According to Avogadro's law, what can be said about gases?

Avogadro's law states that under the same conditions of temperature and pressure, equal volumes of different gases contain an equal number of molecules. This concept is foundational in understanding the behavior of gases and is critical in stoichiometric calculations involving gas reactions.

When a specific volume of gas is measured at a consistent temperature and pressure, it will always correspond to the same number of molecules, regardless of the type of gas being studied. This characteristic is crucial for predicting and calculating gas behaviors in both chemical reactions and in practical applications, such as estimating the volume of gas produced or consumed in a reaction.

The other statements do not accurately reflect Avogadro's law. For instance, the density of gases can vary significantly between different types; thus, not all gases have the same density. Similarly, gases can condense to form liquids under the right conditions, and while gases can have similarities in reactivity, they do not all react in the same way. Avogadro's law focuses specifically on volume and molecule count, which is why the statement that equal volumes of gases at the same temperature and pressure will contain the same number of molecules is the correct interpretation.