HEAT

In physics, heat is defined as the energy flowing from the hotter bodies to the colder bodies where they are in contact with each other until their temperature are identical and thermal equilibrium.
Basically, heat is a form of associated with the motion of atoms, molecules, and other particles. Which comprise a matter. Heat can be produced by chemical reactions, nuclear reactions, electromagnetic dissipation (such as in electric stovel ) and mechanical dissipation (such as friction).

Specific Heat and Heat Capacity

According to Joseph Black, the temperature increase of an object can be used to determine the heat conserved by the object.
In this case the amount of heat required by an object to change its temperature of 1C or 1 K is called heat capacity. Therefore the relation of heat, heat capacity, and change of temperature of an object can be expressed :

Another equation of heat required by an object in relation with the object’s mass is : Q=m.c.ΔT
Where :
Q = heat / kalorie (joule)
m = mass of object (kg)
c = spesific heat (J / kg)
ΔT = change of temperature (K)

In this case, the spesific heat (c) is the amount of heat (in calories), that is required to raise the temperature of one gram of a substance one degree celcius or one kelvin.

B.Conservation Energy Law for Heat


Conservation energy law for heat complies the principle proposed by Joseph Black, that is in the mixing of to substance the amount of heat released by the substance with higher temperature is equal to the amount of heat absorbed by the substance with lower temperature. This statement often called. The Black’s Principle and can be expressed :
According to the Blacks principle then the heat exchanged in substance can be determined by measuring the specific heat of the substance using calorimeter.
Conservation energy law for hat is only vlid in the closed system.

Sample Problem :
1. A Piece of metal of 500 gram in mass and temperature of 80C is immersed (dimasukkan) in to 1 kg water which its temperature is 20C. After the balanced state the mixture temperature becomes 23C. If the specific heat of water is 1 cal/grC. Calculate the specific heat of metal?


C. Changed of phase and latent Heat :
The changed of phase of a substance is caused by the substance release or absorb heat. The change of phase of a substance caused by the substance releasing heat are condensation, freezing and deposing (deposit )
While the change of phase of a substance caused by the substance absorbing heat are evaporating (boiling), meting and sublimation.