The gaseous state is one of the four fundamental states of matter (along with the solid state, the liquid state and plasma). Substances that exist in the gaseous phase are commonly referred to as gases. The most common example of a gas is air (the air we breathe is a gas). It can also be considered as a mixture of many gases such as nitrogen, oxygen and carbon dioxide. Some examples of gases are listed below.
- Carbon Dioxide
- Carbon Monoxide
- Water Vapour
It can be noted that these substances exist in the gaseous phase under standard conditions for temperature and pressure (STP). However, if sufficient pressure is applied to the gas and if the gas is cooled to a low enough temperature, it can be liquefied.
What is a Gas?
Gases are substances that exist in the gaseous phase. The key characteristics associated with gases are:
- Gases do not have any defined volume. They expand to occupy the volume of the container they are placed in.
- Gases do not have any defined shape. They assume the shape of the container they are placed in.
- The intermolecular distances in the gaseous phase are relatively large. This means that the gas particles are placed at relatively large distances away from each other.
- The particles of the gas are in a constant state of random motion. They move around randomly and collide with each other and the walls of the container.
- Due to the collisions between the gas particles and the walls of the container, all gases are known to exert pressure on the walls of their containers.
Frequently Asked Questions on Examples of Gases
What is an Ideal Gas?
An ideal gas can be described as a gas in which all collisions between atoms or molecules are perfectly elastic in nature and the intermolecular attractive forces between the particles of the gas are not present. One can imagine the particles of an ideal gas as a series of colliding perfectly hard spheres but otherwise not interacting with each other. It is important to note that all ideal gases must obey the ideal gas law. This law equates the pressure exerted by a gas on the walls of its container, the absolute temperature of the gas, the volume occupied by the gas, the amount of gaseous substance (or the number of moles of gas), and the universal gas constant.
Which four physical properties are used to express the macroscopic properties of gases?
The four physical properties used to express the macroscopic properties of a gas are:
- The volume occupied by the gaseous substance
- The pressure exerted by the gaseous substance on the walls of its container
- The absolute temperature associated with the gaseous substance
- The number of gaseous particles
It is important to note that these four physical properties are related to each other for all gases. For ideal gases, this relationship is provided by the ideal gas law.
List some examples of homonuclear diatomic gases (at STP)
Examples of homonuclear diatomic compounds that exist in the gaseous phase under standard conditions for temperature and pressure are:
- Hydrogen gas (H2)
- Nitrogen gas (N2)
- Oxygen gas (O2)
- Chlorine gas (Cl2)
- Fluorine gas (F2)
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