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PROPERTIES OF GASES II

PROPERTIES OF GASES II. PRESENTATION 2 2014. Properties of Gases. Gases have mass – find mass of empty balloon and filled balloon It is easy to compress gases – squeezed gas reduces its volume; car air bags Gases fill their containers completely –

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PROPERTIES OF GASES II

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  1. PROPERTIES OF GASESII PRESENTATION 2 2014

  2. Properties of Gases Gases have mass – find mass of empty balloon and filled balloon It is easy to compress gases – squeezed gas reduces its volume; car air bags Gases fill their containers completely – Different gases can move through each other quite rapidly – diffusion (body spray, body gas, etc) Gases exert pressure – ear drums “popping”, filled balloon The pressure of a gas depends on its temperature↑ temp = ↑ pressure; ↓ temp = ↓ pressure

  3. Properties of Gases and the Air we Breathe • Main Ideas (in no order): • Atmospheric Pressure • Volume • Temperature • Kinetic Molecular Theory • Composition of Air • How will we do it: • Notes • Labs and Activities • Worksheets • Practice Problems and Questions

  4. MEASURING GASES • Four Variables: • Amount of gas • Volume • Temperature • Pressure

  5. AMOUNT OF GAS (n) Quantity of gas in a given sample is expressed in terms of moles of gas n =mass = m (g)____ molar mass M (g/mol) One mole of NaCl, = mass of 58.45 g. One mole of the liquid, = mass of 18.0 g and occupies a volume of 18.0 mL. One mole of the gas, = mass of 32.0 g and occupies a balloon whose diameter is 35 cm

  6. VOLUME (V) • Gas uniformly fills any container in which it is placed • Volume of gas = volume of its container • Metric unit = L • 1 L = 1000 cm3

  7. TEMPERATURE (T) • Measured with thermometer in degree Celsius (˚C) • Must be converted to Kelvin temp scale • No negative temps • T (K) = T (˚C) + 273

  8. PRESSURE (P) Outward force of gas spread over the area of the container is called pressure P = Force Area Pressure = Pascal (Pa)

  9. ATMOSPHERIC PRESSURE Gases of atmosphere also exert pressure on everything come into contact with (gas) density = Mass (of gas) Volume P = m V Atmospheric Pressure decreases with height

  10. Pressure of Atmosphere Can Crushing http://www.youtube.com/watch?v=QVayky_b-6U 55 Gallon Drum http://www.youtube.com/watch?v=Uy-SN5j1ogk

  11. Pressure Measuring Devices • Weather Prediction • Barometer • http://www.youtube.com/watch?v=jmQ8FWnM0fA&list=RDQeAp3CuGjk8 • Regulation of gas flow • http://www.youtube.com/watch?v=QeAp3CuGjk8

  12. Units of Pressure 1 atmosphere (atm) = 101,325 Pa 1 atm = 760 mm Hg = 760 torr 1 atm = 14.70 lb/in2 1 bar = 100,000 Pa = 0.9869 atm

  13. Sample Problems Mercury (Hg) column in barometer is 745 mm above the mercury reservoir at the bottom. What is the atmospheric pressure in pascals? 745 mm Hg x 101,325 Pa = 99,300 Pa 760 mm Hg

  14. Practice Problem The air pressure inside the cabin of an airplane is 8.3 lb/in2 What is this pressure in atmosphere units?

  15. Practice Problem 2 Pressure is considered the most accurate measure of storm strength, with lower pressure indicating a stronger storm. One of the lowest recorded pressures in the Western Hemispheres is 88.86 kPa. How high a column of mercury would be balanced by this atmospheric pressure?

  16. Pressure Conversions STP meansstandard temperature and pressure 1 standardatmosphere = 1.000 atm= 760.0 mm Hg= 760.0 torr =101,325 Pa = 14.69 psi ***all of these equal each other!*** Temperature: 0 ˚C or 273 K

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