AP Chemistry Unit 3 Review

intramolecular forces

bonding forces that occur within a molecule or compound

bonds in molecules

covalent bonds

bonds in ionic compounds

ionic forces

bonds in metals

metallic bonds

water molecule bonds

2 hydrogen atoms are covalently bonded to an oxygen atom in one single unit

attraction between water molecules

attract each other to form larger volumes through IMFS

intermolecular forces

attractive forces between molecules

cohesive forces

attractive forces between the same chemical species

example of cohesive forces

water is attracted to itself, allowing water to form droplets

adhesive forces

attractive forces between different chemical species

example of adhesive forces

water is attracted to cellulose which helps trees absorb water

electrostatic forces of attraction

all IMFS are caused by electrostatic forces of attraction

Coulumb’s law strikes again!

causes of intermolecular and intramolecular bonding

coulombic attraction between the charged particles

strength of intramolecular and intermolecular forces

intermolecular forces are much weaker than intramolecular forces, because the charges are smaller and the distances are greater between molecules

3 states of matter

solid, liquid, or gas 

properties of matter in solid form

• particles are close together and held in fixed position (low entropy) for attractive forces 

• vibrate in place and individual atoms have limited movement 

properties of matter in liquid form

• Particles easily slide past each other

• Attractive forces frequently break and reform

• The volume is constant

• The shape depends on the container

properties of matter in gas form

• particles are in constant, independent motion

• attractive forces are very low - no fixed position or volume 

• gasses are extremely compressible 

compressibility

measure of how much a substance’s volume can be decreased when pressure is applied 

2 formations of solids

amorphous: solid that doesn’t have orderly arrangement of particle

crystalline: solid containing orderly repetitive pattern of particles

4 types of solids

ionic, molecular solids, network covalent solids, metallic solids

bonds in ionic compounds

ionic bonding forces

bonds in molecular solids

intermolecular forces

bonds in network covalent solids

covalent bonding forces 

SOMETIMES IMFS but not too common

bonds in metallic solids

metallic bonding forces

ionic compounds composition

crystalline solids of cations and anions

examples of ionic compounds

NaCl, Mg(OH)2

properties of ionic compounds

strong, brittle, dissolve into cations and anions, low vapor pressures, high melting and boiling point 

comparing attraction in ionic compounds and covalent bonds

electrostatic attraction in ionic compounds stornger than IMF forces in covalent bonds

factors determining strength of ionic compounds

distance between ions and charge of the ions (coulumb’s law)

molecular solids composition

intermolecular forces (weaker than ionic solids) 

examples of molecular solids

ice, dry ice, iodine, sulfur

properties of molecular solids

amorphous/crystalline, low melting + boiling, poor conductors 

network covalent solids composition

solid structure composed of a large amount of nonmetals and/or metalloids held together through covalent bonds 

examples of network covalent solids

diamond, graphite, silicon dioxide, silicon carbide

properties of network covalent solids

amorphous/crystalline, strong material, high melting + boiling, poor conductor

allotropy

different forms at which chemical elements can be arranged

examples of allotropes

diamond and graphite are allotropes of carbon

2D network solids

atoms are connected through covalent bonds in 2D network

IMFS hold 2D networks 

3D Network Solid

atoms that are connected through covalnet bonds in a 3D network 

(locked in place and very STRONG) 

metallic solid composition

solid made of metallic protons immersed in a sea of delocalized electrons

examples of metallic solid

lithium and iron

metallic solid properties

crystalline solid, malleable, ductile, good conductors

general chemical formula of molecular solid

nonmetals

general chemical formula of network solids

metalloids

general chemical formula of ionic compounds

metal and nonmetal and/or polyatomic ion

general chemical formula of metals

metals

causes of a phase change

energy is added or removed - attractive forces to break apart or come together

stronger the attractive force

the more energy required to break the force

strength of the force depends on

the types of chemical bonds and the composition and positions of the interacting particles.

london dispersion forces

attractive forces between all substances that result from the motion of electrons

electrons are in constant movement

not always evenly dispersed around a chemical species.  

