Heat moves from to places. a. hot; hotter b. colder; cold c. colder; hotter d. hotter; colder

D. Heat moves spontaneously only from cold objects to hotter ones.

The entropy of a system measures its orderlessness. The greater the number of ways of energy distribution in a system, the greater its entropy. Temperature measures the average kinetic energy of particles within an object. Allowing two object of different temperature to come into contact and undergo heat exchange would thus induce a redistribution of energy between the two objects. Moving the "heat" from the colder object to the hotter one would force the energy into a smaller space than moving "heat" in the opposite direction would. As a result, the sum of entropy of the two objects would decrease if the colder object experience a decrease in temperature while the hotter one an increase in temperature, whereas cooling the hotter object while heating the colder object would increase lead to an increase in the entropy.

By the second law of thermodynamics, isolated systems with no heat exchange with their surroundings experience only spontaneous decrease but not increase in their entropy. As a result, only the transfer of heat from hotter objects to colder ones can be spontaneous.