gases part 1

do gases ALWAYS fill their containers?

yes

how compressible are gases?

very compressible

how fast do gases diffuse?

rapidly

what happens to gases when they are heated?

they expand

do gases mix readily with other gases?

yes

why do confined gases have higher pressure when heated?

• more thermal energy = more kinetic energy

  • particles move faster

• more kinetic energy = higher pressure

  • gases expand

what does kinetic molecular theory (KMT) explain?

behaviour of gases, basis for gas laws

what are the most important traits to assess with gases?

• temperature

• pressure

• volume

• mass/mols of gas

what is majority of a gas’s volume? (KMT)

empty space, the amount taken up by the molecules are barely noticeable

what does compression do to a gas’s volume? (KMT)

reduces empty space between gas molecules

how do gas molecules move, and why? (KMT)

in a straight line

• gases do not experience intermolecular force strong enough to change their course

• does not get pulled towards anything

do gas molecules collide? (KMT)

yes, with each other and the walls of the container

why do gases diffuse? (KMT)

constantly moving

how is energy affected by temperature? (KMT)

• directly proportional

  • high temp = faster moving molecules, and vice versa

how do gas molecules interact w e/o and the walls when they collide? (KMT)

elastic collision

• collide with no loss of kinetic energy

• second law of thermodynamics

ideal gas

behaves perfectly in all conditions of pressure, temps, and volume

are assumptions for ideal gases true in reality?

no

assumptions about the volume of an ideal gas:

• low pressure & low volume

  • molecules are far apart, never collide

  • molecular size is insignificant, take up almost no space

reality about volume of a real gas:

• high pressure, high volume

  • gas molecules forced closer together, collide often

  • molecular size is actually significant, they take up some space

pressure of gas:

how often they collide with the wall of the container

• high pressure = frequent collisions

assumptions about the temperature of an ideal gas:

• high temperature

  • random, constant straight motion

  • no attractive forces exist

assuming the temperature of an ideal gas, do gases condense?

no, since they only condense at low temperatures

reality about temperature of a real gas:

• lower temperatures

  • attractive forces do exist between molecules

assuming the temperature of a real gas, do gases condense?

yes they do

• intermolecular forces make them stick together, gas becomes liquid

assuming the interactions of a ideal gas, do gases condense?

• elastic collisions

  • no energy is lost

reality about interactions of a real gas:

• lose a little energy when collision occurs

what is the pressure of a real gas compared to an ideal gas?

• pressure of real gas is slightly lower than pressure of ideal gas

kinetic energy

measure of the energy of motion

temperature

average kinetic energy of a particle in a substance

what is the relationship between motion and temperature?

more motion = high kinetic energy = higher temperature

what are the lower and upper limits of temperature?

• lower limit: absolute zero (-273.15C)

• upper limit: N/A

absolute zero

theoretical temp that has never been reached

kelvin scale

DIRECT measure of the average kinetic energy (temp) of a substance

how does a change in temperature compare for celsius and kelvin?

• 1C increase = 1K increase

temp → kelvin conversion:

K = C + 273.15

kelvin → temp conversion:

C = K - 273.15

what are the sig digs for kelvin → temp conversion?

least # of decimal places

pressure

force per a unit of area

atmospheric pressure

amount of force exerted by air on all objects per unit area

how is atmospheric pressure measured?

with a barometer

standard temperature and pressure (STP)

0C, 100kPa

standard ambient temperature and pressure (SATP)

25C, 100kPa

ratio of pressure values

1 atm = 760mmHg = 101.325 kPa

boyle’s law

studies relationship b/w volume and pressure (INVERSE)

• temperature remains constant

relationship between volume + pressure

high volume, low pressure, vice versa

charles’ law

relationship between temperature and volume (DIRECTION)

• pressure stays constant

relationship between temperature + volume

high volume, high temperature, and vice versa

what do you use for sig digs of final answer?

sig digs of kelvin should be what counts

gay-lussac’s law

• relationship between temperature and pressure

  • volume is constant

combined gas law

no constant, pressure, temp, AND volume change (combines boyle’s and charles’s)

avogadro’s law

• relatioship between volume and mols (DIRECT)

  • temperature and pressure are constant

molar volume

same number of mols in specifc volume for all gases at same temp and pressure

law of combining volumes

• mole ratio in balanced chemical reactions tell us the volume ratio

  • constant temperature + pressure

are moles and volume conserved in a reaction?

they are not

what is conserved in a chemical reaction?

mass and energy