People wonder if BECAUSE and SINCE can be used interchangeably; in most cases they can be.
BECAUSE indicates a reaction: “Because we had neglected to have our tires checked for two years, we found they were out of alignment.”
SINCE indicates either reaction or time: In the above sentence, you can substitute “since” for “because” without changing the meaning. That sentence shows cause: your tires were out of alignment as a result of not checking them for a very long time.
SINCE also indicates time: The cartoon above gives a good example of the fact that “since” can sometimes lead to an ambiguous statement. That’s something to watch out for.