1. Barometer Vacuum Height of column 29.92 in. (76 cm) Air pressure Mercury

2. Barometer Vacuum Height of column 29.92 in. (76 cm) Air pressure Mercury

3. How to Measure Pressure Aneroid Barometer Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Barometer –measures atmospheric pressure vacuum P atm P Hg

4. barometer barometer: device to measure air pressure air pressure vacuum mercury (Hg)

5. Barometer Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 401 Empty space (a vacuum) Hg Weight of the mercury in the column Weight of the atmosphere (atmospheric pressure)

6. Barometer Mercury filled 760 mm = 1 atm Water filled 10400 mm = 1 atm The barometer measures air pressure Water column (34.0 ft. high or 10.4 m) Atmospheric pressure Mercury column (30.0 in. high or 76 cm )

7. Barometers Mount Everest Sea level On top of Mount Everest Sea level fraction of 1 atm average altitude (m)(ft) 100 1/25,48618,000 1/38,37627,480 1/1016,13252,926 1/10030,901101,381 1/100048,467159,013 1/1000069,464227,899 1/10000096,282283,076

8. Boiling vs. Evaporation Boiling point: atmospheric pressure = vapor pressure Evaporation: molecules go from liquid to gas phase Evolutionary process - slow Revolutionary process - fast Lyophilization – freeze drying AIR PRESSURE 15psi VAPOR PRESSURE 15 psi liquid gas

9. Boiling Point on Mt. Everest Water exerts a vapor pressure of 101.3 kPa at a temperature of 100 o C. This is defined as its normal boiling point: ‘vapor pressure = atmospheric pressure’ x kPa = 253 mm Hg (101.3 kPa) = 33.7 kPa (760 mm Hg)

10. Boiling Point on Mt. Everest Water exerts a vapor pressure of 101.3 kPa at a temperature of 100 o C. This is defined as its normal boiling point: ‘vapor pressure = atmospheric pressure’ 101.3 93.3 80.0 66.6 53.3 40.0 26.7 13.3 0102030405060708090100 61.3 o C78.4 o C100 o C chloroform ethyl alcohol water Temperature ( o C) Pressure (KPa) On top of Mt. Everest 760 mm Hg x kPa = 253 mm Hg 101.3 kPa =33.7 kPa

11. 760 mm Hg Boiling Point on Mt. Everest Water exerts a vapor pressure of 101.3 kPa at a temperature of 100 o C. This is defined as its normal boiling point: ‘vapor pressure = atmospheric pressure’ 101.3 93.3 80.0 66.6 53.3 40.0 26.7 13.3 0102030405060708090100 61.3 o C78.4 o C100 o C chloroform ethyl alcohol water x kPa = 253 mm Hg 101.3 kPa =33.7 kPa Temperature ( o C) Pressure (KPa)