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

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

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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)

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