TEKS 9C: Describe the postulates of kinetic molecular theory. 1 Gases Properties of Gases Gas Pressure Copyright © 2009 by Pearson Education, Inc

TEKS 9C: Describe the postulates of kinetic molecular theory.

1

Gases Gases

Properties of Gases

Gas Pressure

Copyright © 2009 by Pearson Education, Inc.


2

Kinetic Theory of GasesKinetic Theory of Gases

A 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.



3

Properties That Describe a GasProperties That Describe a Gas

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



4

Gas pressure

• is a force acting on a specific area.

Pressure (P) = force

area

• has units of atm, mmHg, torr, lb/in.2, and kilopascals(kPa).

1 atm = 760 mm Hg (exact)

1 atm = 760 torr1 atm = 14.7 lb/in.2

1 atm = 101 325 Pa

1 atm = 101.325 kPa

Gas PressureGas Pressure


5

A. 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

Learning CheckLearning Check


6

SolutionSolutionA. 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 mmHg

2.00 atm x 760 mmHg = 1520 mmHg 1 atm


7

Atmospheric PressureAtmospheric Pressure

Atmospheric pressure

is the pressure exerted by a column of air from the top of the atmosphere to the surface of the Earth.



8

Altitude and Atmospheric PressureAltitude and Atmospheric Pressure

Atmospheric pressure

•is 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. Copyright © 2009 by Pearson Education, Inc.


9

BarometerBarometer

A barometer

•measures the pressure exerted by the gases in the atmosphere.

•indicates atmospheric pressure as the height in mm of the mercury column.



10

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) because

1) H2O is less dense than mercury.

2) H2O is heavier than mercury.

3) air is more dense than H2O.

Learning CheckLearning Check


11

A.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) because

1) H2O is less dense than mercury.

SolutionSolution


Temperature Conversion Equations

Temperature Conversion Equations

2 equations to use:

K = oC + 273 oC = K – 273


Practice Problem #1Practice Problem #1240oC = ____K

K = oC + 273

K = 240 + 273

K = 513


Practice Problem #2Practice Problem #2350K = ____ oC

oC = K – 273 oC = 350 – 273 oC = 77


Practice Problem #3Practice Problem #3510K = ____ oC

oC = K – 273 oC = 510 – 273 oC = 237


Practice Problem #4Practice Problem #420 oC = ____K

K = oC + 273

K = 20 + 273

K = 293


The EndThe End

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TEKS 9C: Describe the postulates of kinetic molecular theory. 1 Gases Properties of Gases Gas Pressure Copyright © 2009 by Pearson Education, Inc