Form
If + Subject + Present Simple, Subject + Present Simple.
If you heat water to 100°C, it boils.
If I drink too much coffee, I get a headache.
Meanings
General Truths & Scientific Facts
We use the Zero Conditional to talk about things that are always true. The result of the ‘if’ clause is always the same. This is why it is often used for scientific facts, general truths, and habits.
Scientific Fact: If you freeze water, it becomes ice.
Habit: If I miss the 8 AM bus, I am late for work.