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Pressure and Temperature

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  1. Pressure and Temperature William Thomson “Lord Kelvin”

  2. 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

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

  4. 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

  5. Pressure • Pressure is the force created by the collisions • of molecules with thewalls of a container

  6. 760 torr 760 mm Hg (millimeters of mercury) 101.3 kPa (kilopascals) 1 standard atmosphere (atm) Standard Pressure

  7. 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

  8. 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

  9. 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

  10. has many applications (in real life!) Here’s one of those applications ! Air Pressure

  11. The Kelvin Scale

  12. Standard Temperature • Standard Temperature equals: • 273 Kelvin (273 K) • 0 C

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

  14. 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