Examples of heat capacity in the following topics:
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- the molar heat capacity, which is the heat capacity per mole of a pure substance.
- Molar heat capacity is often designated CP, to denote heat capacity under constant pressure conditions, as well as CV, to denote heat capacity under constant volume conditions.
- Units of molar heat capacity are $\frac{J}{K\bullet mol}$.
- the specific heat capacity, often simply called specific heat, which is the heat capacity per unit mass of a pure substance.
- Now we can plug our values into the formula that relates heat and heat capacity:
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- 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's high heat capacity is a property caused by hydrogen bonding among water molecules.
- Water has the highest specific heat capacity of any liquid.
- In fact, the specific heat capacity of water is about five times more than that of sand.
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- 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.
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- An ideal gas has different specific heat capacities under constant volume or constant pressure conditions.
- The heat capacity at constant volume of nR = 1 J·K−1 of any gas, including an ideal gas is:
- The heat capacity at constant pressure of 1 J·K−1 ideal gas is:
- Measuring the heat capacity at constant volume can be prohibitively difficult for liquids and solids.
- The heat capacity ratio or adiabatic index is the ratio of the heat capacity at constant pressure to heat capacity at constant volume.
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- 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 .
- The specific heat is the amount of heat necessary to change the temperature of 1.00 kg of mass by 1.00ºC.
- 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.,
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- Data collected during a constant-pressure calorimetry experiment can be used to calculate the heat capacity of an unknown substance.
- 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.
- 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).
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- The change in temperature of the measuring part of the calorimeter is converted into the amount of heat (since the previous calibration was used to establish its heat capacity).
- Knowledge of the heat capacity of the surroundings, and careful measurements of the masses of the system and surroundings and their temperatures before and after the process allows one to calculate the heat transferred as described in this section.
- The temperature increase is measured and, along with the known heat capacity of the calorimeter, is used to calculate the energy produced by the reaction.
- 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.
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- 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.
- In addition, the object placed inside the calorimeter shows that the objects transferred their heat to the calorimeter and into the liquid, and the heat absorbed by the calorimeter and the liquid is equal to the heat given off by the metals.
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- 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.
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- 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.