Interpret a heating graph that shows a substance being heated from solid to liquid. Identify the sections where temperature increases and where it remains constant.

In the heating graph, the temperature increases during the solid phase until it reaches the melting point, where it remains constant while the substance changes to liquid. After the change of state, the temperature continues to increase as the liquid is heated.

Boundary lens: Keep this separate from nearby specification points that use similar words but test a different idea. This question asks: Interpret a heating graph that shows a substance being heated from solid to liquid. Identify the sections where temperature increases and where it remains constant. The correct response is In the heating graph, the temperature increases during the solid phase until it reaches the melting point, where it remains constant while the substance changes to liquid. After the change of state, the temperature continues to increase as the liquid is heated., because changes of state are explained by particle energy and arrangement. In Changes of state and specific latent heat, the marking point should connect directly to interpret heating and cooling graphs that show temperature changes and flat sections during changes of state. 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 430 is distinct because it uses this exact question context and the boundary lens rather than a generic particle-model sentence.