What term describes the amount of heat needed to raise the temperature of one kilogram of a substance by one Celsius degree?

The correct term for the amount of heat required to raise the temperature of one kilogram of a substance by one Celsius degree is specific heat. Specific heat is a physical property of materials that reflects their ability to absorb energy. It indicates how much energy (in joules) is needed to increase the temperature of a given mass of a substance by a certain amount.

In contrast, latent heat refers to the heat required for a phase change of a substance—such as melting or boiling—without changing its temperature. Thermal conductivity measures how well a material conducts heat, rather than the heat needed for a temperature change. Heat capacity, while related, is a broader term that refers to the amount of heat required to change the temperature of a substance irrespective of mass; specific heat is focused specifically on the temperature change per unit mass. Thus, specific heat is the most precise term to describe the situation presented in the question.