Temperature rises because KE increases

fusion occurs between a solid and liquid

this phase is endothermic (FUSION)

vaporization occurs between a liquid and gas

when energy is added to a substance in a single phase as heat the temperature rises

but when energy is added to a susbtance in 2 phases the temperature does not change

This is because the added energy is used to overcome intermolecular forces rather than increasing kinetic energy, resulting in a phase change.

phase transitions from liquid to solid and from gas to liquid have negative heat

phase transitions from solid to liquid and from liquid to gas always have a positive heat

chemical bonding is based on electrostatic interactions

INTRAMOLECULAR FORCES: atoms are held together within molecules

INTERMOLECULAR FORCES: all molecules feel attractive forces towards other molecules, forces that hold the molecules to one another (between molecules)

These forces play a crucial role in determining the physical properties of substances, such as boiling and melting points, as well as their solubility in different solvents.

whether something will be a solid, liquid, or gas at room temperature is determined by the strength of the intermolecular forces

the pressure of the liquid vapor (the gas molecules that are present) at equilibrium is called the VAPOR PRESSURE

higher vapor pressure= weaker IMF’s

lower vapor pressure= stronger IMF’s

Vapor pressure can also be influenced by temperature, as increasing the temperature generally increases the kinetic energy of the molecules, leading to higher vapor pressure.

boiling occurs when: vapor pressure= external pressure

a higher boiling point means that more energy needs to be put into the system to overcome the IMF between the molecules

stronger IMF= higher boiling point

Pvap(solid)= Pvap(liquid)

stronger IMF leads to lower vapor pressure

-stronger IMFA leads to higher boiling and higher melting point

higher temperature & lower pressure: gas phase

low temperature: solid phase

1 atm or 76 cm of Hg( mercury) called the normal freezing point

if you continue to heat gas the temperature increases

the point where solid, liquid, and gas meet is called the triple point

SUBLIMATION: is the process associated w/ the conversion of a solid to gas

3 kinds of species we must consider:

ionic species: cations & anions, has the strongest electrostatic attraction

polar molecular species: dipole, has no net charge, weaker then ionic but stronger than 2 nonpolar molecules

non polar: symmetric distribution of charges, molecular species, and no dipole

interactions among molecules are called intermolecular forces. These forces are weaker then ionic interactions.

we do not consider ionic interactions to be IMF’s

there are 3 types of IMF’s we must know:

1. dipole- dipole interactions

2. hydrogen bonding: strongest IMF

3. london dispersion force: weakest IMF

there are only 3 electronegative atoms that can form hydrogen bonds: nitrogen, oxygen, & fluorine

not every polar molecule can form hydrogen bonds, but every molecule that forms hydrogen bonds will be polar

what kinds of compounds can make H bonds: any molecule that has an H atom directly attached to a N,O, or zF atom will experience hydrogen bonds as the IMF that hold the molecules together

London dispersion forces occur between almost all atoms/ molecules (due to induced dipoles) and are proportional to size and shape: larger atoms have a larger electronic cloud, thus they have an increased polariziability

molecules w/ larger IMF’s have higher boiling points and melting points

molecules w/ smaller IMF’s have higher vapor pressure (these species are more volatile)

The phase transition from liquid to gas is boiling. If a gas was to be converted into a liquid, that would be called condensation.

The phase transition from solid to gas is sublimation. If a gas was to be converted into a solid, that would be called deposition.

The phase transition from solid to liquid is melting. The reverse phase transition, from liquid to solid, is freezing.

The phase change from liquid to gas is called vaporization.

The predominant intermolecular force in Br2Br2 is dispersion because the molecule is nonpolar, so you would expect it to have the weakest intermolecular forces and the highest vapor pressure.

The predominant intermolecular force in H2OH2O is hydrogen bonding because it contains HH bonded to O,O, so you would expect it to have the strongest intermolecular forces and the lowest vapor pressure.

All of the given compounds are nonpolar, so the relative strengths of the dispersion forces, also known as van der Waals forces, will determine the relative boiling points.