States of Matter / IMF

Question 1

Heating Curve

Answer 1

Shows changes in phase as heat is added and temperature increases

Question 2

Calculating Heat in Temp. Change

Answer 2

Q = mCpAT

Question 3

Calculating Heat Solid to Liquid

Answer 3

Q = mHf

Question 4

Calculating Heat Liquid to Gas

Answer 4

Q = mHv

Question 5

Intermolecular Forces (IMF)

Answer 5

Gasses don’t have IMFs
Gasses are made by breaking IMF
Three types of IMF : London Dispersion, Dipole-Dipole, Hydrogen Bond Forces (AKA “Hydrogen Bonds”)
Forces between molecules (covalent compounds)
IMF holds liquids and solids together (gives liquids and solids definite volume, and holds together the particles)

Question 6

Evaporation

Answer 6

Breaks IMF
Only happens at the surface of a liquid
Occurs at any temp. even cold ones
Evaporation is a COOLING process

Question 7

London Dispersion Forces

Answer 7

Weakest of the IMF types
Temporary
Form from nonpolar (pure) molecules
Break down easily, evaporate easily
Become gasses at room temp. (Ex. liquid nitrogen)
Are solids and liquids at cold temps.
All diatomics are held together by this IMF force

Question 8

Dipole-Dipole Forces

Answer 8

Medium strength IMF force
Forms from polar molecules
Liquids at room temp.
Alcohols typically have this IMF force

diPOL = POLar

Question 9

Nonpolar (pure) Molecules

Answer 9

Symmetrical
NO LONE PAIRS ON CENTRAL ATOM
2 atoms, subtract electronegativity with a difference of 0.0 - 0.4

Question 10

Polar Molecules

Answer 10

Asymmetrical
LONE PAIRS ON CENTRAL ATOM
2 atoms, subtract electronegativity with a difference of 0.5 - 1.6

Question 11

Hydrogen Bond Forces

Answer 11

Special kind of Dipole force
Strongest IMF
Extremely polar molecules
Huge difference in electronegativity
When H bonds with either N, O, or F it is hydrogen bonding

Question 12

Boiling Points

Answer 12

Temperature at which something boils (IMFs break)
Molecules with strong IMFs have higher boiling points
If they have the same IMF than molecules with higher molar mass

Question 13

Vapor Pressure

Answer 13

Vapor = Gas formed when liquid evaporates
Vapor pressure = Pressure exerted by vapor particles
Easy to evaporate (weakest IMF)
If they have the same IMF than molecules with lowest molar mass

Question 14

Enthalpy

Answer 14

The energy stored in bonds
(delta)H = Hproducts - Hreactants

Exothermic:
Change is negative
Reactants –> Products + Heat

Endothermic:
Change is positive
Reactants + Heat –> Products

Question 15

1st Law of Thermodynamics

Answer 15

Universe favors a DECREASE (exothermic) in enthalpy

Question 16

Entropy

Answer 16

Chaos, randomness

High <—————————————> Low
Disorder Order
Gasses Liquids Solids
High temp Low temp
Mixtures (solutions) Pure substances

Question 17

2nd Law of Thermodynamics

Answer 17

The universe favors an INCREASE in entropy (chaos)

Question 18

Activation Energy

Answer 18

Energy needed to run the reaction

Question 19

Catalyst

Answer 19

Speeds up reaction
Lowers the activation energy

            Catalyst Reactants -------> Products