What defines an aerosol?

• A. A solid particle in a solid medium
• B. Liquid particles suspended in liquid
• C. Ultramicroscopic particles in air or gas
• D. Electrical discharge in a gaseous medium

Answer: (C)

An aerosol is characterized by ultramicroscopic particles that are suspended in air or another gas. This definition highlights the nature of aerosols as a mixture, where tiny droplets or solid particles are dispersed within a gaseous medium, allowing them to remain suspended for extended periods. This behavior is crucial in various fields, such as medicine, environmental science, and various industrial applications, as aerosols can play significant roles in air quality, respiratory health, and the dispersal of substances.

In the context of the other options, they each describe different phenomena that do not align with the definition of an aerosol. For instance, solid particles in a solid medium refer to a completely different type of matter interaction, while liquid particles suspended in liquid describes an emulsion rather than an aerosol. Additionally, an electrical discharge in a gaseous medium refers to a plasma state, not the suspension of particles in a gas. Understanding these distinctions is essential for accurately classifying different types of materials and their behaviors in various environments.