Chemistry Chapter 13

what effect does increasing the temperature of a liquid have on its vapor pressure

increases vapor pressure

why do molecular solids have a lower melting point than ionic solids

not as great of attraction between particles

what does the abbreviation STP stand for and what are the conditions of STP

standard pressure and temperature conditions - 0 degrees celsius (273K) and 1 atm

which has greater kinetic energy, an ice cube at 0°C or water at 0°C

both have the same kinetic energy (same temperature = same KE)

do liquids have a higher, lower, or equal amount of KE than gases

depends on temperature. at the same temperature - all are the same

what is the boiling point of water? what is the normal boiling point of water?

depends; when vapor pressure = external pressure; when external pressure = 1 atm (100°C)

why do different liquids have different normal boiling points

different intermolecular activities

what is the relationship between Kelvin temp of a substance and the kinetic energy of its particles

direct relationship

melting point

temperature at which a solid becomes a liquid

three main ideas of kinetic theory

1. gases are small, insignificant volume and independent 2. gases move in rapid, random motion 3. collisions are perfectly elastic

allotropes

2 different forms of the same element

how does the average KE of the gas molecules inside a canister change when the canister is heated from 27°C (300K) to 627°C (900K)

3 times faster

Which are true for a gas: a - fill their container b - are compressible c - their pressure is not affected by temperature d - have mass e - are tightly packed f - move chaotically g - have high density

a - fill their container b - are compressible d - have mass f - move chaotically

if liquid A has a vapor pressure of 50.5kPa at 20°C and liquid B has a vapor pressure of 63.5kPa at 20°C, a) which liquid has greater intermolecular forces b) which liquid would boil first if the temperature is raised c) which liquid would evaporate easier

a) A because it is not evaporating easily b) liquid B c) liquid B - higher vapor pressure = easier to evaporate

what one word describes what causes gas pressure? would the pressure increase or decrease as you go up a mountain?

a) collisions b) decrease (less air molecules to collide)

why are pressure cookers recommended for cooking at high altitudes

at high altitudes, water can't get to 100°C so need to increase pressure

what are the three units of pressure

atmospheres (atm), pascals (kPa), and millimeters of mercury (mmHg or torr)

what is the difference between the boiling point and the normal boiling point of a liquid

boiling point - depends on external pressure normal boiling point - always at STP (1 atm)

how is evaporation in a closed container different than evaporation in an open container

closed container - will reach equilibrium

as you go up a mountain, does the atmospheric pressure increase or decrease

decrease (less gas = less pressure)

if the intermolecular forces increase in a series of liquids, would you expect the vapor pressure to increase or decrease

decrease (stronger intermolecular forces = lower vapor pressure)

is it easier or harder to boil water on top of a mountain? will the temperature of the water be different?

easier to boil, since water boils at lower temperature than at sea level but harder to cook food

what is it called when a molecule escapes from the surface of a liquid and becomes a gas?

evaporation (surface = evaporation)

main difference between gas pressure and atmospheric pressure

gas pressure - in a container (tire) atmospheric - due to open air

atmospheric pressure

gas pressure due to atmospheric (air) gases

condensation

gas → liquid

deposition

gas → solid

why are gases much different in density than liquids? which one can easily be compressed?

gases have a lot of space between molecules, gases are far apart and liquids are closer together gases - easily compressed

which will have a higher vapor pressure at any given temperature, water or gasoline?

gasoline

explain why boiling (or evaporating) is a cooling process

highest energy particles leaving = lower average left; takes energy to break forces of attraction

kinetic theory

idea of particles in constant MOTION

what happens to a liquid when its vapor pressure equals the external pressure

it boils

vaporization

liquid → gas

freezing

liquid → solid

what is one physical property that would help you distinguish a molecular solid from an ionic solid

melting point ionic - high melting point

describe what happens when a solid is heated to its melting point

molecules moving fast enough to break attractive forces and move around

what is meant by an elastic collision

no energy is lost - bounce off without losing energy

SI unit of pressure

pascal (kPa)

what are 3 different units we will use to measure pressure

pascal, mmHg, atmosphere

triple point

point at which sold, liquid, and gas exist together

what happens to pressure when temperature is decreased?

pressure decreases

what happens to pressure when volume is increased?

pressure decreases

vapor pressure

pressure exerted by a liquid turning into gas

what happens to pressure when the amount of gas is increased?

pressure increases

why might you have trouble breathing on top of Mount Everest

pressure so low - already doesn't move in or out of lungs as volume changes

how would the pressure change, if at all, if the number of gas molecules inside a can was decreased, such as when a shaving cream can goes empty

pressure would decrease due to less collisions

explain what is happening at the molecular level when a dynamic equilibrium occurs

rate of evaporation = rate of condensation (still lots of action)

what happens to the temperature during a state change

remains constant

why does a liquid stay at a constant temperature when it is boiling? where is all the added heat going?

requires energy for a liquid to change state, added energy used to break attractive forces (potential energy)

gas pressure

result of collisions of gas with an object

what is some everyday evidence that suggest matter is in motion

smell them from far away

amorphous solid

solid with no definite shape or pattern

sublimation

solid → gas

melting

solid → liquid

what is significant about the temperature absolute zero

the kinetic energy = zero; all motion has stopped

what is wrong with the statement "the airplane door came open and he got sucked out of the plane"

the person could get PUSHED out, but not sucked out. nature only blows

put these 3 substances in order from lowest vapor pressure to highest vapor pressure: water, vegetable oil, and gasoline

vegetable oil, water, gasoline

if you were to remove a lid from an ice cream container in your freezer that has been there for a while and notice ice crystals on the lid, explain what happened

water frozen (in ice cream) SUBLIMES and hits lid, then are DEPOSITED

why and how does sweating keep you cool on a hot day

water on your skin absorbs heat to evaporate and takes heat with it

boiling point

when external pressure equals vapor pressure

how do you measure average KE

with a thermometer