Question

1. according to the second law of thermodynamics, which is a requirement for thermal energy to flow from colder objects to hotter objects? (1 point)

thermal expansion must occur in the system.
work must be done on the system.
convection must occur within the system.
radiation must alter the system.

Explanation:

According to the second law of thermodynamics, heat naturally flows from hotter to colder objects. For heat to flow from colder to hotter, an external influence is needed. Work done on the system (like in a refrigerator) provides this external influence. Thermal expansion, convection, and radiation don't directly enable heat flow from cold to hot as required here.

Answer:

Work must be done on the system.