Gas is a type of matter that has no defined shape or volume. Gases can be made up of a single element, such as hydrogen gas (H2), a compound, such as carbon dioxide (CO2), or a mixture of several gases, such as air.
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.
Table of Content
List of 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.
- Hydrogen
- Nitrogen
- Oxygen
- Carbon Dioxide
- Carbon Monoxide
- Water Vapour
- Helium
- Neon
- Argon
- Ozone
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 – FAQs
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)
Differentiate between Real gas and Ideal gas.
Real gas obeys the laws of gas under certain conditions, whereas ideal gas always obeys the laws of gas. The two gases also differ in terms of the volume of their molecules, how they interact, and so on.
Ideal Gas is a hypothetical gas, which means that it does not exist in reality. It obeys the gas laws under all pressure and temperature conditions. Because there is no interparticle interaction in an ideal gas, it contains many minute particles that move randomly in all directions.
Real gas, on the other hand, is present in our surroundings. Only at high temperatures and low pressures do real gases obey gas laws. Since the molecules of these gases interact with one another, they do not behave like an ideal gas.
What do you understand by Monatomic, Diatomic, and Other Forms of gases?
Monatomic gases are made up of single atoms. These gases are formed from noble gases like helium, neon, krypton, argon, and radon. Other elements, such as oxygen, nitrogen, and hydrogen, typically form diatomic gases. Triatomic gases, such as ozone, are formed by a few pure elements (O3). Many common gases, such as carbon dioxide, carbon monoxide, nitrous oxide, propane, and freon, are compounds.
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