This document discusses latent heat and specific latent heat during phase changes of matter. It explains that phase changes from solid to liquid or liquid to gas occur at specific temperatures and pressures, absorbing or releasing heat. Latent heat refers to the total energy absorbed or released during a full phase change at constant temperature, such as the latent heat of fusion during melting or the latent heat of vaporization during boiling. Specific latent heat is defined as the quantity of heat energy required to change 1 kg of a substance during a phase change, such as the specific latent heat of fusion to change solid to liquid. Equations are provided to calculate heat energy involved in phase changes.

1. 4.3 UNDERSTANDING
SPECIFIC LATENT HEAT

2. CHANGE OF PHASE & LATENT HEAT
MATTER
SOLID LIQUID GAS
The change of one phase to another phase of
matter happens at a SPECIFIC TEMPERATURE
and PRESSURE. The change happens with the
ABSORPTION or RELEASE of heat followed by a
change in the volume and density of the
substance

3. LATENT HEAT(hidden heat)
Total energy absorbed or released
when a substance changes its physical
state completely at a constant
temperature.
(a)LATENT HEAT OF FUSION
The heat absorbed by melting solid
(b)LATENT HEAT OF VAPORISATION
The heat absorbed during boiling

4. FUSION (Melting)
ABSORBS
Latent heat of
fusion
VAPORISATION
(Boiling)
ABSORBS
Latent heat of
vaporisation
RELEASES RELEASES
SOLIDIFICATION
(Freezes)
CONDENSATION
(Condenses)

5. HEATING &COOLING CURVES

7. HOW TO CALCULATE?

8. SPECIFIC LATENT HEAT
Specific latent heat of fusion,l
SPECIFIC LATENT HEAT OF FUSION, l is the
quantity of heat energy required to change
1kg solid to liquid at a constant temperature.
Q=heat energy,J
m=mass,Kg
l=specific latent heat fusion,l
P=power of electric,W
t=heating time,s
If heat energy supplied by an electric immersion heater
Q=Pt
#Pt=ml

9. SPECIFIC LATENT HEAT OF
VAPORISATION,L
• Is defined as the quantity of heat energy
required to change a 1 kg liquid to vapour at a
constant temperature.
Q=ml
if supplied by immersion heater,
Q=Pt
Pt=ml

11. #When question involve change in
temperature, Q=mc<
#when question involve change in
phase,Q=ml
#when involve both use, Q=mc< and
Q=ml