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Published byArline June Skinner Modified over 9 years ago
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Unit 7.1: Measurements on Gases
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II) (7.1) Measurements on gases: a) Volume, amount, and temperature. i) A gas expands uniformly to fill any container in which it is placed ii) The volume of a gas is the volume of its container. 1) Can be expressed in liters, cubic centimeters or cubic meters 2) 1 L = 10 3 cm 3 = 10 -3 m 3 iii) The amount of matter is expressed in number of moles. (n) 1) Some cases, the mass is used instead. 2) Of course, these two quantities are related by molar mass
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II) (7.1) Measurements on gases: a) Volume, amount, and temperature. iv) The temperature: Ordinary Celsius is sufficient in most cases. 1) When physical behavior is involved: Use Kelvin 2) The conversion: T K = T C + 273.15 v) Pressure: 1) Force per unit area 2) The unit: The Pascal, which is one Newton of force on an area of one meter squared. 3) Atmospheric pressure: Atmospheric pressure: About 10 5 Pa or 100 kilopascals (kPa) 3) Conversion for Fahrenheit to Celsius: 4)
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II) (7.1) Measurements on gases: a) Volume, amount, and temperature. v) Pressure: 1) We use a mercury barometer to measure the atmospheric pressure. It looks like this: (Next slide)
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The pressure exerted by the mercury column equals the atmospheric pressure. Because of this device, pressure is often expressed in millimeters of mercury or mmHg 1 atmosphere of pressure (the normal pressure) is 760 mmHg.
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