I. Physical Properties (p. 403 - 412) Ch. 12 & 13 – Gases I. Physical Properties (p. 403 - 412)

A. Kinetic Molecular Theory The kinetic molecular theory describes the behavior of matter in terms of particles in motion. Objects in motion have energy called kinetic energy

A. Kinetic Molecular Theory Particles in an ideal gas… have no volume have elastic collisions are in constant, random, straight-line motion don’t attract or repel each other have an avg. KE directly related to Kelvin temperature

B. Real Gases Particles in a REAL gas… have their own volume attract each other Gas behavior is most ideal… at low pressures at high temperatures in nonpolar atoms/molecules

C. Characteristics of Gases Gases expand to fill any container random motion, no attraction Gases are fluids (like liquids) no attraction Gases have very low densities no volume = lots of empty space C. Johannesson

C. Characteristics of Gases Gases can be compressed. no volume = lots of empty space Gases undergo diffusion & effusion. random motion

D. Describing Gases Gases can be described by their: Temperature K Pressure Volume Number of molecules/moles K atm L #

E. Temperature Always use absolute temperature (Kelvin) when working with gases. ºF ºC K -459 32 212 -273 100 273 373 K = ºC + 273 C. Johannesson

Which shoes create the most pressure? F. Pressure Which shoes create the most pressure? Why?

F. Pressure exact height of the Hg depends on atmospheric pressure Barometer measures atmospheric pressure = result of mass of air pulled toward Earth by force of gravity exact height of the Hg depends on atmospheric pressure usually measured in mm Hg

F. Pressure Manometer measures contained gas pressure Difference in height in two arms of U-tube is measure of pressure of gas sample measured in various different units

Measuring Pressure Vacuum Gas Pressure

Measuring Pressure Vacuum Gas Pressure

Measuring Pressure Vacuum Gas Pressure Manometer

F. Pressure KEY EQUIVALENT UNITS 101.325 kPa (kilopascal) 1 atm 760 mm Hg 760 torr 14.7 psi

Standard Temperature & Pressure G. STP STP Standard Temperature & Pressure 0°C 273 K 1 atm 101.325 kPa -OR-

H. Pressure Problem 1 The average pressure in Denver, Colorado, is 0.830 atm. Express this in (a) mm Hg and (b) kPa. 760 mm Hg (a) 0.830 atm = 631 mm Hg 1 atm 101.325 kPa (b) 0.830 atm = 84.1 kPa 1 atm

H. Pressure Problem 2 Convert a pressure of 1.75 atm to kPa and mm Hg. (a) 1.75 atm = 177 kPa 1 atm 760 mm Hg (b) 1.75 atm = 1330 mm Hg 1 atm

H. Pressure Problem 3 Convert a pressure of 570. torr to atmospheres and kPa. 1 atm (a) 570 torr = .750 atm 760 torr 101.325 kPa (b) 570 torr = 76.0 kPa 760 torr