Gas Properties and Kinetic Molecular Theory

Properties Distinguishing Gases

• Gases expand to occupy any container and have no fixed volume.

Kinetic Molecular Theory (KMT)

• KMT explains gas behavior regarding temperature and pressure.

Basic Assumptions of Kinetic Theory

• Gas particles are considered to have no volume.
• Particles are in constant, random, straight-line motion.
• Collisions between particles are perfectly elastic.
• There are no attractive or repulsive forces between gas molecules.
• Average kinetic energy relates directly to temperature.

Real Gas Behavior

• Real gases possess volume and exhibit forces of attraction between particles, contradicting KMT assumptions.

Ideal Gas Conditions

• Near-ideal gas behavior occurs at high temperatures, low pressure, with non-polar molecules, and small particle sizes.

Compressibility of Gases

• Gas particles have large relative distances, resulting in considerable empty space and thus high compressibility.
• Compressibility measures the volume decrease of matter under pressure.

Gas Characteristics Variables

• Key variables defining gas characteristics include volume (L), temperature (K), amount of moles (n), and pressure (atm, kPa).

Gas Pressure Mechanism

• Gas pressure arises from particles colliding with the walls of their container.

Pressure Measurement Devices

• A barometer measures atmospheric pressure, while a manometer measures the pressure of a specific gas.

Effects of Temperature on Gas Behavior

• Increasing temperature raises the average kinetic energy of gas particles, leading to faster motion.
• Faster particles strike container walls more energetically, resulting in higher pressure.

Average Kinetic Energy Relation

• Average kinetic energy of gas particles directly correlates to their Kelvin temperature; as one increases, so does the other.

Standard Temperature and Pressure (STP)

• STP is defined as either 0 degrees Celsius and 1 atm or 273 K and 101.325 kPa.

Pressure Units

• The SI unit for pressure is kilopascals (kPa), while pounds per square inch (psi) is commonly used in the U.S.

Atmospheric Pressure Conversion Factors

• 760 torr = 1 atm
• 14.7 psi = 1 atm
• 760 mmHg = 1 atm
• 101.325 kPa = 1 atm

Temperature Conversion Factors

• To convert Fahrenheit (°F) to Celsius (°C): ºC = (5/9)(ºF - 32)
• To convert Celsius (°C) to Kelvin (K): K = °C + 273