Using Animator Controller to smoothly scale an object?

I have an object to which I want to reflect a state change with a visual adjustment - in particular, when the state changes I wish to have a subobject on that object scale up and when the state changes back I want it to scale back down. It seems like an Animator Controller is the right tool for this. So I set up a simple state machine with two states, each of which is a single-frame animation which specifies the target scale for the subobject. I then setup transitions between these two states to trigger on a boolean property and take 5 frames. I expected what I'd get would be that during those 5 frames, the scale would smoothly change; however, instead I get the scale snapping at the end of the transition.

Am I giving transitions too much credit here, can they not do this kind of thing? If not, do I need to make intermediate states which specify the 5-frame scaling up/down? (That would seem like it should work for my current 2-state setup but I am worried that in the long term that would be tough to manage with more states and possible transitions).

Thanks in advance!