Change of Phases
Phase Changes include:
- evaporation- liquid to gas and occurs at the surface of a liquid
- boiling- liquid to gas; difference between evaporation and boiling is boiling can occur anywhere in the liquid
- boiling point- a temperature at which a liquid boils
- pressure affects the boiling point: increase pressure = increase in boiling point and decrease pressure = decrease in boiling point
- condensation- gas to a liquid; warming process
- freezing- liquid to solid; when kinetic energy is low and the energy of the attraction is greater
- melting- solid to liquid; when the kinetic energy is high enough to the energy of the attraction
- sublimation/deposition- solid to gas without passing through the liquid phase
- the temperature of a substance is related to the average kinetic energy of the particles
- if there is enough kinetic energy in a particle, the particle can go into the atmosphere
- lower kinetic energy = lower temperature
- when there is more evaporation than condensation, the volume and the temperature decrease
- when there is an equal amount, the volume and the temperature stay the same
- when there is more condensation than evaporation, the volume and the temperature increase
Fog and Clouds
- warm air rises and expands
- when the air expands, it chills and the water molecules slow down and stick together forming clouds and fog
- Bubbles in liquid can only form when the pressure of the vapor within the bubbles is great enough to resist the pressure of the liquid
Heat of Fusion
- the amount of energy/mol needed to convert between solid and liquid
- H2O = 6 kJ/mol
Heat of Vaporization
- amount of energy/mol that is needed to convert between a liquid and a gas
- H2O = 41 kJ/mol
Intermolecular Forces
- forces between molecules
- dipole-dipole
- hydrogen bonding
- London dispersion forces
Dipole-Dipole
- decimal because it only has a partial charge
- weak attraction
- electrons move slightly closer to one side
Hydrogen Bonding
- bonding with hydrogen
- permanent
- electronegativity
London Dispersion
- compounds that don't have partially negative charges but can acquire them
*all three deal with positive and negative bonding
Intra- inside
Inter- between
Crystalline Solids
Ionic- stable, high melting points
Molecular- low melting points
Atomic-
alloy- a metal with a nonmetal added to it
2 types of alloys:
substitutional- sub out/replace molecules
interstitial- put molecules between spaces
Intra- inside
Inter- between
Crystalline Solids
Ionic- stable, high melting points
- ex: NaCl
Molecular- low melting points
- ex: ice
Atomic-
- ex: diamonds
alloy- a metal with a nonmetal added to it
2 types of alloys:
substitutional- sub out/replace molecules
- ex: brass
interstitial- put molecules between spaces
- ex: steel