Heat vs Energy

[MorganYun1H]

When talking about the definition of heat capacity, can heat and energy be used interchangeably? Is that why they both have the same units?

[Lena Nguyen 2H]

They are similar, but I don't think they can be used interchangeably. Heat is a specific type of energy, one that can be transferred by a temperature difference, which is why they have the same units. A change in energy can also come from work being done, but work is not heat. When using heat capacity, a sample may be heated, which causes an increase in internal energy, but the system may also do expansion work, so a change in energy and heat would not be the same.

[Austin Ho 1E]

Another way to remember Heat vs. Energy is thinking about rectangles and squares. All squares are rectangles, but not rectangles are squares: likewise, all heat is energy, but not all energy is heat. If you understand the context of the question they're asking, for instance if you're asked to find change in internal energy but there's no work done, we can understand that since delta U= q + w, if w=0, then delta U=q.