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## Pressure and Temperature

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**Pressure and Temperature**William Thomson “Lord Kelvin”**Measuring Pressure**The first device for measuring atmospheric pressure was developed by Evangelista Torricelli during the 17th century. The device was called a “barometer” • Baro = weight • Meter = measure**An Early Barometer**The normal pressure due to the atmosphere at sea level can support a column of mercury that is 760 mm high.**is caused by the collisions of molecules with the walls of**a container is equal to force/unit area can be measured using a variety of units Pressure**Pressure**• Pressure is the force created by the collisions • of molecules with thewalls of a container**760 torr**760 mm Hg (millimeters of mercury) 101.3 kPa (kilopascals) 1 standard atmosphere (atm) Standard Pressure**Converting Pressure Units**Gas law problems involving pressure require that the pressure be in the SAME UNITS! 1 atm = 101.3 kPa= 760 mm Hg Converting kPas to atms x atms= ____kPas 1atm 101.3 kPa Converting kPas to mm Hg x mm Hg= ____kPas 760 mm Hg 101.3 kPa**Converting Pressure Units**1 atm = 101.3 kPa= 760 mm Hg A gas sample has a pressure of 800.0 mmHg. What is the pressure of this gas sample in atmospheres and in kilopascals? Converting mm Hg to atms x atms= 800 mm Hg 1atm 760 mm Hg Converting mm Hg to kPas x kPas = 800 mm Hg 101.3 kPa 760 mm Hg x = 1.053 atm x = 106.6 kPa**Converting Pressure Units**1 atm = 101.3 kPa= 760 mm Hg A tank of oxygen is under a pressure of about 4.00 x 103kPa. Express this pressure in millimeters of mercury. Converting kPas to mm Hg x mm Hg = 4 x 103kPas 760 mm Hg 101.3 kPa x = 3.00 x 104 mm Hg**has many applications (in real life!)**Here’s one of those applications ! Air Pressure**Standard Temperature**• Standard Temperature equals: • 273 Kelvin (273 K) • 0 C**Converting Celsius to Kelvin**Gas law problems involving temperature require that the temperature be in KELVINS! Kelvins = C + 273 °C = Kelvins - 273**Either of these:**• 273 Kelvin (273 K) • 0 C Standard Temperature and Pressure“STP” • And any one of these: • 1 atm • 101.3 kPa • 760 mm Hg • 760 torr