Category posts only in category to which they belo

So sorry if this has been answered before, but I’ve looked everywhere. Obviously, the index page shows the ‘Home’ category posts when you first enter the site or just call index.php. Unfortunately, it also shows posts to every other category you’ve posted in if you just call index.php – whether you want them shown or not.
Is there a simple way to make index.php show ONLY the posts you’ve specifically assigned to ‘Home’ – cat=1?
Please say yes. ?? I don’t want to rename this page everywhere and make a stand-alone index page to solve this.