What is defined as the energy needed to change the state of one kilogram of a substance without a change in temperature?

The correct answer is Specific latent heat.

Comparison lens: State both sides of the comparison so the contrast is explicit rather than implied. This question asks: What is defined as the energy needed to change the state of one kilogram of a substance without a change in temperature. The correct response is Specific latent heat, because specific latent heat concerns energy transferred during a state change with no temperature rise. In Changes of state and specific latent heat, the marking point should connect directly to define specific latent heat as the energy needed to change the state of one kilogram of a substance with no change in temperature. 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 365 is distinct because it uses this exact question context and the comparison lens rather than a generic particle-model sentence.