above two equations, we have C/ min ( C) C/time ( C) ° ° ° ° Time = . min = s where ∆ l and ∆ V denote the change in length l and volume V for a change of temperature ∆ T . The relation between them is : α v = α l . The specific heat capacity of a substance is defined by s m Q = ∆ where m is the mass of the substance and ∆ Q is the heat required to change its temperature by ∆ T .
The molar specific heat capacity of a substance is defined by Q C µ where µ is the number of moles of the substance. . The latent heat of fusion ( L f ) is the heat per unit mass required to change a substance from solid into liquid at the same temperature and pressure. The latent heat of vaporisation ( L v ) is the heat per unit mass required to change a substance from liquid to the vapour state without change in the temperature and pressure.
. The three modes of heat transfer are conduction, convection and radiation. . In conduction, heat is transferred between neighbouring parts of a body through molecular collisions, without any flow of matter.
For a bar of length L and uniform cross section A with its ends maintained at temperatures T C and T D , the rate of flow of heat H is : C D H = K A − where K is the thermal conductivity of the material of the bar. . Newton’s Law of Cooling says that the rate of cooling of a body is proportional to the excess temperature of the body over the surroundings : d d Q = – k T – T t Where T is the temperature of the surrounding medium and T is the temperature of the body. POINTS TO PONDER .
The relation connecting Kelvin temperature ( T ) and the Celsius temperature t c T = t