WHEN A CANDLE BURNS, BOTH PHYSICAL AND CHEMICAL CHANGES OCCUR. WHAT ARE THESE CHANGES?THIS A QUESTION BASED ON CHEMISTRY.

 
the heat of thecandle flame first melts the
wax, and it rises up the candle wick by capillary action.  Farther up the wick, the
greater heat vaporizes the wax molecules, which move from the wick into the surrounding
space.  The heat of
the flame and reactive molecules (free radicals) in the
flame break apart the wax molecules, in particular stripping hydrogen atoms from the
carbon-chain backbone.  Some of the carbon chains fragment into gaseous carbon (C2) and
into small (typically two-carbon atom containing) molecules
and molecular
fragments.  The hydrogen atoms stripped from the

wax
molecules
eventually combine with oxygen atoms from the air to form water
molecules.The carbon atoms eventually combine with oxygen to form carbon monoxide and
carbon dioxide, but first many of them combine to form very large (as far
as
molecules are concerned) clumps of carbon-rich solid material, called
soot.Some of this soot burns to make carbon dioxide in the candle flame,
and
sometimes some of it escapes the flame.*  Several zones of a candle flame
can be seen with the eye.  At the bottom  
is a region that gives off blue
light.  This light is actually molecular emission from gaseous carbon, C2.  Further up
the flame is a region that is substantially opaque and which gives off yellow light. 
This is known as the
"incandescent region", and is where hot soot particles
glow,
giving off
light like the filament of a light bulb. The inside
part of the flame, near
the wick, is oxygen-deficient, and most of the
reactions that occur are
heat-induced fragmentations and rearrangements.  In
the outer regions, where
oxygen can enter from the surrounding air, the
fragments combine with
oxygen, eventually forming water and carbon
dioxide.