To learn about atmospheric pressure and how barometers work To learn the units of pressure To understand how the press - PowerPoint PPT Presentation

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To learn about atmospheric pressure and how barometers work To learn the units of pressure To understand how the press PowerPoint Presentation
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To learn about atmospheric pressure and how barometers work To learn the units of pressure To understand how the press

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To learn about atmospheric pressure and how barometers work To learn the units of pressure To understand how the press
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To learn about atmospheric pressure and how barometers work To learn the units of pressure To understand how the press

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  1. Objectives • To learn about atmospheric pressure and how barometers work • To learn the units of pressure • To understand how the pressure and volume of a gas are related • To do calculations involving Boyle’s Law • To learn about absolute zero • To understand how the volume and temperature of a gas are related • To do calculations involving Charles’s Law • To understand how the volume and number of moles of a gas are related • To do calculations involving Avogadro’s Law

  2. Gases Exert Pressure: What is Pressure? • Pressure is defined as the force exerted divided by the area it acts over • Pressure = Force/Area • Typical Units are lbs/in2 or kg/m2 • If a woman changes her shoes from sneakers to high heels does she exert a different pressure on the floor? • Where does the pressure that a gas exerts come from?

  3. A. Pressure Measuring Atmospheric Pressure • Barometer – device that measures atmospheric pressure • Invented by Evangelista Torricelli in 1643

  4. A. Pressure • Atmospheric Pressure • Changing weather conditions

  5. A. Pressure • Atmospheric Pressure • Changing altitude Record Sky Dive

  6. A. Pressure • Units of Pressure 1 standard atmosphere = 1.000 atm = 760.0 mm Hg = 760.0 torr = 101,325 Pa (1Pa = 1 N/m2) The air pressure on Everest is 0.3 atm. What is that measured using the other units?

  7. A. Pressure • Measurement of Pressure • A manometer measures the pressure of a gas in a container • Gas pressure is the force exerted by the collisions of gas particles with a surface

  8. B. Pressure and Volume: Boyle’s Law • Robert Boyle’s experiment • Around 1660 Boyle studied the relationship between the pressure and volume of a gas

  9. B. Pressure and Volume: Boyle’s Law Draw a graph of V vs. P and also V vs. 1/P

  10. B. Pressure and Volume: Boyle’s Law • Graphing Boyle’s results

  11. B. Pressure and Volume: Boyle’s Law • This graph has the shape of half of a hyperbola with an equationPV = k or V = k/P • Volume and pressure are inversely proportional. • If one increases the other decreases.

  12. B. Pressure and Volume: Boyle’s Law Another way of stating Boyle’s Law is P1V1 = P2V2 (constant temperature and amount of gas) (WOC P480 Q7-10)

  13. What makes this balloon fly? Balloon Launch

  14. C. Volume and Temperature: Charles’s Law • Graphing data for several gases

  15. C. Volume and Temperature: Charles’s Law • It is easier to write an equation for the relationship if the lines intersect the origin of the graph. • Use absolute zero for the temperature

  16. C. Volume and Temperature: Charles’s Law • These graphs are lines with an equation V = bT (where T is in kelvins) • Volume and temperature are directly proportional. • If one increases the other increases by the same proportion. • Another way of stating Charles’s Law is V1 = V2 • T1 T2 • (constant pressure and amount of gas)

  17. D. Volume and Moles: Avogadro’s Law

  18. D. Volume and Moles: Avogadro’s Law • Volume and moles are directly proportional. • If one increases the other increases • V = an • constant temperature and pressure • Another way of stating Avogadro’s Law is V1 = V2 • n1 n2 • (constant temperature and pressure)