In a chemical reaction does matter increase, decrease, or disappear.

The answer to your question is 'No'.

Matter is never created or destroyed.  This is called
the Law of Conservation of mass.

In a chemical reaction, the amounts of matter before
and after the reaction are exactly equal.

If there's more matter there after the reaction, then the extra
came from somewhere during the reaction.

If there's less matter left after the reaction, then the rest
went somewhere during the reaction.