Examples of Gases – What Is a Gas?

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Examples of Gases
A gas is a state of matter with no fixed volume or shape. Examples of gases include air, water vapor, and helium.

A gas is a state of matter that has no fixed volume or shape. In other words, a gas takes the shape and volume of its container. Gases condense into liquids or ionize into plasma. The particles in a gas are more distant from each other than in liquids. Gas particles may be elements or compounds. A gas may be either a pure substance (e.g., oxygen, helium, carbon dioxide) or a mixture (e.g., air, natural gas).

Key Takeaways

  • A gas is a state of matter with no fixed shape or volume.
  • Gases can be elements, compounds, or mixtures.
  • At room temperature, only a handful of elements exist naturally as gases.
  • The behavior of gases is often approximated using the ideal gas law, but real gases deviate at high pressures or low temperatures.
  • Vapor refers to the gaseous form of a substance normally liquid or solid at room conditions.

Examples of Gases

Here are examples of gases:

  • Acetylene
  • Air
  • Argon
  • Carbon dioxide
  • Carbon monoxide
  • Helium
  • Natural gas
  • Neon
  • Nitrogen
  • Oxygen
  • Ozone
  • Propane
  • Water vapor

Elements That Are Gases at Room Temperature

Several elements are gases at room temperature and ordinary pressure. Hydrogen, nitrogen, oxygen, fluorine, and chlorine form homonuclear diatomic gases. Oxygen also forms the homonuclear triatomic gas, ozone. All of the noble gases (helium, neon, argon, krypton, xenon, radon) are monatomic gases, except for oganesson. Although oganesson (element 118) resides in the noble gas group, it’s likely a solid at room temperature.

  • Hydrogen (H2)
  • Helium (He)
  • Nitrogen (N2)
  • Oxygen (O2)
  • Ozone (O3)
  • Fluorine (F2)
  • Neon (Ne)
  • Chlorine (Br2)
  • Argon (Ar)
  • Krypton (Kr)
  • Xenon (Xe)
  • Radon (Rn)

Gas vs Vapor

The terms gas and vapor are sometimes used interchangeably, but they have different connotations:

  • A gas is a substance that exists in the gaseous state at room temperature and pressure.
  • A vapor is the gaseous form of a substance that is normally liquid or solid at room conditions.

For example, water vapor refers to the gaseous form of water, which is normally a liquid.

Phase Changes of Matter

Phase Changes Involving Gases

Gases change into plasma, liquids, and gases. Learn about the different transitions.

  • Condensation: gas → liquid
  • Deposition: gas → solid
  • Ionization: gas → plasma

Conversely, solids and liquids change into gases through sublimation and evaporation, respectively.

Difference Between Ideal Gas and Real Gas

Chemistry and physics make a distinction between ideal gases and real gases. An ideal gas behaves according to the kinetic-molecular theory of gases and behaves according to the ideal gas law. Essentially, this means particles of an ideal gas take up no volume, are not attracted to each other, and interact with perfectly elastic collisions. No real gas is ideal, but under ordinary temperatures and pressures, their behavior is close enough to ideal that you can use the ideal gas law to approximate their behavior. However, at low temperature or high pressure, real gases deviate too much from ideal behavior. This is because high pressure force gas molecules together and their particle size matters. At low temperatures, particles lack enough kinetic energy to behave ideally. They experience attraction to each other and don’t bounce off each other with perfectly elastic collisions.

FAQs

Q: Are all gases invisible?
A: Not always. Many gases like oxygen and nitrogen are colorless, but others, such as chlorine (yellow-green) or nitrogen dioxide (reddish-brown), are visible.

Q: Can gases become liquids?
A: Yes. Gases condense into liquids by cooling then or increasing their pressure.

Q: Why do gases fill a container?
A: Gas particles move freely and rapidly, spreading out to occupy the entire volume of the container.

Q: What is the lightest gas?
A: Hydrogen is the lightest gas, with the lowest molecular weight of all elements.

Q: Do all gases smell?
A: No. Some gases, like oxygen and nitrogen, are odorless. Others, like hydrogen sulfide or chlorine, have strong, distinctive odors.

References

  • Haynes, W. M., ed. (2016). CRC Handbook of Chemistry and Physics (96th ed.). Boca Raton, Florida: CRC Press/Taylor and Francis. ISBN 978-1482260960.
  • John, James (1984). Gas Dynamics. Allyn and Bacon. ISBN 978-0-205-08014-4.