College of Massage Therapists of British Columbia (CMTBC) Practice Exam

What is the process called in which heated gas or liquid moves between two surfaces at different temperatures?

1. Conduction

2. Convection

3. Radiation

4. Evaporation

The correct answer is: Convection

The process referred to in the question is convection. Convection describes the transfer of heat through the movement of fluids (which can be liquids or gases) between areas of different temperatures. When a gas or liquid is heated, its particles gain energy, move more rapidly, and tend to rise, creating a current. The cooler areas, with denser particles, sink down, and this movement creates a cycle that transfers heat from one surface to another. In contrast, conduction involves the transfer of heat through direct contact between solid surfaces without the movement of the substance as a whole. Radiation refers to the transfer of heat through electromagnetic waves, which does not require a medium (like air or liquid) for heat transfer. Evaporation is the process by which liquid turns into vapor, associated with cooling, rather than active heat transfer between surfaces. Therefore, in the context of heated gas or liquid moving between two surfaces, convection is indeed the correct process described.