SCH3U Gases and Atmospheric Chemistry The Kinetic Molecular Theory This theory is a way to describe the ___________ of particles. It states that particles in all forms of matter are in constant motion, (either “__________”, “_________”, or “_________ _________”). motion vibratingslidingflyingaround

Assumptions of the Kinetic Molecular Theory Here are 3 assumptions of the kinetic theory as it applies to gases: (1) Gases are composed of _______ particles that do not exert attractive or repulsive forces on one another. (2) These particles are in constant ___________ _______ motion and ______________ with other particles. (3) When particles collide, kinetic energy, (K.E.), is _____________. K.E. is the energy of ___________. These types of collisions are called “_____________ elastic.” If you could play pool using gas particles, they would never stop bouncing around the pool table! NOT perfectly elastic!! tiny straight line collide conserved motion perfectly

How Temperature Affects the Kinetic Energy of a Gas The _________ the temperature, the __________ the particles move, so the _________ K.E. the particles have! (________ Relationship: As temperature increases, average K.E. increases.) At 0 K, (______________ ______), kinetic energy is also ________. Doubling the Kelvin temperature would ___________ the K.E. (Twice as hot means ________ the ___________ temperature.) Temp. Kinetic Energy higherfaster Directmore absolute zerozero double twiceKelvin

Gas Pressure When a gas particle collides with an object, it exerts a small __________. The result of simultaneous collisions from billions of gas particles upon an object causes gas pressure. How to Measure Air Pressure A barometer is the instrument used to measure air pressure. There are 2 types of barometers: (1) ____________ Barometer: a gauge measures how much a column of air in a container is squeezed together by the air pressure in the room. The column of air is trapped in an “____________________-like” diaphragm. It can expand and contract. A needle gauge ____________ to an air pressure scale on the container as it expands or contracts. force Aneroid accordion points

Aneroid Barometer

How to Measure Air Pressure (Continued) (2) _____________ Barometer: measures the __________ of a column of mercury, (Hg), usually in units of _____ or ___________. Here’s how to make a mercury barometer: Step 1: Fill a 1 meter long “test tube” completely full of Hg. Step 2: Fill a bowl with Hg. Step 3: Without letting any Hg escape, put the tube of Hg upside-down in the bowl of Hg. The ___________ of the column of Hg in the inverted tube will cause the level of Hg in the tube to initially ________. Above the Hg there is a ___________, so not all of the Hg escapes. The air pressure in the room is pushing __________ on the Hg in the bowl which pushes ______ on the column of Hg in the tube. As the air pressure in the room increases and decreases, the height of the column of Hg in the tube goes _____ and ___________! Mercuryheight mminches weight fall vacuum down up down

Mercury Barometer

Gas Pressure Conversion Factors The S.I. (metric) unit for pressure is the pascal, (_____). The standard air pressure (at sea level) is about _______ kiloPascals. All of the following pressures are also equal to standard pressure: __ atmosphere (atm) =_____ mm Hg = ______ inches Hg = ____ lbs/in 2 (psi) Practice Problem: The pressure on top of Mt. Everest is 253 mm Hg. What is this pressure in units of kPa, and inches of Hg? Pa mm Hg x 760 mm Hg kPa = 33.7 kPa 253 mm Hg x 760 mm Hg in. Hg = 9.96 in. Hg

How Altitude Affects Air Pressure The higher up you go the ______ air molecules there are, so there are ______ collisions which will cause _____ pressure. (______________ Relationship: As altitude inc., pressure dec.) *Examples: This is the reason why your ears pop in ____________, ____________, or driving up and down large hills. (Going deep under the water will also cause your ears to pop because of increasing __________ pressure.) Altitude Air Pressure less fewer Inverse elevatorsplanes water

