How can I explain to my teacher that I lost my interim? I lost my interim and its due Monday and when I tell my teacher I'm afraid she might yell at...

I believe
that the first answer to your question covers almost everything you want to know.  However, you
don't say when you lost it, if it was on the computer and you could somehow not recover it, if
you are a high school or college student, if you have lost  an assignment before in this class,
and if you have ever approached your teacher before for help or a discussion of an assignment. 
I would encourage you to rewrite the assignment or at least part of it to show good faith that
you are trying to get it done even though you lost it.  As a post-grad student, I once had to
rewrite a 20 page paper in one day as I too had lost it and knew it would not be acceptable to
turn it in late.  Needless to say, I got no sleep until it was turned in, and I never again lost
an assignment as I always made two copies immediately which helped enormously.  I wish you good
luck, and know that once can be an accident but twice is a pattern you don't want to
acquire.