10 - Gases and the Atmosphere

# 10 - Gases and the Atmosphere - Chapter 10: Gases and the...

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Chapter 10: Gases and the Atmosphere transparent, some are colored expand to fill all space available (mobile) mix together physically in any proportions densities are variable because volume is variable 10.1The Atmosphere nitrogen and oxygen make up most of the atmosphere, small quantities of other molecules (i.e., noble gases); oxygen is highly combustible but is diluted with nitrogen (unreactive) in the atmosphere ppm and ppb are used to give ratio of molecules of one kind to another; 10 ppm SO 2 is for every 1 million molecules of air, 10 are SO 2 The Troposphere and the Stratosphere o troposphere – closest to earth; mixing of air, variation in moisture and temperature throughout earth o stratosphere – next layer, low pressure 10.2Properties of Gases can be compressed, gas that occupies less volume than noncompressed air exert pressure on surroundings expand into whatever volume is available mix completely with one another described in terms of their temperature, pressure, volume occupied, and amount (number of molecules or moles) of gas present Gases Exert Pressure o pressure = force per unit area o will exert pressure on every surface it contacts, no matter what the direction of contact o force is measured in Newtons (N) and pressure in pascal (Pa) o atmospheric pressure can be measured with a barometer in mmHg o 1 Pa = 1 N/m 2 o 1 atm = 1.01325 x 10 5 Pa = 760 torr = 760 mmHg = 1.01325 bar o any liquid can be used in a barometer, but height of column depends on density of liquid 10.3Kinetic-Molecular Theory KMT applies properties of liquids and solids to gases gas consists of tiny molecules in constant, rapid, random motion pressure of gas results from bombardment of walls by rapidly moving gas molecules KMT states o 1) gas is composed of molecules whose size is much smaller than distances between them; so

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## 10 - Gases and the Atmosphere - Chapter 10: Gases and the...

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