Question

in which situations is heat flow present? check all that apply.
a substance feels warm.
one substance does not have a temperature.
two substances have the same temperature.
one substance transfers some of its thermal energy to another substance.
two substances differ in temperature.

Explanation:

• Heat flow occurs when there is a transfer of thermal energy. A substance feeling warm doesn't necessarily mean heat flow is occurring (it could just be at a certain temperature).
• All substances have a temperature, so the option "One substance does not have a temperature" is incorrect.
• When two substances have the same temperature, there is no heat flow (thermal equilibrium).
• When one substance transfers some of its thermal energy to another substance, heat flow is present.
• When two substances differ in temperature, heat flows from the hotter to the colder substance.

Answer:

One substance transfers some of its thermal energy to another substance, Two substances differ in temperature.