Understanding Heat Required to Change Temperature

The question asks for the scientific term that describes the amount of heat energy needed to increase the temperature of a specific amount (unit mass) of a material by a specific amount (one degree Centigrade).

Let's look at the definition of the terms provided in the options:

• Specific Heat: Specific heat capacity (often simply called specific heat) is defined as the quantity of heat required to raise the temperature of unit mass of a material by one degree Celsius (or Centigrade) or Kelvin. Its SI unit is joules per kilogram per Kelvin ($\text{J/kg} \cdot \text{K}$) or joules per kilogram per degree Celsius ($\text{J/kg} \cdot \text{^\circ C}$).
• Thermal Expansion: Thermal expansion is the tendency of matter to change its volume in response to changes in temperature. This is not a measure of heat required for a temperature change.
• Temperature Stress: Temperature stress is stress induced in a material when it is not allowed to expand or contract freely with changes in temperature. This is related to thermal expansion and mechanical properties, not heat required for a temperature change.
• Heat of Hydration: Heat of hydration is the heat evolved when a substance dissolves in water or combines chemically with water. This is a type of heat released during a chemical process, not the heat required to change the temperature of a material.

Comparing the definition given in the question with the definitions of the options, it is clear that the question describes Specific Heat.

The formula relating heat energy ($Q$), mass ($m$), specific heat capacity ($c$), and temperature change ($\Delta T$) is:

$$Q = mc\Delta T$$

From this formula, we can see that if $m=1$ (unit mass) and $\Delta T=1$ (one degree change), then $Q=c$. Therefore, the heat required is equal to the specific heat capacity.

Conclusion on Heat and Specific Heat

Based on the analysis of the definitions, the quantity of heat required to raise the temperature of unit mass of a material by one degree Centigrade is precisely the definition of specific heat.

Revision Table: Key Thermal Concepts

Additional Information on Specific Heat and Heat Capacity

While specific heat is defined per unit mass, the total heat capacity of an object is the total amount of heat required to raise the temperature of that specific object by one degree. Heat capacity ($C$) is related to specific heat ($c$) by the mass ($m$) of the object:

$$C = mc$$

Materials have different specific heat capacities. Water, for example, has a relatively high specific heat capacity ($\approx 4186 \, \text{J/kg} \cdot \text{^\circ C}$), meaning it takes a lot of energy to change its temperature. Metals like iron have lower specific heat capacities, so they heat up and cool down more quickly with the same amount of heat energy.

Specific heat is an intrinsic property of a material, meaning it doesn't depend on the size or shape of the sample, only on the substance itself (and sometimes its phase and temperature).