Whether or not a substance is a gas depends on its temperature and pressure.

Example of gas molecules. At sea level the temperature is 20 C and at the higher altitude the temperature is -40 C. The water molecule is H 2 0. A gas mixture such as air contains a variety of pure gases.

The following list has substances known to be gases but with an unknown. In last unit we learn mole concept. Here are examples of common molecules.

Calculate their average speed v_rm avg root mean square speed v_rm rms and most probable speed v_rm mp. There are two kinds of diatomic gases such as Nitrogen N 2 Oxygen O 2 Hydrogen H 2 etc. Think about a helium balloon.

Heavy molecules effuse through a porous material more slowly than light molecules as illustrated schematically in Figure 68. A pure gas may be made up of individual atoms eg. A large helium-filled balloon is being used to lift scientific equipment to a higher altitude.

The lighter gas H 2 passes through the opening faster than O 2 so just after the stopcock is opened more H 2 molecules move to the O 2 side than O 2 molecules move to the H 2 side. In simple terms a molecule is an atom that forms a chemical bond with another atom. What causes diffusion of gases.

Examples of Gases Hydrogen Nitrogen Oxygen Carbon Dioxide Carbon Monoxide Water Vapour Helium Neon Argon Ozone. The speeds of eight molecules were found to be 10 40 40 60 60 60 80 and 100 ms. Oxygen or compound molecules made from a variety of atoms eg.