Gas Laws! Introduction to Gas Laws.

Key Terms  Pressure: the amount of force per unit area of surface  Newton: the SI unit for force  Pascal: the SI unit of pressure

Properties of Gases  Gases have unique properties because the distance between particles is much greater than solids or liquids!  Gases expand to fill any container.  Gases are fluids, as they are able to flow  Gases have lower densities than solids or liquids.  Most of the volume occupied by a gas is empty space, as the molecules are further apart.

Properties Continued.  Although gases have lower densities compared to solids and liquids, they can be more or less dense than one another.  Gases are highly compressible.  No volume equates to a lot of empty space!  Compressing gas particles moves them closer together.

Air Pressure  Collisions with gas molecules and with the surface of the earth cause air pressure.  Less dense gases are at higher altitudes. Less dense air exerts less pressure, as their molecules collide less often.  Your ears pop when you are in an airplane, as the air inside your ears changes to match the same pressure as the outside air.

Kinetic Molecular Theory  Model used to predict gas behavior.  States:  Gas particles are in constant, random motion  Gas particles a far apart relative to their size *fluidity, compressibility*  Pressure exerted by a gas is a result of collisions of the molecules against the walls of their container.

Pressure nWhich shoes create the most pressure?

Measuring Pressure Barometer  measures atmospheric pressure. The column falls until the pressure exerted by its weight equals the atmospheric pressure. nMercury Barometer

Pressure Units  KEY UNITS AT SEA LEVEL kPa (kilopascal) 1 atm 760 mm Hg 760 torr 14.7 psi

Converting Pressure Units - Practice  Carbon dioxide has a pressure of 72.7 atm. What is this value in pascals?  The vapor pressure of water at 50ºC is 12.33kPa. What is this value in mm Hg?  Convert 100 kPa to atmospheres.  A tire is inflated to a 44.7 psi. Calculate the total pressure in pascals.

Standard Temperature and Pressure  At sea level, the atmosphere keeps mercury in a barometer at 760 mmHg or 1 atmosphere.  Standard Temperature & Pressure :  0ºC and 1 atmosphere (atm)