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Pressure & Temperature

Pressure & Temperature. The weight of Earth’s atmosphere above us exerts a pressure on us. In a way, we live at the bottom of an ocean of air. Atmospheric Pressure. Atmospheric pressure changes with altitude and with weather conditions.

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Pressure & Temperature

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  1. Pressure & Temperature

  2. The weight of Earth’s atmosphere above us exerts a pressure on us. In a way, we live at the bottom of an ocean of air.

  3. Atmospheric Pressure Atmospheric pressure changes with altitude and with weather conditions. Standard pressure is the average pressure of our atmosphere at sea level. 1.0 atmosphere 760 mm Hg (mercury) 14.7 lb/in2 (psi) 101.325 kilopascals

  4. A Mercury Barometer No pressure (vacuum) Mercury Hg Atmospheric Pressure 760 mm Hg = Standard Pressure 1.0 atmosphere

  5. If the weather changes, or if the pressure is measured at higher elevations… Pressure is measured by how far it pushes mercury up a tube. Atmospheric Pressure decreases 725 mm Hg

  6. American System Pressure is measured in psi (lb/in2) The weight of the atmosphere is 14.7 pounds on every square inch area. 14.7 pounds 14.7 pounds That’s about 4 or 5 of your Chemistry books. 14.7 pounds 1 inch 1 inch

  7. International System (SI) The international way of measuring pressure uses Newtons per square meter. mass x gravity = Newton (force) Newtons/m2= Pascal 101,325 Newtons/m2 = 101,325 Pascals 101.325 kiloPascals > 10 tons 101.325 kPa 1 meter 1 meter

  8. Standard Pressure 1.0 atmosphere (atm) 760 mm Hg = 760 torr 14.7 lb/in2 (psi) 101.325 kiloPascals (kPa) Pressure can be measured in different units. Meteorologists use another way for measuring pressure (like in hurricanes). 1013 millibars is standard pressure.

  9. If the recommended tire pressure is 32 psi, (a)What is the equivalent pressure in atmospheres? (b) in kPa? 1.0 atmosphere 760 mm Hg 14.7 lb/in2 (psi) 101.325 kilopascals atm More than twice atmospheric pressure. 1.0 x ________ 32 psi = 2.18 atm psi 14.7 kPa 101.325 x __________ 32 psi = 220 kPa psi 14.7

  10. Manometer 750 mm Hg

  11. Manometer 750 mm Hg 750 mm Hg 950 mm Hg + 200 mm 200 mm

  12. Manometer 750 mm Hg 650 mm Hg 750 mm Hg - 100 mm 100 mm

  13. Manometer 765 mm Hg 765 mm Hg 915 mm Hg ? mm Hg + 150 mm 150 mm

  14. 273o Celsius Kelvin water boils 100oC + 273 = ? K 373 K oC + 273 = Kelvin 25oC + 273 = 298 K ? K To change Celsius to Kelvin, add 273 water freezes ? K 273 K 0oC + 273 = -273 oC + 273 = 0 Kelvin absolute zero

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