How to track changes in Sandbox?

We had a contractor working in our Sandbox to add features to our Salesforce system. Well, the contract hours ran out and the contractor has gone. Now we are stuck with a bunch of changes done in our Sandbox that need to be identifiied, tested and moved to production. The changes could have been adding fields, objects, trigger and APEX code. We don't know.

Is there a way to compare the non-data structure of our Sandbox against production to see what are the differences?

Thanks for any help.