change over vs turn to

change over

verb
  • to convert to, to make a transition from one system to another 

turn to

verb
  • To become, to degenerate into. 

  • To consult for advice or help. 

  • Used other than figuratively or idiomatically: see turn, to. 

  • To direct one's attention or efforts toward something. 

  • To start to do or to use something in an attempt to deal with a difficult and unpleasant situation. 

How often have the words change over and turn to occurred in a corpus of books? (source: Google Ngram Viewer )