1i In any thermodynamic process between equilibrium state i and f, the quantity Q+W has the same value. this quantity is equal to the change in he internal energy int liv The first law of the thermodynamics is a general result that is thought to apply to every process in nature that proceeds between equilibrium states 象 Ecl aion of energy prin
(iii) In any thermodynamic process between equilibrium state i and f, the quantity Q+W has the same value. This quantity is equal to the change in the internal energy . (iv) The first law of the thermodynamics is a general result that is thought to apply to every process in nature that proceeds between equilibrium states. Eint
23-4 Heat capacity(热容) and specific heat(比热) 1. Heat capacity c Q (23-7) △T 2. Specific heat The heat capacity per unit mass of a body C O (23-8) mm△T The heat capacity C) is characteristic of a particular object but the specific heat (c) characterizes a kind of substance
23-4 Heat capacity (热容)and specific heat（比热） 1. Heat capacity C： (23-7) 2. Specific heat： The heat capacity per unit mass of a body (23-8) The heat capacity (C) is characteristic of a particular object, but the specific heat (c) characterizes a kind of substance. T Q C = m T Q m C c = =
Usually both C and c depend on the temperature and condition under which the heat Q is added to the material Q=「mc(m)T=m(m)(23-10 3. Molar heat capacity If we multiply the specific heat by the molar mass M, we obtain the“ molar heat capacit M n--- the molar number 0 m△TnAT
Usually both C and c depend on the temperature and condition under which the heat Q is added to the material. 3. Molar heat capacity If we multiply the specific heat by the molar mass M, we obtain the “molar heat capacity”. Q = mc(T)dT = m c(T)dT (23-10) n T Q m T Q cmol M = = n--- the molar number
TABLE 23-2 Heat Capacities of Some Substances limiting value Molar Heat Capacity Heat Capacity :oE 20 Substance (/kg. K) (J/mol·K) Elemental solids Lead 129 26.7 每10 Carbon Tungsten 24.8 Silver 236 25.5 Copper 387C 4.6 Carbon 502 602 3R 400 600 Aluminum 900 Temperature(K) Measured at room temperature and atmospheric pressure 4. Heats of transformation( atent heat(潜热 When heat enters a sample the sample may change from one phase or state to another. In this case, the temperature of the sample does not rise vice versa
*4. Heats of Transformation (Latent heat(潜热)) When heat enters a sample, the sample may change from one phase or state to another. In this case, the temperature of the sample does not rise. Vice versa. Larger 3R *Measured at room temperature and atmospheric pressure
Sample problem 23-3 A cube of copper of mass m=75 g is placed in an oven at a temperature of To=312 C until it comes to thermal equilibrium. the cube is then dropped quickly into an insulated beaker(M) containing a quantity of water of mass mw=220 g. the heat capacity of the beaker alone is Cb=190 J/K. Initially the water and the beaker are at a temperature of Ti =12.00c. what is the final equilibrium temperature Tf of the system consisting of the copper +water+beaker?
A cube of copper of mass mc=75 g is placed in an oven at a temperature of T0=3120C until it comes to thermal equilibrium. The cube is then dropped quickly into an insulated beaker(烧杯) containing a quantity of water of mass mw=220 g. The heat capacity of the beaker alone is Cb=190 J/K. Initially the water and the beaker are at a temperature of Ti=12.00c. What is the final equilibrium temperature Tf of the system consisting of the copper +water+beaker? Sample Problem 23-3