Use the zero conditional for things that are always or generally true: facts, rules and habits. If you heat ice, it melts. If I drink coffee late, I can't sleep. Form: if + Present Simple, Present Simple. Here if means almost the same as when or whenever.
If you heat ice, it melts.
No imagined world here, just the real path. Every time the condition happens, the result follows.
| The if-part | if + Present Simple: If you heat ice |
|---|---|
| The result | Present Simple: it melts |
| Instead of if | when or whenever, with the same meaning: When you heat ice, it melts. |
| Order | Either part can come first. Use a comma when the if-part comes first: Ice melts if you heat it. |
If you mix red and blue, you get purple.
Things that are always true, every time.
If I work late, I take a taxi home.
What usually happens in your life when the condition is true.
If the alarm rings, leave the building.
The result can be an instruction (an imperative).
Common expressions worth learning as they are.
If you _____ water to 100°C, it boils.
From always true to an imagined past.
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.
Zero for what's always true (If you heat ice, it melts). First for one particular situation in the future (If you leave the ice cream in the sun, it'll melt).
In the zero conditional, yes: they mean almost the same. In the first conditional they're different: if means maybe, when means you're sure it will happen.