applications - What do apps designed for small screens look like on tablets?

Do they get scaled or do they just occupy part of the screen? I mean apps that were designed for 4-5" phones running on 8-10" tablets.

UPDATE: Let me give some details to better explain my question. Given the application developer has provided one layout only (for small devices) and the app is being run on a large display. Scaling may will look terrible (especially if the scale factor is in range 2-3), because it was not designed for this, so maybe a better solution is to show a smaller version of the app in the middle of the screen. Then it will look as designed, except that it will make poor usage of the available space. However, scaling it a little bit should be fine (scale factor in range 0.8-1.5), so that the app occupies entire screen. The question is what Android is doing? Does it scale the app even if it's scaled by a large factor (over 2) or will it stop at some factor and simply place smaller version of the app in the middle of the screen?