Terms that indicate "pay attention, we're getting ready to change"

Along with what Jeanette suggested, one of my favorite ways to cue the learner that the topic is changing is to add a visual slide transition like fade to black. Since Articulate doesn't support PPT slide transitions, I fake it by

-creating a black square the size of the slide

-cut and paste special to bring it back as a PNG

-To get the fade thru black effect, I'll add it as the last animation on the slide set to fade in. Then the first animation on the next slide to fade out.

I use transitional terminology as well, but I really think that visual element helps since we're used to feeling like something has ended when it fades to black.