GasesUnit 9

Properties of Gases

Independent particles, moving in straight lines

Change direction with collisions Travel randomly Assume shape of container and

volume of their container Large amount of empty space Compressible No attractive forces between particles

More Properties

Fluidity – gas particles glide and flow past each other

Expansion – fill any container Compressibility – can decrease the

volume Diffusion – spontaneous mixing of

two gases, flow until evenly distributed. Flow from an area of high concentration to an area of low concentration.

Pressure

Dependent on the force of the collision and the number of collisions that occur between particles.

Pressure = Force/Area

Atmospheric or barometric pressure – results from collisions of air molecules with objects on earth.

Devices to Measure Pressure

Manometer

Barometer Developed by Evangelista Torricelli

Pressure gauge

Pressure Units

SI unit = Pascal (Pa) A pascal is small so normally the

kilopascal (kPa) is used which is 1000 Pascal.

Atmosphere (atm) 1 atm is the atmospheric pressure at sea

level. Pounds per square inch (psi) Millimeters of mercury (mmHg) Torr

Boyle’s Law

Named after Robert Boyle It says that at a constant

temperature pressure and volume are inversely proportionate.

As volume goes up the pressure goes down and vice versa.

P1V1=P2V2

Graphing Boyle’s Law

Applying Boyle’s Law

Weather Balloon Helium vs. Air Equilibrium

Airplanes Pressure as you climb Volume

Kinetic explanation of Boyle’s Law

Bike Pump

Practice Problem

The maximum volume of air that a weather balloon can hold without rupturing is 22,000L. It is designed to reach an altitude of 30 km. At this altitude, the atmospheric pressure is o.o125 atm. What maximum volume of helium gas should be used to inflate the balloon before it is launched?

Practice Problem 2

Two liters of air at atmospheric pressure are compressed into the 0.45 L canister of a warning horn. If its temperature remains constant, what is the pressure of the compressed air in the horn?

Charles's Law

Named after Jacques Charles States that at a constant pressure the

volume of a gas is directly proportional to its kelvin temperature.

As temperature goes up volume goes up.

Temperature must be in Kelvin:K=oC +273

Graphing Charles’s Law

Applying Charles’s Law

Lid in refrigerator Air hot Cools down and sinks

Tires on the road Too inflated pops tire

Kinetic explanation of Charles’s Law

Balloon

Practice Problem

A balloon is filled with 3.0 L of helium at 22oC and 760 mmHg. It is then placed outdoors on a hot summer day when the temperature is 31 oC. If the pressure remains constant what will the volume of the balloon be?

GAY- LUSSAC’S LAW

Named after Joseph Gay-Lussac States that at a constant volume the

pressure and temperature of a gas are directly proportional.

As temperature goes up pressure goes up.

Temperature must be in Kelvin: K=oC +273

Graphing Gay-Lussac’s Law

Applying/Kinetic explanation of Gay-Lussac’s Law

Aerosol can in fire Pressurized can Increase temp= explosion

Combined Gas Law

All three gas laws put together.

Temperature must be in Kelvin: K=oC +273

STP = Standard Temperature and Pressure Defined as 273K and 1 atm

Practice Problem

A toy balloon has an internal pressure of 1.05 atm and a volume of 5.0L. If the temperature where the balloon is released is 2ooC, what will happen to the volume when the balloon rises to an altitude where the pressure is 0.65 atm and the temperature is -15 0C?

Health

Hyper: above or excessive Hyperbaric refers to pressure that is

greater than normal Hyperbaric chambers uses:

cure burns Decompression sickness Anemia Infections