Difference Between Gas and Vapor

Main difference

People find it difficult to tell the difference between gas and vapor since the latter is also a type of gas and is not labeled as any other separate state of matter. Gas is the state of matter that has the least intermolecular attraction between its molecules and is invisible to the naked eye. Contrary to this, steam is the state of equilibrium between gases and liquid, which can return to its original, liquid form after pressure is exerted on it and the temperature is kept constant. Here it should be noted that the gaseous material that we get from liquids in the equilibrium state is known as steam. The gaseous material we get from water (liquid) is known as water vapor, not water gas.

Comparison chart

Gas Steam
State of matter One of the four states of matter. It is a gaseous state where the molecules are in the equilibrium state between gas and liquid.
Room temperature It’s still gas. The vapor returns to its original state, either liquid or solid.
Phase change The change in temperature and pressure is necessary to change the phase. A pressure change is required to return the vapor to its original state.
Visibility Not visible usually visible

What is gas?

Gas is classified as one of four states of matter; they have the distinctive feature of occupying the available space regardless of shape and volume. This characteristic is due to the presence of very little intermolecular attraction between the molecules. The other three states of matter are solid, liquid, and plasma. Solids have a fixed shape and volume, while liquids have a fixed volume but lack the feature of a fixed shape; they take the shape of the container into which they are poured. Gas molecules constantly move independently due to the weak attractive force between the molecules. The gas can fill any size container since the gas molecules are in constant motion. Compounds that even remain in the gaseous state are classified as gas. For example, carbon dioxide is classified as a gas, this is because it remains a gas even at room temperature, or in other words, we can say that CO2 never changes its state of matter. Therefore, you will never hear the term carbon dioxide vapor; it is always known as carbon dioxide gas.

What is steam?

Steam is a kind of gas that is in the equilibrium state between gas and water; it can return to its original liquid state if pressure is applied and the temperature is kept constant. The original state of steam can also be solid, so steam in its neutral phase at room temperature must be either liquid or solid. Vapors are more easily compressible compared to gases as they are constantly in transition. When the steam has to return to its original state, pressure is required on it and the temperature change is not required. Vapor is the term used for the gaseous molecule that can be the liquid at room temperature. Water evaporated from water is described as water vapor, and when pressure is exerted by water vapor, it returns to the liquid state. In other words, water vapor is water present in a gaseous state. The vapors are visible to the naked eye as the physical change in them occurs.

Gas vs. Vapor

  • Gas is one of the four states of matter, while vapor is a gaseous state in which it is in the equilibrium state between gas and liquid.
  • The gas would not change its state at room temperature or in the neutral state. Contrary to this, at room temperature, the vapor returns to its original state which is liquid or solid.
  • The change in temperature and pressure is necessary to change the phase of the gas. On the other hand, a pressure change is required to return the steam to the original state.
  • The gas cannot be seen with the naked eye, while the vapors are visible to the naked eye as they are in constant transition.

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