When and if

1. We use if to say that we are not sure whether something will happen

• I'll see you in August, if I come to New York


• (perhaps I'll come to New York; perhaps I won't)

1. We use when to say that we are sure that something will happen

• We use you in August, when I come to New York.


• (I'm sure I'll come to New York)

1. We can use both if and when to talk about things that always happen.


2. There is not much different of meaning

• If/When you heat ice, it turns into water