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Applied Physics and Chemistry. Gases Lecture 1. Gases. Properties: No definite shape No definite volume Easily compressed Mixes completely with any other gas. Pressure. Kinetic molecular theory: All particles of matter are in constant motion
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Applied Physics and Chemistry Gases Lecture 1
Gases • Properties: • No definite shape • No definite volume • Easily compressed • Mixes completely with any other gas
Pressure • Kinetic molecular theory: • All particles of matter are in constant motion • Particles of a gas move fast and hit the container • Pressure: • Force of collisions of gas particles over an area of the container
Pressure! http://www.atmos.washington.edu/2005Q3/101/LINKS-html/MercuryBarometer.html • Atmosphere: • Due to the pull of gravity on gases • Measured by barometer • Evangelista Torricelli (1608-1647) • Measuring: • Mercury barometer • Anaeroid barometer http://www.free-online-private-pilot-ground-school.com/Aviation-Weather-Principles.html
Measuring Pressure • Units commonly used: • Torricelli (torr) • Millimeters of mercury (mmHg) • Atmosphere (standard atmosphere) (atmo) • SI: Pascal (Pa)
Pressure conversions • 1 atmosphere = • 760 mm Hg • 760 torr • 101 325 Pa • 101.325 kPa • 14.69 psi (ACK!) • Use conversion factors (carefully showing ALL WORK) to convert from one unit to another!
Example of conversion! • The pressure of air in a tire is recorded as 192 000 Pa. What is this pressure in atmospheres? • What we know: • P = 192 000 Pa • Conversion factors: • 1 atmo = 101 325 Pa • 192 000 Pa x 1 atmo = 1.895 atmo • 101 325 Pa
Another Example: • On a summer day in Breckenridge CO, the atmospheric pressure is 525 mm Hg. What is this pressure in atmospheres? • What we know: • P = 525 mm Hg • Conversion factor: • 1 atmo = 760 mm Hg • Do the math! • 525 mm Hg x 1 atmo = 0.69 atmo • 760 mm Hg