Vapor vs Gas: Difference and Comparison

Vapor refers to the gaseous state of a substance that is a liquid or solid at room temperature and pressure, whereas gas denotes any substance in its gaseous state. While vaporization specifically involves the transformation from liquid to gas phase, gas can encompass a broader range of substances and states, including elements like oxygen and nitrogen in their gaseous form.

Key Takeaways

1. Vapor is a gaseous substance generated by the evaporation or boiling of a liquid, while gas is a state of matter that exists naturally in the atmosphere.
2. Vapor can be seen and felt as a mist or fog, while gas is invisible to the naked eye.
3. Vapor can be easily condensed back into a liquid state, while gas requires high pressure or low temperature to become a liquid.

Vapour vs Gas

The difference between vapour and gas is that vapour is not a gaseous state of matter, it can be solid or liquid, but gas is a gaseous state of matter. Although, they might seem confusing as both of them are in a gaseous state. 

Comparison Table

Feature	Vapor	Gas
Definition	Gaseous phase of a substance in equilibrium with its	Gaseous phase of a substance not necessarily in
	liquid or solid state	equilibrium with its liquid or solid state
Temperature Dependence	Typically exists below the critical temperature	Exists above the critical temperature and below
	of its substance	the critical pressure
Density	Higher density than gas at the same pressure	Lower density than vapor at the same pressure
Shape	No definite shape (conforms to container)	No definite shape (conforms to container)
Intermolecular Forces	Stronger intermolecular forces compared to gas	Weaker intermolecular forces compared to vapor
Examples	Water vapor, mercury vapor	Oxygen, nitrogen, carbon dioxide

What is Vapor?

Vapor is formed when a substance undergoes vaporization, a process where it transitions from its liquid or solid state to the gas phase. This transformation occurs when sufficient energy is added to overcome the intermolecular forces holding the substance in its condensed state.

Characteristics of Vapor:

1. State of Matter: Vapor exists in the gaseous state, sharing characteristics with gases. However, it differs in that it originates from substances with higher molecular weights that are liquids or solids under standard conditions.
2. Composition: The composition of vapor mirrors that of the substance from which it originates. For example, water vapor consists of water molecules, while vapor from volatile liquids contains molecules of the substance in the gas phase.
3. Temperature Dependence: The formation and behavior of vapor are heavily influenced by temperature. Higher temperatures increase the kinetic energy of molecules, facilitating vaporization and leading to increased vapor pressure.
4. Pressure and Volume Relationship: Similar to gases, vapor obeys the ideal gas law, demonstrating a proportional relationship between pressure and volume when temperature and the amount of substance remain constant.

Significance of Vapor:

1. Industrial Applications: Vapor plays a crucial role in various industrial processes, including distillation, evaporation, and vapor deposition. These processes are vital in sectors such as chemical engineering, pharmaceuticals, and semiconductor manufacturing.
2. Climate and Weather: Water vapor is a key component of Earth’s atmosphere and significantly influences weather patterns and climate. Understanding vapor’s behavior helps meteorologists predict weather phenomena such as precipitation, fog, and cloud formation.
3. Technological Advancements: Advances in vapor-related technologies have led to innovations in fields like energy production, where vapor turbines are used in power plants, and environmental science, with developments in vapor compression for refrigeration and air conditioning.

What is Gas?

Gas is a state of matter characterized by its ability to expand to fill the container it occupies, its low density compared to liquids and solids, and its tendency to diffuse rapidly. Unlike solids and liquids, gases have no definite shape or volume, and their particles move freely and independently of each other.

Characteristics of Gas

1. Particle Behavior: Gas particles exhibit constant, random motion, traveling in straight paths until they collide with other particles or the walls of their container. These collisions result in pressure, which is the force exerted by the gas per unit area.
2. Expansion and Contraction: Gases uniformly expand to fill the available space of their container. Conversely, when the volume of the container decreases, gases contract to occupy less space. This property allows gases to adapt to the shape and size of their container.
3. Compressibility: Gases are highly compressible, meaning their volume can be significantly reduced under pressure. When pressure is applied to a gas, the space between its particles decreases, leading to a decrease in volume.
4. Ideal Gas Behavior: The behavior of ideal gases is described by the ideal gas law, which relates pressure, volume, temperature, and the number of gas particles. While real gases may deviate from ideal behavior under certain conditions, the ideal gas law provides a useful approximation in many situations.

Significance of Gas

1. Industrial Applications: Gases are integral to various industrial processes, including combustion for energy production, chemical manufacturing, and as feedstocks for producing a wide range of products, such as fertilizers, plastics, and pharmaceuticals.
2. Environmental Impact: Understanding the composition and behavior of gases in Earth’s atmosphere is crucial for addressing environmental issues such as climate change, air pollution, and ozone depletion. Monitoring gas emissions and their effects on air quality and climate is essential for mitigating these challenges.
3. Technological Advancements: Gas-based technologies drive innovation in numerous fields, including transportation (e.g., internal combustion engines, fuel cells), healthcare (e.g., medical gases for anesthesia and respiratory therapy), and space exploration (e.g., propulsion systems for rockets).
4. Scientific Research: Gas behavior serves as the foundation for studying fundamental principles in physics and chemistry, such as thermodynamics, kinetics, and molecular interactions. Insights gained from gas studies contribute to advancements in scientific knowledge and technological development.

Main Differences Between Vapor and Gas 

• Origin:
  • Vapor originates from substances that are liquids or solids at room temperature and pressure, undergoing vaporization.
  • Gas refers to the general state of matter, encompassing substances in their gaseous phase, regardless of their origin.
• Formation:
  • Vapor forms when a substance undergoes vaporization, transitioning from liquid or solid to the gas phase.
  • Gas exists as a state of matter, either naturally occurring or artificially produced, without a specific transformation process like vaporization.
• Composition:
  • Vapor maintains the chemical composition of the substance from which it originates.
  • Gas can consist of various elements or compounds in their gaseous states, with diverse compositions and properties.
• Temperature Dependence:
  • Vaporization occurs at specific temperatures unique to each substance, influenced by factors such as pressure and molecular interactions.
  • Gas behavior is influenced by temperature changes but does not necessarily involve a phase transition like vaporization.
• Examples:
  • Examples of vapor include water vapor (steam), vaporized alcohol, or evaporated perfume.
  • Examples of gas include oxygen, nitrogen, carbon dioxide, and other substances in their gaseous states, whether naturally occurring or artificially produced.

References 

1. https://aip.scitation.org/doi/pdf/10.1063/1.1753975%40apl.2019.APLCLASS2019.issue-1
2. https://link.springer.com/article/10.1557/JMR.1986.0205