My iphone4S heats up whenever i use Location services for a prolonged period or use Data over 3G or 2G network. Is it Normal?

My iphone4S heats up whenever i use Location services for a prolonged period or use Data over 3G or 2G network. Is it Normal? i have been noticing this for some time now. Whenever i use 3G or 2G data the phone tends to heat up near the place where the SIM chip is inserted. Also while using apps which use location services the phone heats up which can be noticed by touching the metal part on the sides of the phone. is this Normal ?