Motion requires energy, The more energy matter has the higher temperature it will also have. Typically this energy is supplied by heat. Heat loss or gain by matter is equivalent energy loss or gain.
With the observation above understood we con now ask the following question: by how much will the temperature of an object increase or decrease by the gain or loss of heat energy? The answer is given by the specific heat of the object.
Specific heat capacity, commonly called specific heat, is the amount of heat required to change a mass of a substance by a certain temperature. It is usually measured by the number of Joules(energy) required to raise the temperature of a gram of material by one degree Kelvin (or Celsius).
Specific heat governs property of matter how much heat it will take to raise its temperature for a given value of mass. Significance of the property is to predict the change in temperature due to a finite heat transfer to or from the system.
Factor Affecting Specific Heat -
1. Temperature Dependency - For both real and ideal gases the specific heats are the function of temperature this is the consequence of internal energy of internal energy of the molecules consisting of three components, translation, rotation and vibration.
From this model we expect specific heats of triatomic species more than the diatomic species are greater than monatomic species. In general the more complex is a molecule the is specific heats followed by the diatomic and lastly monatomic.
How it Varies With Temperature ?
Triatomic also have greater temperature dependence than diatomic a consequence of greater number of of vibration and rotational modes are available to become activated to cause changes as temperature increases. In comparison the monatomic species have nearly constant specific heats over a wide range of temperatures in fact the Hydrogen(monatomic) atom's specific heat is constant, C= 20.786 kJ/kmol-K from 200K - 5000K.
2. Quantum Effect - Quantum effects require that whenever energy be stored in any mechanism associated with a bound system which confers a degree of freedom, it must be stored in certain minimal-sized deposits (quanta) of energy. In general, for this reason, specific heat capacities tend to fall at lower temperatures where the average thermal energy available to each particle degree of freedom is smaller(smaller quantum size). Due to this process, as temperature falls toward absolute zero, so also does heat capacity.
3. Phase - Liquid phase has greater irregularity comparing to solid state. This causes specific heats of liquid to be greater than solid followed by solid having smallest number of specific heat. For example, at 1 atmospheric pressure, ice ( -10C temperature) has specific heat 2.11Jule/gram-Kelvin, water at 25C has 4.183Jule/gram-Kelvin. When it comes to gaseous-Liquid comparison no such relation is followed due to irregularity offered by gas molecules to support to an uninterrupted energy transfer chain.
3.Atomic Bonds- Hydrogen-containing polar molecules like ehanol, ammonia and water have powerful, intermolecular hydrogen bonds when in their liquid phase. These bonds provide another place where heat may be stored as potential energy of vibration, even at comparatively low temperatures. Hydrogen bonds account for the fact that liquid water stores nearly the theoretical limit of 3 R per mole of atoms, even at relatively low temperatures (i.e. near the freezing point of water).
4. Metal Composition- In the case of alloys, there are several conditions in which small impurity concentrations can greatly affect the specific heat. Alloys may exhibit marked difference in behavior even in the case of small amounts of impurities being one element of the alloy; for example impurities in semi-conducting ferromagnetic alloys may lead to quite different specific heat properties.
5. Further more numerical value of specific heat also depends upon unit of description. Obviously species having higher moleculer weight will have higher specific heat with unit Jule/mol-Kelvin rather than Jule/gram-Kelvin. For convenience per mole basis specific heat is termed as molar specific heat .
Quick Fact - Water has an unusually high specific heat, and the human body is mostly water, meaning that humans can absorb or lose a lot of heat without drastic changes in internal temperature.
Specif heat of human body is around 3.5 Jule/gram-Kelvin or KiloJule/Kilogram-Kelvin
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