Kinetic Molecular Theory 1) Gas particles do not attract or repel. 2) Gas particles are smaller than space between them.(almost all the volume of a gas is empty space) 3) Gas particles (atoms or molecules) are in constant random motion. 4) No Kinetic Energy is lost when gas particles collide. 5) All gasses have the same average K.E. at a given temperature.

GAS LAWS Basis of Gas Laws is the Interdependence of Gas Variables:  Volume  Pressure  Temperature  Number of Moles

STP (standard temperature and pressure) Standard temperature is either: 0° Celsius or 273 Kelvin (no ° sign) For these formulas, Temperature MUST BE IN KELVIN (remember 0 deg. K is the absence of all heat energy!) Standard pressure in several units: 1 atm = 101.3 KPa =760 mm of Hg = 760 torr The volume for one mole of a gas at STP is 22.4 L

(inverse relationship graph) Boyles Law When the temperature and the # of moles of a sample of a gas is held constant, its volume is inversely proportional to its pressure. In other words, as volume increases, pressure decreases, or as volume decreases, pressure increases. P1V1=P2V2 (inverse relationship graph) P V

Practice Problems If a gas has a volume of 100 mL when the pressure is 1.50 atm, what is the volume in mL when the pressure is increased to 4.5atm, and the temperature is held constant? Think first: If my pressure increases, what should the volume do?____________________ V1= P1= V2 = P2=

Practice Problems If a gas has a volume of 100 mL when the pressure is 1.50 atm, what is the volume in mL when the pressure is increased to 4.5atm, and the temperature is held constant? Think first: If my pressure increases, what should the volume do? (Decrease) V1= 100 mL; P1=1.5 atm; V2 =? P2= 4.5 atm 1.5 atm x 100 mL = 4.5 atm x ? mL 1.5 atm x 100 mL = ? mL = 33mL(decrease) 4.5 atm

Charles’ Law If pressure is held constant, when temperature increases, volume will increase. When the temperature decreases, volume will decrease. (directly proportional) To convert degrees Celsius to Kelvin add 273… because 0 K is the same as -273 °C

Charles’ Law V1 = V2 at constant pressure T1 T2 Remember, standard temperature is 273 K V1 = V2 at constant pressure T1 T2 Direct relationship graph V T

Charles’ Law So if you are solving for a variable V1T2 = V2T1 or V1 T2 = V2 T1

Gay-Lussac’s Law If volume is held constant, when temperature increases, pressure will increase. When the temperature decreases, pressure will decrease. (directly proportional) Temperatures must be in Kelvin.

Direct proportional graph Gay-Lussac’s Law Remember, standard pressure is 1 atm or 101.3 kPa P1 = P2 at constant volume T1 T2 Direct proportional graph P T

Boyle’s Law Robert Boyle (1627-1691). Son of Earl of Cork, Ireland

Boyle’s Law

Jacques Charles (1746-1823). Isolated boron and studied gases Jacques Charles (1746-1823). Isolated boron and studied gases. Balloonist.

Joseph Louis Gay-Lussac (1778-1850)

Which heel exerts more pressure on a surface http://genchem.chem.wisc.edu/demonstrations/Gen_Chem_Pages/05gasespage/collapsing_aluminum_can.htm http://www.delta.edu/slime/cancrush.html

http://www.kentchemistry.com/links/GasLaws/manBar.htm

P1V1T2=P2V2T1 Combined Gas Law We can use one big equation for all the laws except Dalton’s. This is called the Combined Gas Law. That means there are only 2 equations to remember P1V1 = P2V2 or rewritten… T1 T2 P1V1T2=P2V2T1

WEB SITE PhET Simulations.lnk http://phet.colorado.edu/simulations/sims.php?sim=Gas_Properties

Tricks Ignore the constants(they cancel out) Use P1V1T2=P2V2T1 Ignore the constants(they cancel out) Box the numbers AND units given!!! List out P1= V1= T1= P2= V2= T2= Temperatures in KELVIN!!! Remember, STP is 273 K and 1.0 atm (101.3 kPa, 760 torr, 760 mmHg) Plug and chug…

Example Problem #2 Calculate the moles that are in 19.7 L of gas at STP. 19.7 L X 1 mole = ? Moles 22.4 L 19.7 L X 1 mole = 0.881 moles

Ideal Gas Law The physical behavior of a single gas sample in terms of the pressure, volume, temperature, number of moles of gas present or PV =nRT P= Pressure V= Volume n= moles of gas R= ideal gas constant T= Temperature

Ideal Gas Law Assumes that Particles: take up no space have no intermolecular attractive forces follows the gas laws under all conditions of T and P

Ideal Gas Constant (R) An experimentally determined constant whose value in the ideal gas equation depends on the units used for pressure 0.0821 if in Latm/molK 8.314 if in LkPa/molK 62.4 if in LmmHg/molK

To Be Ideal Gases Must completely follow the gas laws Cannot liquify Must be at: low pressures high temperatures

Real vs Ideal Gases Most gases will behave like ideal gases except when: At extremely high pressures At low temperatures A polar gas A large gas molecule (C4H10)

Example Problem V = 3.0 L T = 3.00 x 102 K = 300K P = 1.50 atm Calculate the number of moles of gas contained in a 3.0 L vessel at 3.00 x 102 K with a pressure of 1.50 atm PV = nRT V = 3.0 L T = 3.00 x 102 K = 300K P = 1.50 atm R = .0821 Latm/molK n = ?

Answer: V = 3.0 L T = 3.00 x 102 K = 300K P = 1.50 atm R = .0821 Latm/molK n = ? PV = nRT P V n R T (1.5atm)(3.0L) =n(.0821 Latm/molK)(300 K) n = (1.5 atm)(3.0 L) . (.0821 Latm/molK)(300 K) n = .18 mol