In conduction, heat transfer continues until what condition is met?

In conduction, heat transfer continues until what condition is met?

• A. Temperatures and speeds of molecular movement become equal
• B. Temperatures become equal but molecular movement does not
• C. Heat transfer stops when the temperature difference is zero
• D. Molecular movement speeds become equal while temperatures differ

Answer: (A)

Conduction ends when thermal equilibrium is reached—the temperatures on both sides are equal, so there is no longer a temperature gradient to drive heat flow. Temperature reflects the average kinetic energy of molecules, so when temperatures are equal, the average speeds of molecular movement also become the same. In other words, both the thermal energy and the average molecular motion have equalized. If temperatures are equal but speeds differ, that would contradict how temperature relates to kinetic energy, and if speeds are equal while temperatures differ, that also doesn’t align with that relationship. Therefore, the best description is that temperatures and average molecular speeds become equal.

Conduction ends when thermal equilibrium is reached—the temperatures on both sides are equal, so there is no longer a temperature gradient to drive heat flow. Temperature reflects the average kinetic energy of molecules, so when temperatures are equal, the average speeds of molecular movement also become the same. In other words, both the thermal energy and the average molecular motion have equalized. If temperatures are equal but speeds differ, that would contradict how temperature relates to kinetic energy, and if speeds are equal while temperatures differ, that also doesn’t align with that relationship. Therefore, the best description is that temperatures and average molecular speeds become equal.