Question

A substance has a freezing point of 24 °C. Which of the following is true for the substance?

a) When the substance is heated, its temperature will start rising above 24 °C after 50% of the liquid has changed to vapors.

b) When the substance is heated, its temperature will start rising above 24 °C after 100% of the solid has changed to liquid.

c) When the substance is cooled, its temperature will fall below 24 °C after 100% of the vapors have changed to liquid.

d) When the substance is cooled, its temperature will fall below 24 °C after 50% of the liquid has changed to solid.

Answer 1

The substance's temperature will stay at the freezing point until all the solid turns to liquid; only after will the temperature rise.

Step-by-step explanation:

The question is about the behavior of a substance at its freezing point. Option (b) 'When the substance is heated, its temperature will start rising above 24 °C after 100% of the solid has changed to liquid.' is the correct answer. This is because, at the freezing point or melting point, the substance can be in either the solid or liquid phase, and the temperature remains constant during this phase change. Hence, the temperature of a substance does not rise above its freezing or melting point until the entire amount of solid has changed into the liquid phase.