Gases
1. Basic Properties of Gases
A gas is a state of matter in which particles move freely and occupy the
entire volume of their container.
Key Properties
Gases have several important characteristics:
1. No fixed shape or volume – gases expand to fill any container.
2. Highly compressible – large spaces exist between particles.
3. Low density compared to solids and liquids.
4. Diffuse easily – gas particles spread out and mix rapidly.
5. Exert pressure on the walls of their container.
Example
If perfume is sprayed in a room, the smell spreads because gas molecules
move randomly and diffuse through air.
2. Kinetic Theory of Gases
The Kinetic Molecular Theory (KMT) explains the behaviour of gases.
Main Assumptions
1. Gas particles are very small compared to the distance between
them.
2. Gas particles move in constant random motion.
3. Collisions between particles and container walls are elastic (no
energy lost).
4. There are no attractive or repulsive forces between particles (ideal
assumption).
5. The average kinetic energy of particles is proportional to
temperature (Kelvin).
Key Idea
Higher temperature → particles move faster → more energetic collisions.
3. Boyle’s Law
, Definition
Boyle’s Law states that:
For a fixed amount of gas at constant temperature, pressure is inversely
proportional to volume.
Equation
1
𝑃∝ OR 𝑃1 𝑉1 = 𝑃2 𝑉2
𝑉
Where:
• (P) = pressure
• (V) = volume
Explanation using Kinetic Theory
When volume decreases:
• Gas particles have less space
• Collisions with container walls increase
• Pressure increases
Example
If a gas at 1.0 atm occupies 4.0 L and is compressed to 2.0 L, the
pressure becomes:
𝑃1 𝑉1
𝑃2 =
𝑉2
(1.0)(4.0)
𝑃2 = = 2.0 𝑎𝑡𝑚
2.0
Pressure doubles.
4. Charles’ Law
Definition
Charles’ Law states:
For a fixed amount of gas at constant pressure, volume is directly
proportional to absolute temperature.
Equation
1. Basic Properties of Gases
A gas is a state of matter in which particles move freely and occupy the
entire volume of their container.
Key Properties
Gases have several important characteristics:
1. No fixed shape or volume – gases expand to fill any container.
2. Highly compressible – large spaces exist between particles.
3. Low density compared to solids and liquids.
4. Diffuse easily – gas particles spread out and mix rapidly.
5. Exert pressure on the walls of their container.
Example
If perfume is sprayed in a room, the smell spreads because gas molecules
move randomly and diffuse through air.
2. Kinetic Theory of Gases
The Kinetic Molecular Theory (KMT) explains the behaviour of gases.
Main Assumptions
1. Gas particles are very small compared to the distance between
them.
2. Gas particles move in constant random motion.
3. Collisions between particles and container walls are elastic (no
energy lost).
4. There are no attractive or repulsive forces between particles (ideal
assumption).
5. The average kinetic energy of particles is proportional to
temperature (Kelvin).
Key Idea
Higher temperature → particles move faster → more energetic collisions.
3. Boyle’s Law
, Definition
Boyle’s Law states that:
For a fixed amount of gas at constant temperature, pressure is inversely
proportional to volume.
Equation
1
𝑃∝ OR 𝑃1 𝑉1 = 𝑃2 𝑉2
𝑉
Where:
• (P) = pressure
• (V) = volume
Explanation using Kinetic Theory
When volume decreases:
• Gas particles have less space
• Collisions with container walls increase
• Pressure increases
Example
If a gas at 1.0 atm occupies 4.0 L and is compressed to 2.0 L, the
pressure becomes:
𝑃1 𝑉1
𝑃2 =
𝑉2
(1.0)(4.0)
𝑃2 = = 2.0 𝑎𝑡𝑚
2.0
Pressure doubles.
4. Charles’ Law
Definition
Charles’ Law states:
For a fixed amount of gas at constant pressure, volume is directly
proportional to absolute temperature.
Equation
