Can I switch two numbers between 2 iphones?

My mom has the iPhone 5 and I have the iPhone 4 and she wants my phone instead and I want hers. Is it possible to switch numbers on both sim cards so I'd have the 5 with my number and she'd have the 4 with her number?

The phone numbers are linked to the sim cards instead of the phones themselves. You won't be able to easily swap phones because the iphone 5 requires a nano instead of a micro sim card. You will notice when trying to switch them out that they will not fit. You will need to go to the cell phone store to have them switch it for you, which may or may not end up costing you money.