Discuss significant changes that happen in Chapter 9 of Animal Farm.

I think that one of the most profound changes in Chapter 9
is that Boxer is permanently injured while working and is carted off to the Knacker's. 
It is there where he dies.  This is one of the most intense changes because Boxer, along
with Clover, had been one of the most staunch and loyal followers of the Revolution. 
His commitment never wavered with his work ethic, his trust, and his fundamental desire
to "work harder" or believe that "Napoleon is always right."  His death creates a void
that ends up being phased out or airbrushed over time, but is one that is felt
powerfully in the reader's mind.

I think that this helps to
bring about another significant change in the characters.  In the scene where Boxer
dies, all the animals gather to say their farewells to him.  Yet, after this, some
unsettling feeling hits them all and Muriel starts to spell out the words on the side of
the truck that is taking Boxer away.  She proceeds slowly, but is interrupted by, of all
animals, Benjamin.  It is Benjamin who tells all of the animals where Boxer is going and
what is going to happen to him.  Benjamin's character up to this point had been a
disassociated skeptic, cynical of everything and good for responses that only indicated
futility.  It is this moment where Benjamin is seen as a force of change, an agent of
transformation, and someone who wants more out of life than what has been given.  It
comes too late, as he is unable to save the life of his best friend, but is a change,
nevertheless.

Outside of Boxer's death, there are other
changes in the farm.  The animals are getting older, and while there was talk of
retirement and full salary and benefits, nothing of the sort actually happens.  In fact,
the farm becomes infused with a "youth movement" of pigs, with Napoleon as their
presumed father.  Most of the animals have forgotten about Jones, which is a reflection
of how much things have changed.  Moses, the raven, has also returned to resume his
sermons about "Sugarcandy Mountain."  His presence is still criticized by the pigs, but
is given an allowance of beer to stay and continue on with his
sermons.