09 First Law of Thermodynamics Notes

ÝÃ on the system . increase in internal energy, the heat supplied to the system and the w ork done (d) recall and use the first law of therm odynam ics expressed in term s of the (c) relate a rise in tem perature of a body to an increase in its internal energy . kinetic and potential energies associated w ith the m olecules of a system . system and that it can be expressed as the sum of a random distribution of (b) show an understandiń g that internal energy is determ ined by the state of the (a) define and use the concepts of specific heat capacity and specific latent heat. C andidates should be able to Learnintcomes F i rst L a w of Th e r mo d y na m i cs content n T herm odynam ics chapterlF irst L aw of Y E A R 5 - 6 P H Y S ©¥C S D E P A R T M E N T R A F F L E S ©¥N S T IT U T ©¥O N

H eat C apacity the electrical energy supplied . of S pecif©¥c involve he ating a m aterial throug h a change in tem pe rature A T and com pa ring it to D eterm ination T he m ain principles of determ ining specific heat ca pacity by electrical m ethods S . I. u n it : joule per kilogram per kelvin (J kg ' ' K - ' ) T = c h a n g e in te m p e ra tu re m - m a ss o f b o d y Q = q u a n tity o f h e a t W here c - sp e cific h e a t ca p a city c = Q mV e Y M athem atically, this definition can be expressed as capacity H eat heat required to raise the tem perature of unit m ass of the substance by one degree. specific T he tlum erjcä ©¥] iáfLiêl of the specific heat capacity of a substance is the quantity of capacity, it is im portant to m ake reference to the num eń ca©¥ va©¥ue. T he unit of heat capacity is not the joule and this is why, in the definition of heat S . I. u n it : joule per kelvin ( J K ' ' ) T = c h a n g e in te m p e ra tu re Q - q u a n tity o f h e a t W here C - h e a t ca p a city M athem atica©¥ly, this definition can be exp o ssed a s to raise the tem perature of the body by one degree . H eat T hq num erlca©¥ value* of the heat capacity of a body ia the quantity of heat required 9 . 1 Em ific H eat c ar¨¡Bw d S ©¥fic L atent H eat to the m echanlco of atom ©¥ and m o©¥ecules In a substance heat and m echan©¥ca©¥ w ork to the m icroscop©¥c concept of tem pera©¥ure , w hich relates internal energy l©¥ introduced to m ake U ©¥e link betw een the m acroscoprc conce￠«©¥ of system by m eans of both heat lran©¥fer and m echanrca©¥ w ork T he concept of conservation of energy u©¥ed in m echanics as it considers energy exchange to 1 processes w hich invo©¥ve heat and m echanical w ork . T hla ©¥aw ©¥©¥ an exlenrlon of M e T he nm t law of ©¥herm odynam ics ©¥©¥ uoiïlral ©¥o under©¥©¥anding therm od ynrm lc change the phase of a ©¥ubalance (e . g . B om B olid to liquid, o r from liquid to g©¥©¥) . ©¥nterac©¥ions. S ©¥m ilar©¥y, latent heal l©¥ u©¥od to ca©¥cula©¥e the energy required to and apecific heat capac©¥©¥y allow lor the calculation of ©¥em perature change©¥ In sucH tem perature cha