Explain how heating a substance can change its internal energy without changing its temperature.

Heating a substance can change its internal energy by increasing the potential energy of the particles, especially during a phase change, while the temperature remains constant until the phase change is complete.

Exam lens: Write the relationship, substitute values only when needed, and finish by interpreting the result. This question asks: Explain how heating a substance can change its internal energy without changing its temperature. The correct response is Heating a substance can change its internal energy by increasing the potential energy of the particles, especially during a phase change, while the temperature remains constant until the phase change is complete., because internal energy combines particle kinetic and potential energy. In Internal energy, the marking point should connect directly to distinguish temperature from internal energy. If the question includes values, the working must keep the appropriate unit and operation; if it is an explanation, it must name the relevant particle behaviour or energy change. This item belongs to Internal energy and energy transfers, so avoid answers that switch to a different quantity, confuse heat with temperature, or describe gas pressure without collisions when collisions are the reason. Checkpoint 239 is distinct because it uses this exact question context and the exam lens rather than a generic particle-model sentence.