Gas Laws Here is the _____________ relationship between the # of gas particles in a container and the volume and pressure of the container: As the # of gas particles _____________, the volume of a flexible container will ____________ if the temperature and pressure of the container remain constant. # particles ___, V ___ *Example: Blowing ______ air into a balloon makes it larger. As the # of gas particles ____________, the pressure of a rigid container will ____________ if the temperature and volume of the container remain constant. # particles ___, P ___ *Examples: Pushing the button on an aerosol can releases the gas and ___________ the pressure in the container. Adding too much gas into a rigid container could make it ___________ from too much pressure! qualitative increase ↑↑ more increase ↑↑ decreases explode

# of Gas Particles vs. Pressure

Here is the qualitative relationship between the pressure, temperature, and volume of a constant # of gas particles in a container: (1) ___________ Law: At a constant temperature, as the volume of a container __________ the pressure of the container will ___________. V___, P ___ *Example: Compressing the gas in a flexible container will _________ its volume. Gas Laws Pressure Volume Boyle’s ↑↓ decreasesincrease decrease

(2) ____________ Law: At a constant pressure, as the temperature of a container __________ the volume of the container will ___________. T___, V ___ *Examples: Heating a balloon will cause it to ___________. Taking a balloon outside on a cold winter day will cause it to _____________. If you could keep a gas from condensing, you could cool it off to absolute zero and the volume of the gas would be _________! Gas Laws (continued) Volume Temperature (K) Charles’s increasesincrease ↑ inflate shrink zero ↑

(3) ____________ Law: At a constant volume, as the temperature of a container __________ the pressure of the container will ___________. T___, P ___ *Example: Heating a rigid container causes the gas inside to move __________ which causes _________ pressure. Be careful! Too much heat will make it explode! Gas Laws (continued) Pressure Temperature (K) Gay-Lussac’s increasesincrease ↑ fastermore ↑

Practice Problems: P T V 1)A gas has a volume of 8.0 liters. If the Kelvin temperature doubles while the pressure remains constant, what will be the new volume of the gas? 2) A gas has a pressure of 4.0 atmospheres. If the volume of the gas is cut in half while the temperature stays the same, what will be the new pressure of the gas? 3) A gas has a pressure of 700 mm Hg. If the Kelvin temperature of the gas is tripled while the volume stays the same, what will be the new pressure of the gas? 4) A gas in a rigid container has a pressure of 2.0 atm. If you were to double the number of gas particles in the container, what would the new pressure become? “Quantitative” Gas Law Problems T ↑ x 2, V ↑ x 2…(Charles’s Law) New Vol. = 8.0 x 2 = 16 L V ↓ ÷ 2, P ↑ x 2…(Boyle’s Law) New Pressure = 4.0 x 2 = 8.0 atm T ↑ x 3, P ↑ x 3…(G-L’s Law) New Pressure = 700 x 3 = 2100 mm Hg # gas particles ↑ x 2, P ↑ x 2 New Pressure = 2.0 x 2 = 4.0 atm

The Combined Gas Law This equation combines all of the previous three laws into one convenient form. Boyles Law: = constant Gay-Lussac’s Law: = constant Charles’s Law: = constant T = constant V T P 1 x V 1 TK1TK1 P 2 x V 2 TK2TK2 = (initial conditions) = (final conditions) Using the Combined Gas Law requires you to have the temperature in _____________ units. The pressure and volume units can be anything as long as the initial and final units are ______ __________. Kelvin the same P T P x V

Often the volume of a gas is needed at “standard conditions.” For scientists, this means “STP”. Standard temperature is ______K, and standard pressure will be the pressure conversion factor that matches the ____________ unit of pressure kPa = 1 atmosphere (atm) = 760 mm Hg = 760 torr = 14.7 lbs/in 2 (psi) Practice Problems: 1) 80.0 mL of helium is in a balloon at 25.0˚C. What will the new volume of the balloon be if the temp. is raised to 100.0˚C? (Since pressure is not mentioned, it can be assumed that it was constant. You can thrown it out of our equation.) Standard Temperature and Pressure: (STP) P 1 = ______ V 1 = ______ T K 1 = ______ P 2 = ______ V 2 = ______ T K 2 = ______ 80.0 mL 298 K373 K ??? Plug the #’s into the equation and solve for V 2. (80.0) (298) = (V 2 ) (373) V 2 = 100 mL 273 initial

