specific heat capacity

Examples of specific heat capacity in the following topics:

• Specific Heat and Heat Capacity

  • the specific heat capacity, often simply called specific heat, which is the heat capacity per unit mass of a pure substance.
  • Given the molar heat capacity or the specific heat for a pure substance, it is possible to calculate the amount of heat required to raise/lower that substance's temperature by a given amount.
  • In these equations, m is the substance's mass in grams (used when calculating with specific heat), and n is the number of moles of substance (used when calculating with molar heat capacity).
  • Specific heat capacity is the measure of the heat energy required to raise the temperature of a given quantity of a substance by one kelvin.
  • The above simulation demonstrates the specific heat and the latent heat.

• Water’s High Heat Capacity

  • The high heat capacity of water has many uses.
  • The water then remains hot for a long time due to its high heat capacity.
  • Water has the highest specific heat capacity of any liquid.
  • Specific heat is defined as the amount of heat one gram of a substance must absorb or lose to change its temperature by one degree Celsius.
  • In fact, the specific heat capacity of water is about five times more than that of sand.

• 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.

• Constant-Pressure Calorimetry

  • We already know our equation relating heat (q), specific heat capacity (C), and the change in observed temperature ($\Delta T$) :
  • We will now illustrate how to use this equation to calculate the specific heat capacity of a substance.
  • What is the specific heat of the unknown metal?
  • The specific heat capacity of the unknown metal is 0.166 $\frac {J} {g ^\circ C}$ .
  • The number of joules of heat released into each gram of the solution is calculated from the product of the rise in temperature and the specific heat capacity of water (assuming that the solution is dilute enough so that its specific heat capacity is the same as that of pure water's).

• Heating Curve for Water

  • A heating curve shows how the temperature changes as a substance is heated up at a constant rate.
  • A constant rate of heating is assumed, so that one can also think of the x-axis as the amount of time that goes by as a substance is heated.
  • The amount of heat added, q, can be computed by: $q=m\cdot C_{H_2O(s)}\cdot \Delta T$ , where m is the mass of the sample of water, C is the specific heat capacity of solid water, or ice, and $\Delta T$ is the change in temperature during the process.
  • Note that the specific heat capacity of liquid water is different than that of ice.
  • Note that the specific heat capacity of gaseous water is different than that of ice or liquid water.

• 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.

• Constant-Volume Calorimetry

  • The total heat given off in the reaction will be equal to the heat gained by the water and the calorimeter:
  • Keep in mind that the heat gained by the calorimeter is the sum of the heat gained by the water, as well as the calorimeter itself.
  • where Cwater denotes the specific heat capacity of the water ($1 \frac{cal}{g ^{\circ}C}$), and Ccal is the heat capacity of the calorimeter (typically in $\frac{cal}{^{\circ}C}$).
  • The sample is ignited by an iron wire ignition coil that glows when heated.
  • From the change in temperature, the heat of reaction can be calculated.

• 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.