specific heat capacity

(noun)

The amount of heat that must be added (or removed) from a unit mass of a substance to change its temperature by one degree Celsius. It is an intensive property.

Examples of specific heat capacity in the following topics:

  • Specific Heat

    • The heat capacity is an extensive property that describes how much heat energy it takes to raise the temperature of a given system.
    • However, it would be pretty inconvenient to measure the heat capacity of every unit of matter.
    • This quantity is known as the specific heat capacity (or simply, the specific heat), which is the heat capacity per unit mass of a material .
    • Note that the total heat capacity C is simply the product of the specific heat capacity c and the mass of the substance m, i.e.,
    • Listed are the specific heats of various substances.

  • Specific Heat for an Ideal Gas at Constant Pressure and Volume

    • An ideal gas has different specific heat capacities under constant volume or constant pressure conditions.
    • Specific Heat for an Ideal Gas at Constant Pressure and Volume
    • The heat capacity at constant pressure of 1 J·K−1 ideal gas is:
    • The heat capacity ratio or adiabatic index is the ratio of the heat capacity at constant pressure to heat capacity at constant volume.
    • Potential energy stored in these internal degrees of freedom contributes to specific heat of the gas.

  • Calorimetry

    • Calorimetry requires that the material being heated have known thermal properties, i.e. specific heat capacities .
    • where δQ is the increment of heat gained by the sample, CV is the heat capacity at constant volume, cv is the specific heat at constant volume, and ΔT is the change in temperature.
    • Multiplying the temperature change by the mass and specific heat capacities of the substances gives a value for the energy given off or absorbed during the reaction:
    • It does not account for the heat loss through the container or the heat capacity of the thermometer and container itself.
    • where Cp is the specific heat at constant pressure, ΔH is the enthalpy of the solution, ΔT is the change in temperature, W is the mass of the solute, and M is the molecular mass of the solute.

  • Resistance and Resistivity

    • (A similar intrinsic/extrinsic relation exists between heat capacity C and the specific heat c).

  • Solving Problems with Calorimetry

    • The temperature change, along with the specific heat and mass of the solution, can then be used to calculate the amount of heat involved in either case.
    • Bomb calorimeters require calibration to determine the heat capacity of the calorimeter and ensure accurate results.
    • The temperature change produced by the known reaction is used to determine the heat capacity of the calorimeter.
    • Use these data to determine the specific heat of the metal.
    • Our experimental specific heat is closest to the value for copper (0.39 J/g °C), so we identify the metal as copper.

  • Heat Capacity

    • The heat capacity measures the amount of heat necessary to raise the temperature of an object or system by one degree Celsius.
    • In SI units, heat capacity is expressed in units of joules per kelvin (J/K).
    • The heat capacity of most systems is not a constant.
    • This defines the heat capacity at constant volume, CV.
    • Another useful quantity is the heat capacity at constant pressure, CP.

  • Thermal Pollution

    • As we learned in our Atom on "Heat Engines", all heat engines require heat transfer, achieved by providing (and maintaining) temperature difference between engine's heat source and heat sink.
    • Water, with its high heat capacity, works extremely well as a coolant.
    • But this means that cooling water should be constantly replenished to maintain its cooling capacity .
    • Some may assume that by cooling the heated water, we can possibly fix the issue of thermal pollution.
    • However, as we noted in our previous Atom on "Heat Pumps and Refrigerators", work required for the additional cooling leads to more heat exhaust into the environment.

  • Heat as Energy Transfer

    • Heat is the spontaneous transfer of energy due to a temperature difference.
    • This observation leads to the following definition of heat: Heat is the spontaneous transfer of energy due to a temperature difference .
    • Heat is often confused with temperature.
    • Heat is a form of energy, whereas temperature is not.
    • The calorie (cal) is a common unit of energy, defined as the energy needed to change the temperature of 1.00 g of water by 1.00ºC —specifically, between 14.5ºC and 15.5ºC, since there is a slight temperature dependence.

  • Latent Heat

    • Previously, we have discussed temperature change due to heat transfer.
    • where the latent heat of fusion, Lf, and latent heat of vaporization, Lv, are material constants that are determined experimentally.
    • Lf and Lv are collectively called latent heat coefficients.
    • Once all the ice has melted, the temperature of the liquid water rises, absorbing heat at a new constant rate of 1.00 cal/g⋅C (remember that specific heats are dependent on phase).
    • Heat from the air transfers to the ice causing it to melt.

  • Convection

    • We are given that ΔT is 10.0ºC, but we must still find values for the mass of air and its specific heat before we can calculate Q.
    • The specific heat of air is a weighted average of the specific heats of nitrogen and oxygen, which is c=cp≅1000 J/kg⋅C (note that the specific heat at constant pressure must be used for this process).
    • Instead heat diffusion in solids is called heat conduction, which we've just reviewed.
    • Heat is removed from the ocean when water evaporates.
    • If the water vapor condenses in liquid droplets as clouds form, heat is released in the atmosphere (this heat release is latent heat)  .