"We’re here to put a dent in the universe. Otherwise why else even be here?" - Steve Jobs

@jeannie It will depend on what device / version you're using, but you can kill apps by double clicking on the home button, if you have one, to open the multitasking view and then swipe up / flick the app in question away to kill it. You shouldn't have to completely kill / close any apps on iOS, however.