Temporary dipole

A temporary attractive force caused by the temporary positions of electrons

Polarizability

• The tendency for a molecule to produce more dipole interactions

Polarizability increases with the size of the electron clouds of the molecules

strength of the london dispersion forces in a substance depends on the polarizability of the electrons

concept for polarizability

The larger the electron clouds, the further the electrons are from the nucleus, and the easier the electrons can polarize

increase in mass, surface area, or pi bonds

more chances for electron clouds to form dipoles and strength increases

LDFs in heavier molecules (mass)

LDFs are strongest IMFS due to the large volume of electron clouds

LDFS with surface area

butane has a higher surface area which causes it to have a higher melting and boiling point 

LDFs with pi bonds

compounds with higher pi bonds will have higher melting + boiling points due to the pi bonds having more electron orbital overlap and electrons closer together to each other 

effect of pi bonds

increase electron density and electron interactions 

dipole interactions

attractions between chemical species where at least one of the species is a polar molecule 

general types of dipole interactions

dipole-induced interactions 

dipole-dipole

ion-dipole

dipole induced interactions

temporary dipole induced from a polar molecule interacting with the electrons in a nonpolar molecule

dipole-dipole

intermolecular forces between polar molecules that form from coulombic attractions between partially positive and partially negative parts of molecules

ion dipole 

attraction between a dipole from a molecule and the charge of an ion

at similar molar masses, molecules with dipole-dipole forces are stronger than molecules with only LDFs

molecules with dipole-dipole also contain LDFs, increasing the total strength 

polar molecules dissolve

polar molecules

example of polar molecules dissolving polar molecules

• Water will dissolve sugar more easily than it will dissolve flour.  Sugar has a higher polarity than flour

the strength of dipole-dipole interactions increases with

magnitude and positions of the dipoles

example of dipole-induced dipole

• Oxygen is nonpolar, but is able to dissolve in water

  • The movement of electrons in an oxygen molecule can cause a temporary attraction to the partial positive and negative charges to each other

strength of dipole-induced dipole

strength increases with the polarity of the molecule and the polarizability of the nonpolar molecule 

hydrogen bonds

extremely strong type of dipole-dipole force that exists between polar molecules with a hydrogen atom attached to an oxygen, nitrogen, or fluorine atom

cause of strength of hydrogen bonds

hydrogen only has one electron and as the electron spends more time near an electronegative atom, the proton becomes more exposed and is more attracted to electronegative atoms

hydrogen bonds and chemical bonds

even though it is a strong intermolecular force, it is much weaker than chemical bonds

explanation for why water is liquid at room temperature

hydrogen bonding

properties of water attributed to polarity and strong hydrogen bonds

universal solvent, highly polar, expands when frozen, found as liquid/solid/gas

gravitational forces compared to ion-dipole forces

ion-dipole forces are stronger than gravitational forces

strength of IMFS at similar masses

ion-dipole, hydrogen bonds, dipole-dipole, london dispersion

if molecules have the same types of IMFS

strengths increase with mass and complexity.

properties that increase with strengthening attractive forces

melting/boiling point

heat of vaporization and heat of fusion

surface tension

viscosity

capillary action

vapor pressure

volatility

solubility

melting and boiling point

temperature at which a substance changes phases

heat of vaporization and heat of fusion

amount of energy rquired for a substance to change phases

causes of phase changes

when attractive forces break

surface tension

amount of energy required to increase the surface area

liquid molecules minimize surface area

stronger attractive forces are more likely to pull liquid into a sphere

viscosity

tendency for a liquid to resist flow

viscosity explanation

when attractive forces are stronger, particles are strongly attracted to each other and don’t flow around each other easily

capillary action

rise of a liquid due to the interaction between cohesive and adhesive forces

explanations for capillary action

capillary action increases with increasing adhesive attractions

vapor pressure

pressure applied from the collisions of vaporized particles in equilibrium within its liquid phase

explanations for vapor pressures

in a closed container, molecules with weaker IMFS will not evaporate as frequently and there will be less overall collisions 

volatility

how easily a substance evaporates

takes less time to evaporate when the molecules are less attracted to each other 

solubility

maximum amount a substance will dissolve in a solvent 

relation of solubility with cohesion and adhesion

solubility decreases with increasing cohesive strength and decreases with adhesive strength

kinetic molecular theory of gasses

• gasses are made of particles with no volume

• no attractive or repulsive forces

• particles are in constant random motion 

• collisions are elastic 

• kinetic energy is directly proportional to the temperature

gasses are compressible

volume of gas depends on size of the container

gas described by 4 properties

volume (amount of space a container takes up)

molar amount (amount of particles in the sample)

temperature (average kinetic energy of the particles)

pressure (force of particles exerted over an area) 

gas laws

group of laws in the form of equations that state the relationships between gas properties in an ideal gas

kinetic molecular theory defines volume of an individual gas particle as 0

this is because particles in the gas phase are so far apart from each other

as more particles are added to a group of particles

the volume will expand