What characteristic distinguishes volatile substances from non-volatile substances?

The characteristic that distinguishes volatile substances from non-volatile substances is primarily their evaporation rate. Volatile substances are those that have a high tendency to evaporate at room temperature due to their relatively low boiling points. This means they can easily transition from a liquid to a vapor state, making them more likely to be found as gases at ambient temperatures.

In contrast, non-volatile substances have much lower evaporation rates because they typically have higher boiling points, thus requiring more energy to convert them from liquid to gas. While boiling point can also be a distinguishing factor, the key aspect that actively illustrates the behavior of these substances in practical applications—like their presence in the air versus remaining in a liquid form—is the rate at which they evaporate.

Density and color do not effectively distinguish between volatile and non-volatile substances, as they may vary widely within both categories. Thus, focusing on the evaporation rate provides a clear and functional understanding of what makes a substance volatile.