specific heat

(noun)

the amount of heat necessary to raise one gram of a substance by one degree Celsius

Related Terms

  • isotherm
  • critical point

Examples of specific heat 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.
  • 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 of water is 4.18 $\frac {J} {g^\circ C}$)
    • The specific heat capacity of the unknown metal is 0.166 $\frac {J} {g ^\circ C}$ .
  • 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.
  • 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.
  • Variation of Physical Properties Within a Group

    • Metallic elements are shiny, usually gray or silver in color, and conductive of heat and electricity.
  • Solutions and Heats of Hydration

    • When ions dissolve in water, the stabilizing interactions that result release energy called the "heat of hydration."
    • Ionic solids are insoluble in the majority of non-aqueous solvents, but they tend to have high solubility specifically in water.
    • M^+ (g) + X^-(g) \to M^+ (aq) + X^-(aq)$ [heat of hydration]
    • A hot solution results when the heat of hydration is much greater than the lattice energy of the solute.
    • Predict whether a given ionic solid will dissolve in water given the lattice energy and heat of hydration
  • Heat and Work

    • Heat transfer by convection occurs through a medium.
    • Lastly, heat can also be transferred by radiation; a hot object can convey heat to anything in its surroundings via electromagnetic radiation.
    • Like heat, the unit measurement for work is joules (J).
    • Heat and work are related.
    • Work can be completely converted into heat, but the reverse is not true: heat energy cannot be wholly transformed into work energy.
  • The Three Laws of Thermodynamics

    • This law says that there are two kinds of processes, heat and work, that can lead to a change in the internal energy of a system.
    • Since both heat and work can be measured and quantified, this is the same as saying that any change in the energy of a system must result in a corresponding change in the energy of the surroundings outside the system.
    • If heat flows into a system or the surroundings do work on it, the internal energy increases and the sign of q and w are positive.
    • Conversely, heat flow out of the system or work done by the system (on the surroundings) will be at the expense of the internal energy, and q and w will therefore be negative.
    • Specifically, the entropy of a pure crystalline substance (perfect order) at absolute zero temperature is zero.
  • Changes in Energy

    • The concept of entropy can be described qualitatively as a measure of energy dispersal at a specific temperature.
    • This is because some energy is expended as heat, limiting the amount of work a system can do.
    • The state function has the important property that in any process where the system gives up energy ΔE, and its entropy falls by ΔS, a quantity at least TR ΔS of that energy must be given up to the system's surroundings as unusable heat (TR is the temperature of the system's external surroundings).
  • Historical Background

    • In an experiment designed to prepare ammonium cyanate from silver cyanate, he heated the latter with ammonium chloride expecting the outcome shown below.
    • Thus, strongly heating organic substances such as carbohydrates and proteins yielded water, ammonia and carbonaceous solids (all inorganic), with loss of the vial essence.
    • First, carbon disulfide, obtained by reaction of carbon with sulfur, was converted to carbon tetrachloride by heating with chlorine, and the simultaneous pyrolysis of CCl4 yielded a mixture of products which included tetrachloroethene, presumably formed from dichlorocarbene (:CCl2).
    • CS2 + Cl2 + heat —> CCl4 + Cl2C=CCl2 + many other products
    • That the atoms of allyltoluidine should, in the course of one reaction, selectively reorganize and combine in this specific fashion is beyond all reasonable probability.
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