Use if when you're not sure something will happen: If I see Ana, I'll tell her. Use when when you're sure it will: When I see Ana tomorrow, I'll tell her. Both take the Present Simple for the future, not will.
Same situation, two choices. Pick an example.
If I see Ana, I'll tell her.
The path forks: it may happen, or it may not.
When I see Ana, I'll tell her.
One path: it will happen; only the moment is open.
| Rule | If | When |
|---|---|---|
| Meaning | Maybe: you're not sure | For sure: only the time is open |
| Verb after it | Present Simple for the future | Present Simple for the future |
| Example | If it snows, the school will close. | When the film ends, we'll go for dinner. |
_____ I wake up tomorrow, I'll call you.
Paste an email or an essay. Clarigram marks the mistakes you actually make, shows the rule behind each one as a picture, and builds your practice from them.
Yes, for things that are always true (the zero conditional): If you heat ice, it melts. When you heat ice, it melts.