist between particles
i. A force between like particles
b. Level of cohesive force determines the state of matter
8. Pressure
a. Result of collision of particles with wall of container
b. Each collision transfers energy to container from particle
c. Pressure is total energy transferred by all collisions
9. Pressure
a. Increasing number of collisions increases the pressure
b. Standard pressure is 101.325 kPa (1 atm)
10. Calculation of pressure
a. Manometers (barometers) measure in mm of Hg
b. Pressure raises level of Hg
c. 1 kPa = 7.501 mm Hg
d. Divide change in height by 7.501 to find pressure in kPa
11. Temperature and Energy
a. Particles in motion have KE
b. Unable to measure KE directly
c. Temperature is measure of average KE
d. Temperature directly related to particle velocity
12. Temperature and Energy
a. Particles of more massive substance move slower at same temperature
b. Energy moves from high to low temperature
13. Measurement of Temperature
a. Kelvin scale is standard
b. Based on property of all matter, point of zero KE
c. Measures average KE
d. Device converts measurement to temperature
e. K = C + 273
14. States of Matter
a. Solid
b. Glass
c. Liquid
d. Gas
e. Plasma
15. Solid
a. Particles held closely by cohesive forces
b. Particles held in 3-dimensional pattern (crystal)
c. Motion: straight-line vibration
d. Have definite shape and volume
e. Tend to have ionic bonds or molecules of high mass
16. Glass
a. Particles held closely by cohesive forces
b. Material cools too quickly for pattern to form
c. Plastic rather than liquid during transition
d. Motion: vibrations
17. Glass (cont)
a. Have definite shape and volume
b. Heat capacity of liquid determines rate of entropy loss
c. Slow entropy loss forms glass
18. Liquid
a. Particles loosely held by cohesive forces
b. Particles slide by each other
c. Have a definite volume but take shape of container
d. Tend to be polar molecules or molecules of medium mass
19. Liquid Crystals
a. Structure in 1 dimension
b. Structure changes with electric or magnetic field
20. Gas
a. No cohesive forces hold particles
b. Particles move independent of each other
c. Direction changes only with collision
d. Assume shape and volume of container
e. Tend to be nonpolar molecules or have low mass
21. Plasma
a. Heated to high temperature >5000K
b. Collisions knock atoms apart
c. Mixture of electrons and positive ions
d. Most common state of matter in universe
22. Plasma (cont)
a. Shares properties A to D of gasses
b. Acts as conducting fluid, generates magnetic field
c. Affected by magnetic and electric fields
23. Phase Changes
a. Change in structure w/o change in composition
b. Combination of energy and pressure determines change point
c. Direct relationship with energy (temperature)
d. Direct relationship with pressure
24. Latent Heat
a. Energy gained or lost in phase change
b. Hf: (fusion) energy of freezing or melting
c. HL:(vaporization) energy of boiling, evaporation, condensation
d. Hs: (sublimation) energy of sublimation
25. Evaporation
a. Change to gas at surface of liquid
b. Surface tension and atmospheric pressure hold molecules
c. Collisions transfer energy between particles
26. Evaporation
a. Molecules gain energy to overcome PE of cohesive force
b. Molecules leave surface 1 at a time
c. Rate dependent on suface area, KE, humidity
27. Condensation
a. Change from gas to a liquid
b. Molecules transfer energy and slow down
c. PE of cohesive force greater than KE liquid forms
d. Heat released to environment
28. Equilibrium
a. Both processes occur at same time
b. At particular temperature, pressure and humidity both happen at same rate
29. Sublimation
a. Change from solid to gas
b. Below triple point
i. May exist as solid, liquid, gas
ii. Depends on temperature and pressure
c. Process similar to evaporation
d. Vapor pressure greater than 1 atm
30. Boiling
a. Change from a liquid to a gas within the liquid
b. Energy added and molecules over come Vapor Pressure
i. Air pressure and,
ii. PE of cohesive force
c. Large number of molecules change state at once
31. Freezing
a. Change from a liquid to a gas
b. Energy removed from material
c. PE of cohesive force > KE of molecules
d. Molecules pulled into lattice
32. Phase Change Diagram (H2O)
a. Below 0ºC temperature increases
b. At 0ºC PE of cohesive force overcome
c. 0ºC to 100ºC temperature increases
d. At 100ºC PE of cohesive force overcome
e. Above 100ºC temperature increase
33. Effects of Strong Cohesive Force
a. Nonvolatile
b. High boiling point
c. Low evaporation rate
d. High critical temperature
e. Low vapor pressure
34. Effects of Weak Cohesive Force
a. Volatile
b. Low boiling point
c. High evaporation rate
d. Low critical temperature
e. High vapor pressure
35. Le Chatelier’s Principle
a. All phases in equilibrium
b. Stress applied to system in equilibrium will cause system to change to reduce stress
c. Phase changes reduce stress on system
36. Sources of stress
a. Temperature
b. Pressure
c. Concentration
d. External forces
37. Skating example
a. Water expands as it freezes
b. Pressure of skate blade compresses ice
c. Water liquefies to release stress
d. Friction warms blades (stress)
e. Heat transferred to ice to relieve stress and ice melts