Each some what tells the same meaning but the places we use that differs .
therefore means because of that . it is used in the places of ajective adverb etc...
example ; she is white because she lives in america
since;indicates the situation or time it is mostly used in the places of verb and in the form of complex sentences
example ; since there was no time i dint come to park
hence ; means because of that it can be used instead of where we use since
example ; hence there was no time i dint come to park
so ; indicates action mostly used instead of therefore it comes in passive voice
example ; she lives in america so she is white