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Gases

Gases. Chapter 12. What elements exist as a gas at room temperature?. H 2 N 2 O 2 F 2 Cl 2 He Ne Ar Kr Xe Rn. 1. Gases have very low densities. Solids and liquids have much higher density. Gas particles are spread out. 2. Gases have mass .

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Gases

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  1. Gases Chapter 12

  2. What elements exist as a gas at room temperature? H2 N2 O2 F2 Cl2 He Ne Ar Kr Xe Rn

  3. 1. Gases have very low densities. • Solids and liquids have much higher density. • Gas particles are spread out.

  4. 2. Gases have mass. • A filled balloon is heavier than an empty balloon. • 3. Gases are the most compressible state of matter. • Gas particles can be squished closer together.

  5. 4. Gases take the shape and volume of their containers. • Gases fill the entire space they are in. • 5. Different gases will mix evenly and completely called diffusion. • You can smell brownies baking in the oven when in a different room.

  6. 6. Gases exert pressure. • You can feel the wind hit your face. • 7. The pressure of a gas depends on its temperature. • Temperature is a measure of kinetic energy. The more energy, the more force the gases hit a surface, the higher the pressure.

  7. Gas Measurements

  8. Measuring Gases

  9. Remember: 1 mol = 6.02 x 1023 particles 1 mL = 1 cm3 K = oC + 273

  10. K = 0C + 273 273 K = 0 0C 373 K = 100 0C Convert the following temp into Kelvin: 25 0C 232 0C

  11. Units of Pressure

  12. Barometer Measuring Gas Pressure • Atmospheric pressure is measured by a barometer. • The pressure is then read on the column. 760 mm

  13. Measuring Gas Pressure • At sea level, the atmosphere keeps the mercury in a barometer at an average height of 760 mm (equals 1 atmosphere, atm.) • One millimeter of mercury is also equal to a torr, after Evangelista Torricelli, the Italian physicist who invented the barometer.

  14. Measuring Gases 10 miles 0.2 atm 4 miles 0.5 atm Sea level 1 atm

  15. Scientists have specified a set of standard conditions called standard temperature and pressure • STP = 0°C and 1 atm.

  16. The Gas Laws

  17. Pressure and Volume Relationship V decreases As P (h) increases

  18. Constant temperature Constant amount of gas This is called: BOYLE’S LAW • pressure and volume are inversely related Pi x Vi = Pf x Vf

  19. 726 mmHg x 946 mL Pi x Vi = 154 mL Vf A sample of chlorine gas occupies a volume of 946 mL at a pressure of 726 mmHg. What is the pressure of the gas (in mmHg) if the volume is reduced at constant temperature to 154 mL? Vi = 946 mL Pi = 726 mmHg Pf = ? Vf = 154 mL Pi x Vi = Pf x Vf Pf = = 4460 mmHg

  20. Temperature and Volume Relationship As T increases V increases

  21. Constant pressure Constant amount of gas This is called: CHARLES’ LAW • temperature and volume are directly related Vi = Vf Ti Tf Temperature must be in Kelvin T (K) = (0C) + 273

  22. 1.54 L x 398 K Vf x Ti = 3.20 L Vi A sample of carbon monoxide gas occupies 3.20 L at 125 0C. At what temperature will the gas occupy a volume of 1.54 L if the pressure remains constant? Vi = 3.20 L Vf = 1.54 L Ti = 125oC 398 K Tf = ? Vi = Vf Ti Tf Tf = = 192 K

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