AP Chemistry Unit 3 Review Summary: Properties of Substances and Mixtures

Properties of Substances and Mixtures

➢​Intermolecular forces (3.1)
○​ Coulomb's Law
■​ Governs bonding strength; all bonding based on attraction
that exist between charged particles
○​
○​ LDFs
■​ Temporary Dipoles → Induced dipoles
■​ Usually the weakest attraction
■​ Present in all substances
■​ The larger the partial charges the stronger the LDF
■​ The larger the #of electrons → increased polarizability
​ **Bigger atoms → stronger LDFs
○​ Dipole-Dipole (D-D) bonds
■​ Permanent dipoles
**Not all molecules that have polar bonds are polar
themselves
■​ Occurs between POLAR molecules
○​ Hydrogen (H) bonds
■​ H atoms bonded to N,O, or F
■​ Strongest INTERmolecular bond (and Thus tend to have
higher Melting and Boiling points)
➢​Properties of solids (3.2)
○​ Substances with strongest IMFs, most likely to be found in solid
phase at STP


Ionic compounds Metals Covalent Networks Covalent
molecules

What to ●​ Solid @ STP ●​ “Sea of ●​ Most have ●​
know ●​ Brittle electrons”; tetrahedral

, Properties of Substances and Mixtures
●​ High melting delocalized structures
and boiling electrons ●​ Most also have
points ●​ Malleable, sp³ orbital
●​ Conductive ductile ●​ Graphite is the
when ●​ conductive exception
dissolved ●​ Very high MP
& BP

Examples NaCl Alloys Diamond
KCl -​ Interstitial Graphite**
-​ substitutional WC
Si
SiO2


○​
➢​Solids, liquids and gasses (3.3)
○​ Solids can have a crystalline(structured) or amorphous (irregular
arrangement)
■​ Have limited movement; vibrate
○​ Liquids are continually moving and colliding
○​ Gasses’ particles are in constant motion
■​ Easier to compress due to space between particles
○​ Viscosity- resistance to flow
➢​The Ideal Gas Law (3.4)
○​ PV = nRT