Q: iPhone 4s gets hot when using it

The iPhone's enclosure is actually designed to draw out heat from the internal components; in order to keep the internal parts of your phone cool. It will get pretty warm, but should not burn you, or be too hot to hold or use.

See article below for more information about acceptable operating temperatures for your iPhone 4S.

http://support.apple.com/kb/HT2101

It's normal to get warm-hot. "Quite-hot" is subjective, and no one here could say that's "too hot."  If in doubt, take it back to Apple or whoever provides iPhone warranty service for you.