Understanding Heat Transfer Modes

Heat transfer is the movement of thermal energy from a hotter region to a cooler region. There are three primary modes:

• Conduction: Heat transfer through direct contact, involving molecular vibrations. No large-scale movement of matter occurs.
• Radiation: Heat transfer through electromagnetic waves. It does not require a medium.
• Convection: Heat transfer involving the bulk movement of fluids (liquids or gases). This motion carries thermal energy.

Analyzing the Question

The question specifically asks for the mode of heat transfer characterized by the actual motion of matter. Let's examine the options based on this definition:

• Conduction involves molecular vibrations but not the bulk movement of the material itself.
• Radiation transfers energy via waves, independent of matter movement.
• Vaporisation is a change of state (liquid to gas), not a primary mode of heat transfer like conduction, convection, or radiation.
• Convection inherently involves the movement of heated fluid parcels (matter) from one place to another, thus transferring heat.

Identifying the Correct Mode

Based on the definition, convection is the process where heat is transferred by the actual physical movement of the medium (like air or water currents). This directly matches the question's description.

Therefore, the correct mode of heat transfer by the actual motion of matter is Convection.