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
