HEAT - HEAT CAPACITY

HEAT - HEAT CAPACITY
Heat capacity (or) Thermal capacity (C) :
    The amount of heat energy required to raise the temperature of a given mass of a substance through 1⁰C.
    Heat capacity = heat required to rise the temperature of the body through 1°C
    Mathematically, heat capacity =  .\(\frac{{{\text{amount of heat}}}}{{{\text{Rise in temperature}}}}\) \({\text{ = }}\,\,\frac{{\text{Q}}}{{\Delta {\text{t}}}} \Rightarrow H = \frac{Q}{{\Delta t}}\)

    Hence Thermal Capacity = mass × specific heat.
Units of heat capacity :
    S.I. unit of heat capacity  is J K^–1        
    CGS unit of heat capacity  is cal °C^–1
Water equivalent:
    -Mass of water which has same thermal capacity as that of  the substance is called water equivalent
    i) It is numerically equal to heat capacity (ms)
    ii) The S.I unit is kg
    iii) The C.G.S unit is g
Factors on which heat absorbed/given out by a body depends :
    i) directly proportional to the mass of the body. 
    ii) directly proportional to change in temperature of the body .
    iii) depends upon the nature of body.
         Q = m.C.\(\Delta t\)
Specific heat capacity or specific heat : 
    As Q = m.C.t. If m = 1 unit ; t = 1°C then Q = C, hence specific heat is the amount of heat required to raise the temperature of unit mass of the substance through 1°C or 1K.  Mathematically,    
      Specificheat = \(\frac{{{\text{quantity}}\;of\;{\text{heat}}}}{{{\text{mass of}}\;{\text{the}}\;{\text{substance}}\;{\text{ . change in temperature}}}}\)
        \(\Rightarrow \,\,C\,\, = \,\,\frac{Q}{{m.\,\,\Delta t}}\) 
Note :    
1.    Of all known substances water has the highest specific heat capacity. It can absorb a lot of heat without its temperature going up very much. It also cools down slower than other substances, as it has to lose more heat to cool down.
2.    The value of specific heat for a given substance is a constant quantity. However,the specific heat capacity for different substances is different.
Units of specific heat :
    S.I unit of specific heat = J kg^–1 K^–1
    CGS unit of specific heat is cal g^–1 °C^–1     
    Since 1cal = 4.18 J    
    therefore 1 cal g^–1 °C^–1  = 4180 J kg^–1 K^–1
 Advantages of high specific heat capacity of water :
    i)   Formation of wind cycles and weather. 
    A) Sea Breeze,         B) Land Breeze.
    ii)  Use of water in hot water bottles.
    iii) Use of water as coolant in car radiators.
    iv) Use of water in the internal heating of buildings.