Which is not a method by which heat may be transferred from a warmer substance to a colder substance?

• A. Conduction
• B. Retraction
• C. Convection
• D. Radiation

Answer: (B)

Heat moves from warmer to colder substances through three recognized mechanisms: conduction, convection, and radiation. Conduction happens when energy is transferred through direct contact or within a solid as molecules collide and pass energy along. Convection occurs in fluids (air or liquid) where warmer portions rise and cooler portions sink, creating a circulation that carries heat. Radiation transfers energy via electromagnetic waves and can occur without any medium, like the sun warming the earth or a radiant heater warming you from a distance. The term retraction does not describe any mechanism of heat transfer, so it doesn’t fit as a method of moving heat between substances.