Latent heat
of fusion (solid to liquid change)
We can study
the latent heat of fusion by a simple experiment.
We should
first take a beaker and place it on a burner. A thermometer should be suspended
in it. The temperature is 0o C. When we supply heat to the beaker,
ice start melting to form water. When temperature is again noted it is still 0.
This temperature remains the same time even a little amount of ice is there in
the beaker. Till this time all heat provided is used to convert ice in water. This
heat is used up in breaking the attractive force between the ice molecules. When
no ice is left and only water is there at 0o C, any additional heat
will increase the kinetic energy of molecule thus increasing the temperature,
but before that all heat but only help in changing the state of matter.
The latent heat
of fusion of a solid is the quantity of heat in joules required to covert 1 kg solid (at its melting point) to liquid,
without any change in temperature.
Latent heat
of fusion of ice is 3.34 × 105 J/kg. 1 kg of ice at 0o
C will need 3.34 × 105 J to melt and become ice. When water at
0o C converts in ice on freezing it gives out 3.34 × 105
J of energy.
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