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 in the reverse direction (from colder to hotter), work must be done on the system. This is the principle behind refrigeration and heat - pump systems. Thermal expansion is related to the change in size of a material with temperature, convection is a mode of heat transfer (but still follows the natural heat - flow direction without work input), and radiation is a form of heat transfer (again, following the natural heat - flow direction without work input in the context of this question).

Answer:

Work must be done on the system.