Change Of State and Latent Heat Video Lecture | Physics for JEE Main & Advanced

change of state and specific latent heat
specific latent heat is the amount of
heat energy required to change the state
of a unit mass of a substance without
change in temperature the word latent
means dormant or concealed let's perform
an activity to find out why the heat
energy required to bring about a change
of state is called latent heat take some
ice cubes in a beaker suspend a
thermometer into the ice cubes and note
its temperature the temperature is zero
degree centigrade heat the ice cubes
record the temperature after every
minute
keep stirring the ice water mixture
constantly so that the temperature is
uniform throughout we observe that the
thermometer reading remains constant at
zero degree centigrade though heat is
being constantly supplied the
temperature remains constant till the
ice completely melts to water at zero
degree centigrade continue heating water
which is at zero degree centigrade we
observe that the temperature is
increasing record the rise in
temperature till the water starts
boiling continue heating the boiling
water gets converted to steam observe
that the thermometer reading remains
constant at hundred degree centigrade
which is the boiling point of water that
is there is no change in temperature
this shows that the temperature remains
constant whenever there is a change of
state what happens to the energy
supplied the energy supplied is used to
break the intermolecular force of
attraction existing between the
molecules and therefore the thermometer
does not register a rise in temperature
whenever there is a change of state
since the energy supplied is not
recorded in the thermometer the heat
supplied is called latent heat craft
shown here represents the changes taking
place when ice at zero degrees
centigrade is heated