Kinetic Theory of Matter (KTM) AKA: Kinetic Molecular Theory (KMT) Molecular Kinetic Theory (MKT) Not associated with TKM—the international postal code for Turkmenistan
Rule 1 • All matter is composed of particles in constant motion
Rule 2 • Temperature is a measure of the kinetic energy of the particles.
Rule 2 (a and b) • Temperature is a measure of the kinetic energy of the particles. a) When you heat a sample, the particles speed up b) When you cool a sample the particles slow down
After that, things get hazy. ?
Consider the state: • Solid Liquid Gas
Particles in motion: • Solid Liquid Gas
Particles in motion: • Solid Liquid Gas Vibrating about a fixed position
Particles in motion: • Solid Liquid Gas Moving over and around other particles, unlikely to escape surface
Particles in motion: • Solid Liquid Gas Moving freely, colliding with other particles and the walls of container
Consider state changes: Gas Sublimation Solid Melting Condensation Freezing Boiling, evaporation, vaporization Liquid
Particles on particles: • Solid Liquid Gas Particles in contact Particles in contact Particles not touching
This is huge. Really.
Values and preferred units • P—atmospheres • T—kelvins • V—Liters • n—moles
Conversions • P: 1 atm =760 mmHg=760torr =101.3 kPa=101,325 Pa • T: T(k) = T(oC) + 273 • V: 1L=1000 ml=.001 m3
How fast do particles move? It depends on:
How fast do particles move? It depends on: • Temperature: • Size of the particle:
How fast do particles move? It depends on: • Temperature: High T faster motion • Size of the particle: Smaller faster
Cool, medium, warm
Phase diagrams What about water? P 1 atm 0 atm T 0 k 273 k 373 k
Phase diagrams What about water? Water melts / freezes Water boils/ condenses P 1 atm 0 atm T 0 k 273 k 373 k
Phase diagrams What about water? P Water is a solid Water is a liquid Water is a gas 1 atm 0 atm T 0 k 273 k 373 k
Phase diagrams What about water? Increasing pressure will melt ice Decreasing pressure will boil water P Water is a liquid Water is a solid Water is a gas 1 atm 0 atm T 0 k 273 k 373 k
Phase diagrams What about water? P Water is a liquid Water is a solid Water is a gas 1 atm Sublimation occurs at low T and P 0 atm T 0 k 273 k 373 k
Phase diagrams What about water? P Water is a liquid Water is a solid Water is a gas 1 atm 0 atm T 0 k 273 k 373 k
Phase diagrams Describe these processes Water is a liquid A B H P Water is a solid C I G 1 atm E Water is a gas D F 0 atm T 0 k 273 k 373 k
Phase diagrams Describe these processes P Heating curve lab 1 atm Vacuum pump demo 0 atm T 0 k 273 k 373 k
Phase diagrams Water P Normal melting point 1 atm Normal boiling point Triple point 0 atm T 0 k 273 k 373 k
Phase diagrams Water P 1 atm Critical pressure 0 atm T 0 k 273 k 373 k
Phase diagrams Most other substances P Critical pressure Critical temperature 0 atm T 0 k
The phase diagram for water
Phase diagrams 1 atm P 0 atm T 0 k
Phase diagrams 1 atm P Critical pressure Critical temperature 0 atm T 0 k
The phase diagram for CO2
The phase diagram for water
Can you explain why each of these phenomena occurs? Thermal expansion of a solid—solids expand when heated Thermal expansion of a liquid –liquids expand when heated Thermal expansion of a gas –gasses expand when heated
Can you explain why each of these phenomena occurs? Compressibility of gasses—gasses can be compressed into a smaller volume Incompressibility of liquids –liquids can’t be compressed into a smaller volume Incompressibility of solids –solids can’t be compressed into a smaller volume
Can you explain why each of these phenomena occurs? Conduction of heat between two objects in contact—the cool one warms up. Heat flow stops when temperatures are equal
Can you explain why each of these phenomena occurs? Fluidity of gasses—gasses flow, they have no fixed shape Fluidity of liquids—liquids flow, they have no fixed shape Rigidity of solids—solids do not flow, they have a fixed shape
Can you explain why each of these phenomena occurs? Melting point of a solid —at a certain temperature, a solid changes into a liquid Boiling point of a liquid —at a certain temperature, a liquid changes into a gas Freezing point of liquids –at a certain temperature, a liquid changes into a solid Melting is endothermic (requires heat) Boiling is endothermic (requires heat)
Can you explain why each of these phenomena occurs? Liquification of gasses is accomplished at low temperatures and high pressures Sublimation of solids (to gas) at low pressures Sublimation of solids (to gas) at high temperatures Evaporation cools a liquid You can see your breath on a cold day
Can you explain why each of these phenomena occurs? Boyle’s Law —when the volume of a gas is reduced, its pressure increases Charles’ Law —when gasses are cooled, their volumes act as if they will reach zero volume at a temperature of absolute zero Avogadro’s Law —identical volumes of gasses contain the same number of particles Graham’s law —heavier gasses diffuse slower Dalton’s law of partial pressures —the total pressure of a mixture of gasses is the sum of the pressures of each gas.
Can you explain why each of these phenomena occurs? Decrease in boiling point of a liquid with lower pressure Increase in boiling point when solutes are added to a solvent Decrease in freezing point when solutes are added to a solvent Metals conduct heat better than other solids
