Chapter 3
Phases/States of Matter
3.1 Solids, Liquids, and Gases
–How materials are classified
–Phases are based on amount of heat energy
This determines shape, volume, and density
–There are 5 phases of matter
Solids
 Definite shape and definite volume
Atoms are very tightly packed
Atoms are moving slowly
Lower amount of heat energy than liquids, gases, plasma
Liquids
Definite volume but no definite shape
Takes shape of the container
Atoms are farther apart and move more than solids and BEC’s
Liquids have less heat energy than the gas and plasma phases
Gases
No definite shape and no definite volume
Gases take shape and volume of container (gases take up all the available space in a
container because their atoms move a lot)
Atoms are very far apart
Atoms move more than in solids or liquids
States of Matter
Other states of matter
Plasma
– extremely high temperatures
– sun and stars
- most heat energy of the 5 phases
- “SUPER GAS”
Bose-Einstein condensate (BEC)
– extremely low temperatures
Temp. near absolute zero, -273 °C
– atoms act as a single particle
- least amount of heat energy of the 5 phases
- “SUPER SOLID”
Kinetic Theory
All particles of matter are in
constant motion
Kinetic Energy – energy an
Faster an object moves – the
object has due to its motion
greater its kinetic energy is
Behavior of Gases
Kinetic Theory of Gases
–Particles are in constant, random motion
–Motion of one particle is unaffected unless particles collide
–Forces of attraction among particles in a gas can be ignored under ordinary conditions
Behavior of Liquids
Attraction between particles do affect their movement
Liquid takes shape of container because particles can flow
Volume is constant because forces of attraction keep particles closer together than
gases
Behavior of Solids
Atoms have “fixed” locations
Definite shape and volume because particles vibrate around fixed locations
Atoms do not exchange places with neighboring atoms
Sec. 3.2 The Gas Laws
Pressure – the result of a force distributed over an area
Collisions between particles of a gas and the walls of the container cause pressure.
Factors that Affect Gas Pressure
Temperature
 temperature =  pressure
 temperature =  pressure
Volume – changing volume affects pressure - indirectly
 volume =  pressure
 volume =  pressure
Number of Particles – affects pressure directly
 # particles =  pressure
 # particles =  pressure
Charles’s Law
States that the volume of a gas is directly proportional to its temperature in kelvins
Direct relationship
As temperature  = volume 
As temperature  = volume 
Boyle’s Law
States that the volume of a gas is inversely proportional to its pressure
Indirect relationship
As volume  = pressure 
As volume  = pressure 
Sec. 3.3 Phase Changes
Phase change – when a substance changes from one state to another
a reversible physical change
Six common phase changes – melting, freezing, vaporization, condensation,
sublimation, and deposition
Energy and Phase changes
•During phase change – energy is transferred between substance and surroundings
•Energy is either absorbed or released by the substance
•HEAT ENERGY DRIVES ALL PHASE CHANGES!!!
Endothermic change – substance absorbs energy from surroundings
melting
vaporiztion
sublimation
Exothermic change – substance releases energy to its surroundings
freezing
condensation
deposition
Melting and Freezing
Melting: Solid  Liquid
Melting point – temperature at which melting occurs
Water 0°C or 32°F
Freezing: Liquid  Solid
Freezing point – temperature at which freezing occurs
Melting points and freezing points are the same for a given substance
Different substances have different melting & freezing points
Vaporization and Condensation
Vaporization – Liquid  Gas
Endothermic process – absorbs heat energy
Two types – evaporation and boiling
Evaporation – takes place on the surface and at temperatures below boiling point
Boiling – vapor pressure = atmospheric pressure: adding lots of heat
Water boils at 100°C or 212°F
Condensation – Gas  Liquid
–Exothermic process – heat energy is released
–Ex. bathroom mirror after a shower, morning dew
Sublimation – Solid  Gas
–Endothermic process – heat energy is absorbed
–Ex. Dry ice CO2
 Deposition –
Gas  Solid
oExothermic process – heat energy is released
oOpposite of Sublimation
o
Ex. Carbon dioxide – CO2