what is dispersion force

present in all molecules and atoms and increase with increasing molar mass; always weak in small molecules

why does having a larger electron cloud result in a greater dispersion force

because the electrons are held less tightly by the nucleus and therefore polarize easier

why do boiling points increase with increase strength of intermolecular forces

because more thermal energy is required to separate the particles from the liquid state into the gas state

what is dipole-dipole force

it exists in all molecules that are polar

has electron rich and electron deficient regions

what has higher melting and boiling points

polar molecules

what is miscibility

the ability to mix without separating into two states

what is a permanent dipole

molecules, such as acetone, are attracted to one another via dipole-dipole interactions

what is a hydrogen bond

strong attraction between the H atom and F, O, or N

what is the strongest intermolecular force that occurs in pure substances

hydrogen bonds

what is a ion-dipole force

occurs when an ionic compound is mixed with a polar compound; very strong with aqueous solutions

Pick the compound with the highest boiling point in each pair. Explain your reasoning

A) CH3OH or CH3SH

B) CH3OCH3 or CH3CH3COH

C) CH4 or CH3CH3

A) CH3OH - hydrogen bonding

B) CH3CH2OH- hydrogen bonding

C) CH3Ch3- bigger mass

In each pair of compounds, pick the one with the higher vapor pressure at a given temp

a) CH or CH3Cl

b) CH3CH2CH2OH or CH3OH

c)CH3OH or H2O

a) CH- smaller mass

b) CH3OH- smaller mass

c) H2CO - lacks hydrogen bonding

Which compound would you expect to have a greater surface tension: acetone or water. Explain

Water because surface tension increases with increasing intermolecular forces

Water in a glass tube that contains grease or oil residue displays a flat meniscus whereas water in a clean glass tube displays a concave meniscus. Explain

water experiences adhesive forces with glass that are stronger than its cohesive forces, causing it to climb the surface of a glass tube. water does not experience strong intermolecular forces with oil, so if the tube is coated in oil, the water's cohesive forces will be greater and it will not be attracted to the surface of the tube

which evaporates more quickly: 55 ml of water in a beaker with a diameter of 4.5 cm of 55 ml of water in a dish with a diameter of 12 cm

the water in the 12 cm dish will evaporate more quickley because the bigger the surface area, the more molecules to obtain enough energy at the surface and break free

which evaporates more quickly: 55 ml of water in a beaker or 55 ml of acetone in a beaker

acetone because it is more volatile than water and acetone has the higher vapor pressure bc it is lighter

how much energy is released when 65.8 g of water freezes

22 kj

an 8.5 g ice cube is placed into 225 g of water. Calculate the temp change in the water upon the complete melting of the ice

2.7 C

How much ice (in grams) would have to melt to lower the temp of 352 ml of water from 25 C to 5 C (assume the density of water is 1 g/ml) (heat of fusion is 6.02 kJ/mol)

87.99 grams

how much heat (in kj) is evolved in converting 1 mol of steam at 145 C to ice at -50 C. The heat capacity of steam is 2.01 J/g *C, and that of ice is 2.09 J/g*C (heat of fusion for steam is 2230, heat of fusion for water is 334, heat of fusion for ice is 6.02)

51.2 kj

what has the smallest surface area

sphere

what is viscosity

the resistance of a liquid to flow

where is viscosity greater in

substances with strong intermolecular forces because if molecules are more strongly attached to each other, they do not flow around each other as freely

what is capillary action

the ability of a liquid to flow against gravity up a narrow tube; like taking a blood sample

what is cohesive forces

the attraction between molecules in a liquid; cause the liquid to stay together

what is adhesive forces

the attraction between those molecules and the surface of the tube; causes liquids to spread out over the surface of the tube

what is vaporization

the process by which thermal energy can overcome intermolecular forces and produce a state change from a liquid to a gas

why does evaporation take faster than condensation

most of the newly evaporated molecules escape into the surrounding atmosphere and never come back

what increases the rate of vaporization

increasing temp

increasing surface area

decreasing strength of intermolecular forces

is motor oil volatile or nonvolatile

nonvolatile

is vaporization endothermic or exothermic process

endothermic

why do weak intermolecular forces result in volatile substances

because the intermolecular forces are easily overcome by thermal energy

what happens if the pressure increases in a liquid-vapor system

some of the vapor condenses, bringing the pressure back down to the equilibrium pressure

what is sublimation

the transition from solid to gas

what is deposition

the transition from gas to solid

why does sublimation occur at a greater rate than deposition

because of the most newly sublimed molecules escape into the surrounding atmosphere and never come back

is melting ice endothermic or exothermic

endothermic because it absorbs heat from the liquid

is freezing endothermic or exothermic

exothermic because heat is released

what takes less time: heat of vaporization or heat of fusion

heat of fusion

what is the triple point in a phase diagram

represents the unique set of conditions at which three states are equally stable and in equilibrium

what is unique about water

the solid form is less dense than its liquid form, which is why ice floats

water expands when it freezes