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Pressure and Temperature William Thomson Lord Kelvin

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CA Standards

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Measuring Pressure The first device for measuring atmospheric pressure was developed by Evangelista Torricelli during the 17 th century. The device was called a barometer Baro = weight Meter = measure

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An Early Barometer The normal pressure due to the atmosphere at sea level can support a column of mercury that is 760 mm high.

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Pressure is caused by the collisions of molecules with the walls of a container is caused by the collisions of molecules with the walls of a container is equal to force/unit area is equal to force/unit area can be measured using a variety of units can be measured using a variety of units

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Pressure UnitSymbolDefinition/Relationship Millimeter of mercury mm HgPressure that supports a 1 mm column of mercury in a barometer Torrtorr1 torr = 1 mm Hg PascalPaSI pressure unit 1 Pa = 1 newton/meter 2 AtmosphereatmAverage atmospheric pressure at sea level and 0 C Pressure is the force created by the collisions of molecules with the walls of a container

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Standard Pressure 760 torr 760 mm Hg (millimeters of mercury) 760 mm Hg (millimeters of mercury) kPa (kilopascals) kPa (kilopascals) 1 standard atmosphere (atm) 1 standard atmosphere (atm)

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Converting Pressure Units Gas law problems involving pressure require that the pressure be in the SAME UNITS! 1 atm = kPa = 760 mm Hg Converting kPas to atms x atms = ____ kPas 1atm101.3 kPa 1atm101.3 kPa Converting kPas to mm Hg x mm Hg = ____ kPas 760 mm Hg kPa

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Converting Pressure Units A gas sample has a pressure of mmHg. What is the pressure of this gas sample in atmospheres and in kilopascals? 1 atm = kPa = 760 mm Hg Converting mm Hg to atms x atms = 800 mm Hg 1atm 760 mm Hg 1atm 760 mm Hg Converting mm Hg to kPas x kPas = 800 mm Hg kPa760 mm Hg x = atmx = kPa

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Converting Pressure Units A tank of oxygen is under a pressure of about 4.00 x 10 3 kPa. Express this pressure in millimeters of mercury. 1 atm = kPa = 760 mm Hg Converting kPas to mm Hg x mm Hg= 4 x 10 3 kPas 760 mm Hg101.3 kPa x = 3.00 x 10 4 mm Hg

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Air Pressure has many applications (in real life!) Heres one of those applications ! applications

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The Kelvin Scale

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Standard Temperature Standard Temperature equals: 273 Kelvin (273 K) 273 Kelvin (273 K) 0 C 0 C

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Converting Celsius to Kelvin Gas law problems involving temperature require that the temperature be in KELVINS! Kelvins = C °C = Kelvins - 273

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Standard Temperature and Pressure STP Either of these: 273 Kelvin (273 K) 273 Kelvin (273 K) 0 C 0 C Either of these: 273 Kelvin (273 K) 273 Kelvin (273 K) 0 C 0 C And any one of these: 1 atm kPa kPa 760 mm Hg 760 mm Hg 760 torr 760 torr And any one of these: 1 atm kPa kPa 760 mm Hg 760 mm Hg 760 torr 760 torr

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