Common Gases:

* Oxygen (O2): Essential for respiration.

* Nitrogen (N2): The most abundant gas in the atmosphere.

* Carbon Dioxide (CO2): A greenhouse gas produced by respiration and combustion.

* Helium (He): A light, inert gas used in balloons and for cryogenics.

* Argon (Ar): An inert gas used in lighting and welding.

Other Gases:

* Methane (CH4): A natural gas found in underground deposits.

* Propane (C3H8): A fuel gas used for cooking and heating.

* Chlorine (Cl2): A toxic gas used in water purification.

* Ammonia (NH3): A pungent gas used in fertilizers and cleaning products.

* Hydrogen (H2): A flammable gas with potential for clean energy.

* Steam (H2O): Water in its gaseous state.

Key Characteristics of Gases:

* No fixed shape or volume: Gases take the shape and volume of their container.

* High compressibility: Gases can be easily compressed.

* Low density: Gases are less dense than liquids or solids.

* Rapid diffusion: Gases readily mix with each other.

* Constant random motion: Gas molecules move rapidly and randomly.

Let me know if you'd like more examples or details about specific gases!