Practice Problems: 2) A rigid steel container is filled with neon under a pressure of mm Hg and a temperature of 325 K. If the temperature is reduced to standard temperature, what will the new pressure be? (Volume is constant and is left out of the equation.) P 1 = ______ V 1 = ______ T K 1 = ______ P 2 = ______ V 2 = ______ T K 2 = ______ mm 325 K273 K ??? Plug the #’s into the equation and solve for P 2. (760.0) (325) = (P 2 ) (273) P 2 = 638 mm Hg 3) A balloon at a pressure of 4.50 atmospheres, K, and a volume of 35.0 liters is changed to STP conditions. What will the new volume of the balloon become? P 1 = ______ V 1 = ______ T K 1 = ______ P 2 = ______ V 2 = ______ T K 2 = ______ 4.50 atm K273 K 1 atm Plug the #’s into the equation and solve for V 2. (4.5)(35.0) (300) = (1)(V 2 ) (273) V 2 = 143 L 35.0 L???

Avogadro’s hypothesis states that ________ volumes of gases (under the same temp. and pressure conditions) contain _______ number of particles. If containers have the same ____, ____, and ___, then they will have the same ____ of particles regardless of the _________ of the gas particle. You might think that a small gas molecule would take up ______ space than a large gas molecule, but it ___________ at the same _________________ and ______________!! Avogadro’s Hypothesis equal T P V # size less doesn’t temperaturepressure

A mole is a term for a certain ______________ of objects. 1 mole = 6.02 x objects Since this value is so huge, it is used to measure very small objects like ___________ and _______________. Gas Conversions Factors At STP conditions, 1 mole of any gas occupies 22.4 Liters of space. Here are the conversion factors: 1 mole = __________ particles = _____L (at STP) The Mole Concept number atomsmolecules 6.02 x

“Ideal” Gases Real gases, (like nitrogen), will eventually ___________ into a liquid when the temperature gets too ____ or the pressure gets too _____. If you want a gas to act more ideally, keep the temperature _____ and the pressure ______. That way, they will act more like an ideal gas and never have a chance of _______________. The best real gas that acts like an ideal gas is __________. It doesn’t condense until the temperature gets to ______K. Real Gas condense low high low condensing helium 4

The Ideal Gas Law An equation used to calculate the __________ of gas in a container (in units of _________.) The units for T = __________, V = _________, n = # of moles R = Ideal Gas Constant The value of R changes depending on the unit of ____________ used in the equation: R = 62.4 (mm Hg)(L)/(mole)(K) R = (kPa)(L)/(mole)(K) R = (atm.)(L)/(mole)(K) R = 2.45 (in. Hg)(L)/(mole)(K) amount moles KelvinLiters pressure

The Ideal Gas Law Practice Problems: 1)6.5 moles of a gas has a pressure of 1.30 atmospheres and it has a temperature of 20.0˚Celsius. What is the volume of the gas? 2) How many moles of gas are there in a 7.3 liter balloon with a pressure of 847 mm Hg and temperature of 395 K? ( ) ( ) = ( ) ( ) ( )1.30V K V = 120 L ( ) ( ) = ( ) ( ) ( )8477.3n K n = 0.25 moles

Dalton’s Law of Partial Pressure The ______ of each individual gas pressure equals the _______ gas pressure of the container. P (total) = P 1 +P 2 +P 3 … Practice Problem: A container has oxygen, nitrogen, and helium in it. The total pressure of the container is 2.4 atmospheres. If all of the partial pressures are the equal to one another, what are the partial pressures of the gases? sumtotal P gas = 2.4 atm ÷ 3 = 0.8 atm

How Temperature Affects the Vapour Pressure Vapour Pressure is simply the push of a gas above its liquid. As the temperature of a liquid increases, so does the ____________ of vapour particles. More vapour particles cause more ____________, therefore _______ vapour pressure. [___________ Relationship: (T ↑ Vapour Pressure ↑)] Low TemperatureHigh Temperature number collisionsmore Direct