Safety Precaution Take care when handling hot apparatus.
Notes
As with finding the specific heat capacity of water by electrical method, a voltmeter, ammeter and stopwatch can be used instead of a joulemeter to calculate the energy supplied. Glycerol is used (i) because of its high boiling point, (ii) because it allows for efficient heat transfer to the metal and (iii) because it allows for an accurate reading of temperature of the metal.
Boiling point
Latent heat of vapo- risation
Melting point
Latent heat of fusion
Energy supplied / J Fig 9.5: Graph illustrating latent heat Specific Latent Heat
SPECIFIC LATENT HEAT The specific latent heat (l ) of a substance is the amount of heat required to change the state of 1 kg of the substance without a change in temperature.
It is a scalar quantity with an SI unit of joule per kilogram (J kg1). heat mass specific latent heat
SPECIFIC LATENT HEAT
Q ml Q energy (supplied or withdrawn),m mass of body, l specific latent heat
Specific Latent Heat of Fusion
SPECIFIC LATENT HEAT OF FUSION The specific latent heat of fusion (lf) of a substance is the amount of heat required to change 1 kg of the substance from a solid to a liquid without a change in
temperature.
The specific latent heat of fusion of ice should be noted, but will be given to you if required in the Leaving Cert. examination.
lfice 3.3 105 J kg1 140 INVESTIGATING PHYSICS As it is a form of heat energy, it’s a scalar quantity with an SI unit of joule ( J). Latent Heat LATENT HEAT
The Latent Heat (L) of a body is the amount of heat required to change its state without a change in temperature.
