Gas Laws Chemistry Semester II Notes

Characteristics of Gases A. Properties of Gases  Any amount of gas will expand and contract to occupy the entire volume of its container.  All gases with equal volumes will have equal numbers of particles  Gases typically have low densities.  Gases are highly expandable and physically behave alike in response to pressure and temperature changes.

Gases continued  Temperature changes effect gases more than liquids.  Particles in gaseous phase are always moving in a constant random motion. They are not in any fixed position.  Size of the gas particles is extremely small when compared to the space between them.

B. Pressure and Gases  Gas pressure results from molecules colliding with their container.  Measure of pressure is in force/area.  Pressure in a closed system is equal in all directions. –Average air pressure at sea level is kPa (kilopascals) –1 pascal = 1 N/m 2 (where N = Newton; a force) –1 kPa = 7.50 mm Hg  1 atm = 760 mm Hg = kPa = 14.7 lb/in 2

Pressure Measurement  Manometers are used to measure pressure in open systems.  STP = Standard Temperature and Pressure  Gases are measured at STP, meaning kPa (also 760 mm of Hg or 1 atm) and 273K (0 o C)  Volumes are measured in Liters, m 3 or dm 3.