You should be able to (on most phones) do the following to find out the information you want.
- Go into "Settings".
- Locate and tap to open "Battery".
- Scroll down and you should find a list of apps and the percentage they are or have used.
Additionally, movies, videos, games, etc., things that have a lot of graphics, will use a lot of power.
Also, remember, that leaving apps open, even if you aren't actively using them at the time, will continue to drain the battery. So, rather than just moving to a different app, it is wise to actually close other apps when not actively using to cut down on battery drain.