/Conditionals
A2Conditionals

Zero Conditional

1

What is it?

The zero conditional describes situations that are always true — scientific facts, natural laws, and general truths. Both clauses use the present simple tense. We call it "zero" because the probability is 100%: if the condition happens, the result always follows.

2

How to form it

SubjectPositiveNegativeQuestion
If + subjectIf you heat water to 100°C, it boils.If you don't sleep, you feel tired.What happens if you mix blue and yellow?
When + subjectWhen it rains, the ground gets wet.When plants don't get light, they die.What happens when you press this button?
  • • Structure: If/When + present simple, present simple
  • • The if-clause and result clause can be swapped: "Water boils if you heat it to 100°C."
  • • "When" can replace "if" in zero conditionals without changing the meaning.
  • • Use a comma after the if-clause when it comes first.
  • • No comma is needed when the result clause comes first.
3

When to use it

  1. 1

    Scientific and natural facts

    If you drop something, it falls.

  2. 2

    General truths about the world

    If you eat too much sugar, you gain weight.

  3. 3

    Instructions and procedures

    If the screen freezes, restart the device.

  4. 4

    Habits and routines

    If I miss breakfast, I feel tired by noon.

  5. 5

    Cause and effect relationships

    When metal gets hot, it expands.

4

Common mistakes

If you heat water, it will boil.

If you heat water, it boils.

Use present simple — not "will" — in both clauses for zero conditional facts.

If you will mix blue and yellow, you get green.

If you mix blue and yellow, you get green.

Never use "will" in the if-clause of a zero conditional.

When plants didn't get light, they die.

When plants don't get light, they die.

Both clauses must be in the present simple for general truths.

5

Quick reference

  • Use present simple in BOTH clauses.
  • Describes facts, laws, and things that are always true.
  • "If" and "when" are interchangeable in zero conditionals.
  • Probability is 100% — the result always follows the condition.
  • No future tense in either clause.
  • Comma after if-clause when it comes first.
6

Natural conversation example

Two students are studying for a science test.

M

Maya

What happens if you freeze water?
T

Tom

It turns into ice. That's a zero conditional — it's always true.
M

Maya

So if something is always true, we use present simple in both parts?
T

Tom

Exactly. If you mix red and blue, you always get purple.
M

Maya

And we can use "when" instead of "if"?
T

Tom

Right. "When you heat metal, it expands" means the same thing.
M

Maya

Got it. Zero conditional — zero doubt about the result!
T

Tom

Perfect way to remember it!

Practice Exercises

Fill in the blank with the correct present simple form.

  1. 1.
    If you __ (heat) ice, it melts.
  2. 2.
    When plants __ (not get) water, they die.
  3. 3.
    If you __ (mix) black and white, you get grey.
  4. 4.
    Water __ (boil) if you heat it to 100°C.
  5. 5.
    If you __ (press) that button, the alarm
  6. 6.
    When it __ (snow), the roads
  7. 7.
    If you __ (not eat), you
  8. 8.
    The machine __ (stop) if you
  9. 9.
    If you __ (add) vinegar to baking soda, it
  10. 10.
    When metal __ (get) cold, it
All TopicsFirst Conditional

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