I have given my daughter my old iphone 5. When I come to sync it how will itunes know to put her music and apps on it and not use mine

Hello christinefromcumbria,

Welcome to the Apple Support Communities!

I understand that your daughter now has your old iPhone 5 and you would like to sync it to iTunes, but are concerned about syncing multiple devices with your iTunes library. In this situation, I would advise reading over the attached article which gives a few different ways you can accomplish syncing with multiple devices.

How to use multiple iPhone, iPad, or iPod devices with one computer - Apple Support

Have a great day,

Joe