Gas Laws. Part 1: Kinetic Theory (most of this should be review)
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Transcript of Gas Laws. Part 1: Kinetic Theory (most of this should be review)
Gas Laws
Part 1: Kinetic Theory(most of this should be review)
Kinetic Theory of MatterAll matter is moving.Kinetic Energy is the energy of
motion.Temperature is a measure of Kinetic
Energy.Higher temperature indicates more
motion.Motion stops at 0 K (-273˚C)
Kinetics of PhasesSolids the particles have strong Inter-
molecular forces (IMF) with each other but vibrate in place.
Liquids have some IMF but can change position relative to each other.
Gases have very low IMF and have very little interaction with one another.
So...
Solids have a definite shape and volume.
Liquids have definite volume but not definite shape (take the shape of their container)
Gases have no definite shape or volume (expand to fill size and shape of container).
TemperatureMeasure of the average kinetic energy.
Some particles can be moving very fast.
Some will move very slowly.Most are average.
Vapor Liquid Equilibrium
Stoppered flask, particles cannot escape.
Open beaker they can – eventually will evaporate.
Part II: Properties of Gases
Air Pressure is Due to Gravity
Remember STP?
Standard Air Pressure is measured at Sea Level: 101.3KPa
CompressibilityGas molecules are very smallThe spaces between them are very
largeThe molecules can be forced closer
togetherThey can absorb a lot of energyE.g. car air bags
Intermolecular ForcesThe molecules are randomly moving
very fastThey move in straight-line pathsOnly change direction when they
bump into somethingThe molecules are SO far apart that
the IMF are considered to be zero
Variables in the Gas Formulas
P = pressure in kilopascals (kPa)V = volume of the gas in litres (L)T = temperature in kelvins (K)n = number of moles
Δ Moles, Δ PressureVolume remains constantTemperature remains constantDoubling the number of gas
particles (moles) doubles the pressure
Δ Volume, Δ PressureTemperature remains constantNumber of particles (moles) remains
constantDecreasing the volume by half will
double the pressure
Δ Temperature, Δ PressureVolume remains constant.Number of moles remains constantDoubling the temperature will
double the pressure
Part III: Gas Laws
Boyle’s Law
Temperature remains constantPressure goes up, volume goes
downPressure goes down volume goes up
Inverse relationship creates a curve, not a line…
Charles’s Law
Pressure is constant
Temperature goes up, volume goes up
Temperature goes down, volume goes down.
The Mylar Balloon on a cold day…
Demo
Gay-Lussac’s Law
Volume is constantTemperature increases, pressure
increasesTemperature decreases, pressure
decreases.
Ideal Gas LawPV=nRT where R is the gas law
constant 8.31 L•kPa
Ideal GasesFollow the law preciselyThe particles must have no volumeMust have no IMFNo ideal gases exist
Guess where we find this…
The most ideal gases are H2 and He