opportunity and chance

According to Cambridge Academic content dictionary:

Chance is: a level of possibility that something may happen.

Opportunity is : an occasion or situation which makes it possible to do something that you want  to do or the possibility of doing something.

In some cases they both are possible to be used interchangeably.

"A chance is available in a situation where you are surprised or you had not expected it to happen. In a sentence like:

As we were in the city at the time we had a chance to visit the museum. 
Here this is something that we had not planned. In this sentence: 

If children work hard at school, they have an opportunity to go on to higher education.

Here this is something that is planned and can also lead on to something else."