Properties of Gases

Properties of Gases

Gas PressureA gas consists of small particles that:move rapidly in straight lines. have essentially no attractive (or repulsive) forces. are very far apart.have very small volumes compared to the volume of the container they occupy. have kinetic energies that increase with an increase in temperature.

GasesGases are described in terms of four properties: pressure (P), volume (V), temperature (T), and amount (n).

GasesGas pressure is a force acting on a specific area. Pressure (P) = force areahas units of atm, mmHg, torr, and kilopascals(kPa).

1 atm = 760 mm Hg (exact)1 atm = 760 torr1 atm = 101 325 Pa 1 atm = 101.325 kPa1 kPa = 7.501 mm HgGas Pressure2.5 atm = _______ mmHg

2.5 atm x 760 mm Hg = 1 atm Here is how you convert units2.5 atm = _______ mmHg

2.5 atm x 760 mm Hg = 1900 mm Hg 1 atm Here is how you convert unitsA. What is 475 mmHg expressed in atm? 1) 475 atm 2) 0.625 atm 3) 3.61 x 105 atm

B. The pressure in a tire is 2.00 atm. What is this pressure in mmHg? 1) 2.00 mmHg 2) 1520 mmHg 3)22 300 mmHg

7Learning CheckA. What is 475 mmHg expressed in atm?2) 0.625 atm475 mmHg x 1 atm = 0.625 atm 760 mmHg

B. The pressure in a tire is 2.00 atm. What is this pressure in mmHg?2) 1520 mmHg2.00 atm x 760 mmHg = 1520 mmHg 1 atm8SolutionAtmospheric PressureAtmospheric pressureis the pressure exerted by a column of air from the top of the atmosphere to the surface of the Earth.9Copyright 2009 by Pearson Education, Inc.

Sea level1 atm4 miles0.5 atm10 miles0.2 atmAltitude and Atmospheric PressureAtmospheric pressureis about 1 atmosphere at sea level. depends on the altitude and the weather.is lower at higher altitudes, where the density of air is less. is higher on a rainy day than on a sunny day.

11Copyright 2009 by Pearson Education, Inc.BarometerA barometermeasures the pressure exerted by the gases in the atmosphere.

indicates atmospheric pressure as the height in mm of the mercury column.12Copyright 2009 by Pearson Education, Inc.

A. The downward pressure of the Hg in a barometer is _____ than (as) the pressure of the atmosphere. 1) greater 2) less 3) the same

B. A water barometer is 13.6 times taller than a Hg barometer (DHg = 13.6 g/mL) because1) H2O is less dense than mercury.2) H2O is heavier than mercury. 3) air is more dense than H2O.13Learning CheckA.The downward pressure of the Hg in a barometer is 3) the same (as) the pressure of the atmosphere.

B. A water barometer is 13.6 times taller than a Hg barometer (DHg = 13.6 g/mL) because1) H2O is less dense than mercury. 14Solution2 equations to use:

K = oC + 273 oC = K 273Temperature Conversion Equations

240oC = ____K

Practice Problem #1

240oC = ____K

K = oC + 273K = 240 + 273K = 513

Practice Problem #1

350 K = ____ oC

Practice Problem #2

350 K = ____ oC

oC = K 273oC = 350 273oC = 77

Practice Problem #2

510 K = ____ oC

Practice Problem #3

510 K = ____ oC

oC = K 273oC = 510 273oC = 237

Practice Problem #3

20 oC = ____K

Practice Problem #4

20 oC = ____K

K = oC + 273K = 20 + 273K = 293

Practice Problem #4