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Lesson 1: The Nature
of Gases
Lesson 1: The Nature
of Gases
UNIT 9 – GAS LAWSUNIT 9 – GAS LAWSChapter 13 and 14Chapter 13 and 14
Kinetic Molecular TheoryKinetic Molecular Theory Kinetic Molecular TheoryKinetic Molecular Theory
In order to understand gases you must understand the Kinetic Molecular Theory.
The KMT assumes the following concepts about an ideal gas:
Kinetic Molecular TheoryKinetic Molecular Theory Kinetic Molecular TheoryKinetic Molecular Theory
Particles in an ideal gas…• have no volume.• have elastic collisions. • are in constant, random, straight-
line motion.• don’t attract or repel each other.• have an avg. KE directly related to
Kelvin temperature.
Real GasesReal Gases Real GasesReal Gases
Real Gas behavior is most ideal…
• at low pressures
• at high temperatures
• in nonpolar atoms/molecule
Characteristics of Gases based on Characteristics of Gases based on KMTKMT Characteristics of Gases based on Characteristics of Gases based on KMTKMT
Particles in an real gas…
• have their own volume
• attract each other
Gases expand to fill any container.• random motion, no attraction
Characteristics of Gases based Characteristics of Gases based on KMTon KMT Characteristics of Gases based Characteristics of Gases based on KMTon KMT
Gases are fluids (like liquids).• no attraction
Gases have very low densities.• no volume = lots of empty space
Characteristics of Gases based on Characteristics of Gases based on KMTKMT Characteristics of Gases based on Characteristics of Gases based on KMTKMT
Gases can be compressed.• no volume = lots of empty space
Gases undergo diffusion & effusion.• random motion
PressurePressure PressurePressure
Fluids - Liquids
GasesBecause of their nature exert pressure in all directions
Gas pressure is the result of gas particles colliding with the walls of their container.
Measuring Gas PressureMeasuring Gas PressureMeasuring Gas PressureMeasuring Gas Pressure
Barometer• measures atmospheric pressure
Mercury Barometer
Aneroid Barometer
Measuring Gas PressureMeasuring Gas PressureMeasuring Gas PressureMeasuring Gas Pressure
Manometer• measures contained gas pressure
U-tube Manometer Bourdon-tube gauge
Measuring Gas PressureMeasuring Gas PressureMeasuring Gas PressureMeasuring Gas Pressure
All of these units are equivalentAll of these units are equivalent
101.325 kPa (kilopascal-SI Unit) is equal to
1 atm (atmosphere) is equal to
760 mm Hg is equal to
760 torr is equal to
14.7 psi (pounds per square inch)
Practice ConversionsPractice ConversionsPractice ConversionsPractice Conversions
Convert 0.927 atm to
• mmHg
• torr
• kPa
mmHgatm
mmHgatm 70552.704
1
760927.0
kPakPaatm
kPaatm 9.93928.93
1
325.101927.0
torratm
torratm 70552.704
1
760927.0
Practice ConversionsPractice ConversionsPractice ConversionsPractice Conversions Convert 148.6 kPa to atm
mmHg
torr
atmatm
kPa 467.1466568.1325.101
16.148
mmHgatm
mmHgx
kPa
atmkPa 111559.1114
1
760
325.101
16.148
torratm
torrx
kPa
atmkPa 111559.1114
1
760
325.101
16.148
STPSTP STPSTP
Standard Temperature & PressureStandard Temperature & Pressure
0°C 273 K
1 atm 101.325 kPa-OR-
STP
