How does heat flow according to the definitions?

How does heat flow according to the definitions?

• A. From hot to cold
• B. From cold to hot
• C. In all directions equally
• D. Only within solids

Answer: (A)

Heat is energy in transit due to a temperature difference, so it moves from where it is hotter to where it is cooler, along the temperature gradient. This directional flow is what the definition captures, and it can happen through conduction, convection, or radiation. The best statement reflects this natural tendency: heat goes from hot to cold. The other ideas don’t fit because transferring energy from cold to hot would require external work or a reversed gradient, heat doesn’t spread equally in all directions without a gradient, and heat transfer isn’t limited to solids—conduction, convection, and radiation can move heat through liquids, gases, and even across empty space.

Heat is energy in transit due to a temperature difference, so it moves from where it is hotter to where it is cooler, along the temperature gradient. This directional flow is what the definition captures, and it can happen through conduction, convection, or radiation. The best statement reflects this natural tendency: heat goes from hot to cold. The other ideas don’t fit because transferring energy from cold to hot would require external work or a reversed gradient, heat doesn’t spread equally in all directions without a gradient, and heat transfer isn’t limited to solids—conduction, convection, and radiation can move heat through liquids, gases, and even across empty space.