When ice is converted into water at 0${ }^{\circ }C$, it absorbs all the heat energy without an increase in its temperature. What is this heat energy known as?

Phase change is the process that occurs when ice turns into water. When a material changes phases, the process takes place at a specific constant temperature and requires a certain quantity of heat energy.
Think about a certain amount of water at room temperature. We are aware that if we raise the temperature of the environment or heat the water, the water will absorb some heat and raise in temperature.
Heat will be absorbed by the water until it reaches the same temperature as its surroundings. Further raising the temperature will eventually cause the water to begin to boil. We also see that the temperature of the water doesn't change when it starts to boil.
Actually, when water boils, it is turning into gas. i.e., its phase is shifting. At a constant temperature, phase change takes happen. Phase change does, however, need a certain quantity of heat energy.
Latent heat is the term for the needed heat.
Similar phase change occurs when ice turns into water. Additionally, this procedure occurs at a fixed temperature of 0°C. Latent heat is the name for the heat that must be provided for the phase change.

Hence, the correct answer is option B.