‘Gas’ vs ‘Vapor’
In physics, chemistry, and engineering, there are four states of matter, namely; solid, liquid, gas, and plasma. A solid matter has a fixed volume and shape. Matter in its liquid form has a fixed volume but adapts the shape of its container.
‘Gas’ is a state of matter where it expands to occupy any available volume. Molecules of gases are separated and have little effect on their motion. They move independently and can interact only through random collisions with each other.
‘Plasma’ is a state wherein gases are highly ionized at high temperatures. It has properties that are distinct from a gas which is why, although it is formed as a gas, it is considered the fourth state of matter.
‘Vapor’ is not a state of matter but is rather a substance in its gas phase at a temperature that is lower than its critical point. With a constant temperature and an increased pressure, a vapor can be turned back into liquid or solid.
A vapor is the result of boiling and evaporation. It is responsible for cloud formation, the process of distillation, and the extraction of a liquid sample for gas chromatography.
When heat is added to a solid substance, it melts into a liquid at its melting point and turns into a gas at its boiling point. Gas particles are vastly separated which makes gases invisible to the human eye.
Gases are described through their physical properties, namely; pressure, volume, number of particles, and temperature. They have low density and concentration. Vapors, on the other hand, are measured by the pressure of the gas.
Gases can exist in single states such that they have their own chemical and physical properties. When observed under a microscope, gases do not have definite shapes but appear as a collection of atoms, electrons, ions, and molecules while a vapor has a definite shape.
The physical properties of a gas and a vapor depend on the temperature and pressure of the gas that is formed. When water is boiled at a certain temperature and pressure, a vapor is formed. Fog and mist are actually atmospheric water vapor that has condensed into water droplets.
At room temperature, gases remain in their natural state, that is, they remain as gases. A vapor, in its natural state, can be a solid or liquid at room temperature. For example, steam is a water vapor that turns into water at room temperature. Oxygen, which is a gas, will still be a gas at room temperature.
Despite their differences, ‘gas’ and ‘vapor’ are oftentimes used interchangeably. This is true because a vapor is, in fact, a substance in its gas phase.
Summary:
1. ‘Gas’ is a state of matter while ‘vapor’ is not; it is a substance in its gas phase.
2. A gas is a substance that has not undergone a phase change while a vapor is a substance that has undergone a phase change.
3. At room temperature, a vapor can turn into a solid or liquid while a gas cannot.
4. Gases do not have definite shapes while vapors do.