I. Physical Properties (p. 303 - 312)

1
I. Physical Properties(p. 303 - 312)

• Ch. 10 11 - Gases

2
The Kinetic-Molecular Theory of Matter

• Used to explain the properties of gases, liquids
  and solids in terms of
• 1) Energy of particles
• 2) Forces acting between particles.
• Kinetic Theory is based on the idea that
  particles of matter are in constant motion and
  that this motion has consequences.

3
The Kinetic-Molecular Theory of Gases

• Ideal Gas - Imaginary gas that conforms perfectly
  to all assumptions of the Kinetic Theory.

4
A. Kinetic Molecular Theory

• Particles in an ideal gas
• have no volume.
• have elastic collisions.
• are in constant, random, straight-line motion.
• dont attract or repel each other.
• have an avg. KE directly related to Kelvin
  temperature.

5
B. Real Gases

• Particles in a REAL gas
• have their own volume
• attract each other, therefore collisions are not
  elastic (slowed down)
• Avg KE still directly related to Kelvin Temp

6
Real gas

• Gas behavior is most ideal
• at low pressures
• at high temperatures
• in nonpolar atoms/molecules

7
The Kinetic Theory and the Nature of Gases

• The Kinetic Theory accounts for the following
  physical properties of gases
• Expansion - gases do not have a definite shape
  nor definite volume, they fill the container they
  are in.
• Fluidity - There is very little attraction
  between gaseous particles, they flow past each
  other.
• Low Density - Most of a gas is empty space. The
  same amount of a gas as a liquid/solid takes up
  100 more space.

8

• Compressibility - because there is so much space
  between molecules in a gas they can be crowded
  closer together.
• Diffusion - spontaneous mixing of 2 substances
  due to random motion.
• A) Rate of Diffusion - depends upon
• 1) speed of molecules
• 2) size
• 3) attractive forces
• Effusion gas particles under pressure pass
  through a very small hole from one container to
  another.
• A) Rate of Effusion - is directly
  proportional to the velocity of the particles.

9
C. Characteristics of Gases

• Gases expand to fill any container.
• random motion, no attraction
• Gases are fluids (like liquids).
• no attraction
• Gases have very low densities.
• no volume lots of empty space

10
C. Characteristics of Gases

• Gases can be compressed.
• no volume lots of empty space
• Gases undergo diffusion effusion.
• random motion

11
10.2 Qualitative Description of Gases

• To describe gases accurately, you must use 4
  measureable quantities
• 1. Temperature
• 2. Pressure
• 3. Volume
• 4. Quantity or of Particles

12
Temperature Scales

• a) Celsius - developed by Anders
  Celsius(1701-1744)
• - 0oC freezing pt. of water
• - 37oC body temperature
• - 100oC boiling pt. of water
• - 20oC normal room temperature
• b) Fahrenheit - developed by inventor of
  Mercury thermometer - Gabriel Daniel Fahrenheit
  in 1714.
• - 32oF freezing pt. of water
• - 98.6oF body temperature
• - 212o F boiling pt. of water
• c) Kelvin - developed by William Thomson, Lord
  Kelvin.
• - K, Kelvin is the SI unit of Temperature
• - 0 K, Zero Kelvin - Absolute Zero
• - 273 K freezing pt. of water
• - 373 K boiling pt. of water

13
D. Temperature

• Always use absolute temperature (Kelvin) when
  working with gases.

14
E. Pressure
Which shoes create the most pressure?
15
E. Pressure

• Barometer
• measures atmospheric pressure

16
E. Pressure

• Manometer
• measures contained gas pressure

17
E. Pressure

• KEY UNITS AT SEA LEVEL
• 101.325 kPa (kilopascal)
• 1 atm 30 in. Hg
• 760 mm Hg
• 760 torr
• 14.7 psi

18
VOLUME

• Volume- amount of space an object takes up
• Solid L x W x H, cm3
• Fluid(Gas/Liquid)
• -- Graduated Cylinder in ml
• Quantity/ of Particles measured
• in moles(6.022 x 1023 particles)

19
F. STP
STP