Gas vs. Vapor

What's the Difference?

Gas and vapor are both forms of matter that exist in a gaseous state. However, there are some key differences between the two. Gas refers to a substance that is in its gaseous state at room temperature and atmospheric pressure, such as oxygen or nitrogen. On the other hand, vapor refers to the gaseous form of a substance that is typically a liquid or solid at room temperature and atmospheric pressure, such as water vapor or steam. While both gas and vapor can expand to fill their containers and have no definite shape or volume, vapor is formed when a substance evaporates or sublimates, whereas gas is typically obtained through the process of heating or pressurizing a substance.


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State of MatterGas is a state of matter that is neither solid nor liquid.Vapor is the gaseous state of a substance that is normally a solid or liquid at room temperature.
CompositionGases can be composed of individual atoms or molecules.Vapors are composed of molecules of the substance in its gaseous state.
FormationGases can be formed through various processes like evaporation, combustion, or chemical reactions.Vapors are formed when a substance evaporates or sublimates into the gaseous state.
VisibilityGases are generally invisible to the naked eye.Vapors can be visible or invisible, depending on the substance and conditions.
TemperatureGases can exist at a wide range of temperatures.Vapors are typically formed at or below the boiling point of the substance.
PressureGases exert pressure on their surroundings.Vapors can also exert pressure, but it is usually lower than that of gases.
ExamplesAir, oxygen, nitrogenWater vapor, steam
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Further Detail


Gas and vapor are two terms often used interchangeably, but they have distinct characteristics and properties. Understanding the differences between gas and vapor is crucial in various scientific fields, including chemistry and physics. In this article, we will explore the attributes of gas and vapor, highlighting their unique features and behaviors.

Definition and Composition

Gas is a state of matter that exists at room temperature and pressure. It consists of individual atoms or molecules that are not bound together. These particles move freely and randomly, colliding with each other and the walls of their container. Examples of gases include oxygen, nitrogen, and carbon dioxide.

Vapor, on the other hand, is the gaseous phase of a substance that is typically a liquid or solid at room temperature and pressure. It is formed when a substance evaporates or sublimates. Vapor particles are also individual atoms or molecules, but they are derived from the substance in question. For instance, water vapor is formed when liquid water evaporates.

Physical Properties

Gas and vapor have several physical properties that differentiate them. Firstly, gases are compressible, meaning their volume can be reduced under pressure. This property allows gases to occupy any available space, filling their container completely. On the other hand, vapor is also compressible, but to a lesser extent compared to gases.

Secondly, gases and vapors both have low densities compared to liquids and solids. This is due to the large spaces between their particles. These low densities make gases and vapors lighter than the substances they originate from, allowing them to rise in the atmosphere.

Thirdly, gases and vapors have different boiling points. Gases have boiling points below room temperature, while vapors have boiling points at or above room temperature. This distinction arises from the fact that gases are already in their gaseous state, while vapors are formed when a substance reaches its boiling point and transitions from a liquid or solid to a gas.

Lastly, gases and vapors have different states of matter at standard temperature and pressure (STP). Gases exist as gases at STP, while vapors exist as either liquids or solids at STP. For example, water vapor condenses into liquid water at STP.

Behavior and Interactions

Gas and vapor particles exhibit different behaviors and interactions due to their distinct properties. Gases, being composed of freely moving particles, diffuse rapidly and mix uniformly with other gases. This property is evident when a gas is released in a room, quickly spreading and filling the entire space.

Vapor particles, on the other hand, tend to be more localized and concentrated. They are often found near the surface of the substance from which they originated. For instance, water vapor is commonly present above a boiling pot of water, but its concentration decreases as you move further away from the source.

Additionally, gases and vapors have different condensation behaviors. Gases can condense into liquids or solids when their temperature decreases or pressure increases. This process is known as condensation. On the contrary, vapors can condense back into their liquid or solid form by cooling or reducing the pressure. This phenomenon is called vapor condensation.

Furthermore, gases and vapors have different phase diagrams. Phase diagrams illustrate the relationship between temperature, pressure, and the states of matter. Gases have a wider range of temperatures and pressures in which they exist, while vapors have a more limited range due to their connection to a specific substance.

Applications and Examples

The attributes of gas and vapor find applications in various fields. Gases are extensively used in industries such as manufacturing, energy production, and transportation. For instance, natural gas is a vital energy source, while nitrogen gas is used in food packaging to extend product shelf life.

Vapors also have significant applications, particularly in the field of medicine. Inhalation therapy utilizes vaporized medications to deliver drugs directly to the respiratory system. Additionally, vaporizers are commonly used to create vapors from essential oils for aromatherapy purposes.

Examples of gases include hydrogen gas, helium gas, and chlorine gas. These gases have distinct properties and applications. Hydrogen gas is highly flammable and is used as a fuel source in various industries. Helium gas is lighter than air and is commonly used to fill balloons. Chlorine gas is a powerful disinfectant and is employed in water treatment processes.

Examples of vapors include water vapor, alcohol vapor, and gasoline vapor. Water vapor is present in the Earth's atmosphere and plays a crucial role in weather patterns. Alcohol vapor is used in breathalyzer tests to determine blood alcohol concentration. Gasoline vapor is highly flammable and poses a fire hazard, making it important to handle gasoline safely.


In conclusion, gas and vapor are distinct states of matter with unique attributes. Gas consists of freely moving particles, while vapor is the gaseous phase of a substance that is typically a liquid or solid at room temperature and pressure. They differ in physical properties, behavior, and interactions. Understanding these differences is essential in various scientific and practical applications. Whether it is the use of gases in industries or the role of vapors in medicine, both gas and vapor play significant roles in our daily lives.

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