Are you exclusive after one date?

I’m in college right now, and I got asked on a date later in the week by a nice guy. I don’t know this guy that well but we hit it off when we first met.

However, I have a social a day after the first date and the guy I was previously hooking up with will be there.

I don’t know if I should reject the guy I’m hooking up with after I go out on the date or if things are still open for me to hook up with other people until my date asks us to be exclusive.