HEAT Sumber Gambar : site: gurumuda.files.wordpress.com Sumber Gambar Fisika SMK Teknologi, Direektorat SMK

Heat Heat Definition “ the energy flowing from the hotter bodies to the colder bodies when they are in contact each other until their temperatures are identical and thermal equilibrium is reached“ Heat energy form The motion of atom, molecules & other particles which comprise a matter Related with page: 2 definition

Specific heat and heat capacity Heat capacity is the amount of heat required by an object to change its temperature of 1o C atau 1 K. Q = Heat ( Joule ) T = change of temperature (o C atau K ) C = heat capacity ( Jolue/ o C atau Jolue/ K) page: 3 head capacity

Specific heat and heat capacity The specific heat is the amount of heat (in calories) that is required to raise the computer of one gram of a substance one degree Celcius or one Kelvin c = specific heat ( Jolue/KgoC atau Jolue/Kg K) m = mass (Kg) page: 4 specific heat

Specific heat of several substances (at 20 ºC and 1 atm) (J/kg K) Molar specific heat (J/mol K) Gold 130 25,6 Lead 26,8 Mercury 140 28,0 Copper 385 24,4 Aluminum 900 24,3 Water 4190 75,4 page: 5 specific heat

Conservation energy law for heat Conservation energy law for heat complies the principle proposed by Joseph Black, so is called the Black’s principle. “when mix two substance, the amount of heat released by the higher temperature substance is equal with the amount of heat absorbed by the lower temperature substance ”. TA TB TA > TB T A releases the heat & B absorbs the heat Qreleased = Qabsorbed Both of final temperature (T) are same (equal) page: 6 Black’s principle

Change of phase Gas liquid solid Condensation freezing evaporating sublimation The change of phase of a substance is caused by the substance releasing heat The change of phase of a substance is caused by the substance absorbing heat page: 7 change of phase

Melting latent heat (melting heat) boiling latent heat (boiling heat) Latent heat (L) Latent is the amount of heat that required to change 1 kg phase of substance at a constant temperature Melting latent heat (melting heat) Freezing latent heat (freezing heat) = latent heat(L) Q = heat (J) m = substance mass zat (Kg) boiling latent heat (boiling heat) condensation latent heat (condensation heat) = page: 8 latent heat

Factors influencing the change of phase P increase Its boiling point increases Pressure (P) Factors influencing the change of phase Its boiling point increase Impurity of substance page: 9 change of phase

Heat transfer Heat tends to move from higher temperature to lower temperature region solid Conductor conduction Isolator Heat transfer Convection Liquid & gas solid Radiation liquid & gas vaccum page: 10 heat transfer

Conduction TB TC A = surface area (m2) TB= temperature at point B A Conduktion occurs because one particle (atom or molecule) vibrates and interacts with the neighboring atoms or molecules. A = surface area (m2) d A TB TC d = length/thickness of substance(m) TB= temperature at point B TC= temperature at point C k = thermal conductivity (W/mK) t = time (second) Speed of conduction heat page: 11 conduction

TB= temperature at point B TC= temperature at point C Convection Convection occurs because of the fluid flow that is different in density, such as refrigerator & hair drier d A fluid TC TB A = surface area (m2) TB= temperature at point B TC= temperature at point C h = coeffisien of convection (W/m2K) speed convection heat page: 12 convection

Stefan-Boltzmann’s Law = constanta of Stefan-Boltzman Radiation Radiation is one mechanism of heat transfer in the form of electromagnetic waves without passing through a medium. For example, heat of sun can reach earth. e = emissivity ( 0  e  1 ) Perfect blackbody, e = 1 Perfect whitebody, e = 0 T A Stefan-Boltzmann’s Law = constanta of Stefan-Boltzman (5,67x10-8 W/m2K4) page: 13 radiation