Heat

Heat

In daily life very much found the use of energy in the form of heat
o Cooking food
o Space heating / cooling, etc..

Heat is the transfer of energy from one object to another object because of differences intemperature. In SI units, the unit is the joule heat with 1 cal = 4186 J 1 calorie (cal) = heatrequired to raise the temperature of 1 gram of water by 1^oC
The amount of heat required to change the temperature of a system
Q = m C ΔT
m = mass (g)
c = heat type (kal/g^oC)
ΔT = temperature change (⁰C)

If different parts of the isolated system are at different temperatures, heat will flow fromhigh to low temperature If the system is completely isolated, no energy can flow into or out,then apply conservation of energy by
Qserap = Qlepas

Phase Changes
Substance can be solid, liquid or gas. When there is a phase change, a number of heatreleased or absorbed by a substance that is
Q = mL
Q = heat (calories)
m = mass (g)
L = latent heat (cal / g)
Heat of fusion of ice 0oC = 80 cal / g
100oC Heat of vaporization of water = 530 cal / g

Heat Transfer
Heat of wrought or move from one object to another
in three ways:
1. conduction
2. convection
3. radiation

Conduction
Transfer of heat from one place to another by means of collisions between molecules, withthe rate
heat flow
K = thermal conductivity (J / s.m. C)
A = cross-sectional area (m2)
T = Temperature (0C)
L = Thickness / length (m)

Convection
Heat is transferred from one place to another by the movement of molecules, substancesor materials

Radiation
VeloCity of an object radiating energy / stefan-Boltzmann equation