Which of the following phenomena cannot be explained by the molecular theory of matter?

Analysis of the Question

The question asks us to identify which of the listed heat transfer processes cannot be explained by the molecular theory of matter. The molecular theory of matter states that matter is made up of tiny particles (atoms or molecules) that are in constant motion and interact with one another.

Concept Explanation

To solve this, let's look at how heat is transferred in each process:

1. Conduction: Heat is transferred through a material by the vibration and collision of neighboring molecules. This is a direct application of the molecular theory.
2. Convection: Heat is transferred by the actual movement of fluid (liquid or gas) particles from one place to another. This movement is a result of changes in density caused by molecular kinetic energy. This is also explained by the molecular theory.
3. Expansion: When a substance is heated, its molecules gain kinetic energy and vibrate more vigorously, pushing each other further apart. This increase in average separation explains why substances expand.
4. Radiation: This is the transfer of heat in the form of electromagnetic waves (specifically infrared radiation). Unlike conduction and convection, radiation does not require a material medium to travel. It can occur in a vacuum (like heat from the sun reaching the Earth). Because it does not rely on the interaction or movement of matter particles, it is not explained by the molecular theory of matter.

Step-by-Step Solution

• Step 1: Evaluate Conduction. It requires a medium (atoms/molecules) to transfer energy. (Explained by molecular theory).
• Step 2: Evaluate Convection. It requires a medium (fluid) to transfer energy. (Explained by molecular theory).
• Step 3: Evaluate Expansion. It is a direct result of increased molecular vibration and separation. (Explained by molecular theory).
• Step 4: Evaluate Radiation. It involves electromagnetic waves that travel through space without needing particles. Therefore, the molecular theory is insufficient to explain how radiation propagates through a vacuum.

Conclusion

The phenomenon that cannot be explained by the molecular theory of matter is Radiation.

Exam Tip

Whenever you see a question about heat transfer, remember this: Conduction and Convection need "stuff" (matter) to happen, while Radiation is the "loner" that can travel through empty space (a vacuum).