Gases and Kinetic Molecular Theory
States of Matter
Types of Matter:
Solid
Liquid
Gas
Matter Properties
States of Matter:
State
Closeness of Particles
Arrangement of Particles
Movement of Particles
Energy Level
Solid
Very close
Regular pattern
Vibrate around fixed position
Low energy
Liquid
Close
Randomly arranged
Move around each other
Greater energy
Gas
Far apart
Randomly arranged
Move quickly in all directions
Highest energy particles
Important Characteristics of Gases
Compressibility:
Highly compressible; decreased volume with external force, volume increases when the force is removed.
Thermal Expandability:
Volume increases when heated, decreases when cooled.
Viscosity:
Gases flow easier than liquids or solids.
Density:
Generally low; measured in grams per liter compared to grams per cubic centimeter for solids/liquids (1000x greater).
Miscibility:
Infinitely miscible; gases mix in any proportion (e.g., air).
Shape/Volume:
No definite shape or volume.
Key Gas Properties
Pressure (P):
Force applied per unit area.
Mathematically: ; measured in Pascal (N/m²) or Bar (1 bar = 10⁵ Pa = 100 kPa).
Standard Pressure:
Normal atmospheric pressure: .
Volume (V):
Three-dimensional space inside a container.
SI unit: cubic meter (m³); commonly liters (L).
Amount (n):
Measured in moles (n).
One mole = approximately particles.
Temperature (T):
Measured in Kelvin (K).
Conversion: (Absolute 0 = -273.15 °C).
Gas Laws
Boyle’s Law:
(volume inversely proportional to pressure, constant temperature and moles).
Charles' Law:
(volume directly proportional to temperature, constant pressure and moles).
Gay-Lussac's Law:
(pressure directly proportional to temperature, constant volume and moles).
Avogadro’s Law:
(volume directly proportional to moles, constant temperature and pressure).
Combined Gas Law
Combines Boyle's, Charles', and Gay-Lussac's laws:
.
Ideal gas represented by equation:
(where R = gas constant).
Kinetic Molecular Theory of Gases
Key Assumptions:
Gas molecules are in constant random motion.
Collisions with container walls create pressure.
Average velocity of gas molecules increases with temperature, resulting in increased collisions and pressure.
Key Concepts:
Pressure relates to molecular motion and energy transferred to walls of the container, defining temperature as a measure of average kinetic energy.
Average Kinetic Energy (KE):
and .
Density and Molar Mass of Gases
Derivation from ideal gas equation:
Density .
Molar mass .
Problems and Applications
Volume Calculation Problem:
Gases: 1 mole at STP = 22.4 L.
Sample Problems:
Determining volume at STP and calculating moles and mass from volume and pressure, using gas laws and principles.
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