
The 
second conditional is used to talk about a future unreal situation, that is, there isn´t any possibility this condition will happen. On these links you have some exercises. In the
 first one you have to make second conditional sentences and the 
second one is a gap filling exercise.
Remember the
 first conditional is different in construction and use (we talk about a real possibility in the future). Let´s do
 this exercise where you have to decide what conditional is the correct one !