1 Behavior of GASES
2 Physical Properties Gases consist of small particles that have massIt is easy to compress gases Gases fill their container completely Different gases move through each other quite rapidly. The movement of one substance through another is called diffusion.
3 Physical Properties Gases exert pressure by colliding with the walls of the container. The pressure of a gas depends on its temperature (T). Temp Pressure Temp Pressure
4 Kinetic-Molecular TheoryTo apply the Kinetic-Molecular Theory to gases, we have to make the following assumptions about gases. A gas consists of very small particles that have mass. The particles in a gas are separated from each other by relatively large distances. Gas particles are in constant rapid motion.
5 Kinetic-Molecular TheoryCollisions of gas particles with each other or with the walls of the container are perfectly elastic. That means no energy is lost during the collision and the particles do not slow down. The average kinetic energy (KE) of gas particles depends only on the temperature (T) of the gas. T KE T KE Gas particles exert no force on one another. (no attraction & no repulsion)
6 Measuring Pressure of Gasesamount of gas (n) mole(mol) volume (V) liter(L), milliliter(mL), cubic centimeter(cc) temperature (T) Kelvin(K), Celsius(ºC) pressure (P) atmosphere(atm) kilopascal (kPa) mm Hg torr
7 Measuring Pressure of GasesStandard Temperature and Pressure (STP) (Reference Table A) Temperature => 0ºC = 273K Pressure => 1 atm = kPa = 760 mm Hg = 760 torr
8 Measuring Pressure of GasesConvert the following pressures to the unit indicated by the table. Unit Equalities for pressure conversion factors 1.0 atm = kPa = 760 mm Hg = 760 torr 101.3 kPa = 14.7 psi 760 mm Hg = inches Hg
9 Measuring Pressure of GasesConvert the following pressures to the unit indicated by the table. Unit Equalities for pressure conversion factors 1.0 atm = kPa = 760 mm Hg = 760 torr 101.3 kPa = 14.7 psi 760 mm Hg = inches Hg Do practice conversion problems on next page first ->
10 1.0 atm = kPa = 760 mm Hg = 760 torr Convert the following pressures to the unit indicated. 1) The air pressure for a certain tire is 109 kPa. What is the pressure in atmospheres (atm)? 2) The air pressure inside a submarine is 0.62 atm. What would be the height of a column of mercury for this pressure (mmHg)? 3) The weather news gives the atmospheric pressure as mm Hg. What would this pressure be in units of atmospheres (atm)? 4) An experiment at Sandia National Labs in Mexico is performed at an atmospheric pressure of atm. What is the pressure in kiloPascals (kPa)?
11 1.0 atm = kPa = 760 mm Hg = 760 torr Convert the following pressures to the unit indicated. The air pressure for a certain tire is 109 kPa. What is the pressure in atmospheres (atm)? [1.08 atm] 2) The air pressure inside a submarine is 0.62 atm. What would be the height of a column of mercury for this pressure (mmHg)? [471 mm Hg = 460 mm Hg] 3) The weather news gives the atmospheric pressure as mm Hg. What would this pressure be in units of atmospheres (atm)? [1.06 atm] 4) An experiment at Sandia National Labs in Mexico is performed at an atmospheric pressure of atm. What is the pressure in kiloPascals (kPa)? [ kPa]
12 Millimeters of Mercury1.0 atm = kPa = 760 mm Hg = 760 torr Millimeters of Mercury (mm Hg) kiloPascals (kPa) atmospheres (atm) 760 mm Hg 101.3 kPa 1.0 atm 738 mm Hg .88 atm 98.7 kPa 2.0 atm 50.65 kPa 775 mm Hg
13 Measuring Pressure of GasesAtmospheric Pressure - the pressure exerted by the air in the atmosphere. BN - Atmospheric Pressure 5:34 Atmospheric pressure varies with altitude.
14 Measuring Pressure of GasesThe lower the altitude the longer and heavier the column of air, and the higher the atmospheric pressure. Air has mass and it is attracted to the earth by gravity. column of air Force of gravity Earth Atmospheric Pressure-force exerted by the weight of the air How heavy is air? 3:18 Barometers and an open-ended manometers are devices used to measure pressure.
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16 Mount Everest (also known in Nepal as Sagarmatha and in Tibet as Chomolungma) is the Earth's highest mountain. It is located in the Mahalangur section of the Himalayas. Its peak is 8,848 metres (29,029 ft) above sea level
17 Torricelli's BarometerNarrated Cartoon description of early Barometer 04:45
18 Measuring Pressure of GasesFigure p386 Barometer - used to measure atmospheric pressure Atmospheric Pressure Glass tube mm Hg Pool of Hg Mercury Barometer 1:35
19 Measuring Pressure of GasesFigure p386 Barometer - used to measure atmospheric pressure Atmospheric Pressure Glass tube The heavier the column of air the higher the Hg is pushed up into the glass tube and the higher the pressure. mm Hg Pool of Hg
20 Measuring Pressure of GasesAtmospheric Pressure - High Higher the level of mercury in the glass tube mm Hg
21 Measuring Pressure of GasesAtmospheric Pressure - Low Lower the level of mercury in the glass tube mm Hg experiments with the liquid metal mercury IV 2:14
22 The most common type barometer used in homes is the aneroid barometerBarometer that measures atmospheric pressure via the expansion and contraction of a sealed hollow cell which is partially depleted of air.
23 Measuring Pressure of Gasesaneroid barometer Inside this instrument is a small, flexible metal capsule called an aneroid cell. In the construction of the device, a vacuum is created inside the capsule so that small changes in outside air pressure cause the capsule to expand or contract. The size of the aneroid cell is then calibrated and any change in its volume is transmitted by springs and levers to an indicating arm that points to the corresponding atmospheric pressure.
24 8 (score out of 10)
25 Measuring Pressure of Gases.): Measuring Pressure of Gases Manometer A manometer is an device employed to measure pressure. There are a variety of manometer designs. A simple, common design is to seal a length of glass tubing and bend the glass tube into a U-shape. The glass tube is then filled with a liquid, typically mercury, so that all trapped air is removed from the sealed end of the tube. The glass tube is then positioned with the curved region at the bottom. The mercury settles to the bottom (see the picture at the left).