Physical Characteristics of Gases
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Transcript of Physical Characteristics of Gases
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Physical Characteristics of
Gases
Pressure
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Objectives
1. Define pressure and relate it to force
2. Describe how pressure is measured.
3. Convert units of pressure.
4. State the standard conditions of temperature and pressure.
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Pressure
To adequately describe a gas, you must know…• Volume• Temperature• Number of particles• Pressure
area
force Pressure
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Atmospheric PressureThe gases that make up the
atmosphere exert pressure on their surroundings. It is a result of:
1. Collisions between gas particles.
2. The weight of the atmospheric gases above the earth’s surface.
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Measuring Pressure • Atmospheric pressure is
measured using a barometer.
• Atmospheric pressure depends on elevation and weather.
• Normal atmospheric pressure at sea level: 760 mm Hg
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Measuring Pressure• A manometer can be
used to measure the pressure of an enclosed gas.
• The pressure is measured relative to atmospheric pressure.
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Units of PressureUnit Symbol Std. Atmospheric
pressure
Millimeters of Hg mm Hg 760
Centimeters of Hg cm Hg 76
Inches of Hg in. Hg 29.92
Torr Torr 760
Pascals (N/m2) Pa 101,325
Atmospheres atm 1
Pounds per square inch psi 14.69
bars bar 1.01325
•The Pascal is the SI unit
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Pressure Conversions• Convert 35 psi into units of atmospheres.atm
psi1
35 atm
psi
atmpsi 4.2
69.14
135
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Standard Temperature and Pressure• Conditions used by scientists for comparison.
1 atm
0oC