If you heat ice, it melts.
If I had seen him, I would have spoken to him.
If anything changed, we would let you know.
When it rains, the grass gets wet.
If anything changes, we will let you know.
I wouldn’t have let them in, if they had been late.
Ice melts, if you heat it.
If I had some time, I would tidy up my room.
I will not let them in, if they are late again.
If I had enough money, I would go to Japan.