The zero conditional is one of the four main forms of conditionals in English and it is the most basic type of ‘if’ sentence in this language, so we use it mainly to talk about things that we know always happen in the same way.

In this post we will learn the third conditional at level II, so the explanations are in English and the examples shown have an intermediate difficulty.

Uses of the zero conditional

We use the zero conditional for:

1. Talking about scientific facts.

If you heat pure water, it boils when it reaches 100ºC.
If you travel to space, you cannot breathe because there is no oxygen.
If you mix water and sodium, an explosive reaction occurs.
If you throw something into the air, gravity pulls it toward the ground.

2. Talking about things that always happen in the same way or to explain general facts that we take for granted.

If you mix two primary colours, you get a secondary colour.
If you don't water the plants frequently, they end up drying out.
If you sleep well at night, you don't wake up tired the next day.
If people eat a lot of junk food, they get fat and have health problems.

3. Giving direct instructions.

If you have any symptoms of the disease, go to the doctor.
If a fire breaks out in the lab, use the fire extinguisher.
If you are going to swim in the pool, take a shower first.
If the phone rings this morning, don't answer the call.

Structure of the zero conditional

Affirmative sentences

If + present simple + , + present simple

If you wake up Mary early on the weekend, she wakes up angry.
If you touch the hot ceramic hob, you get your hand burned.
If a porcelain vase falls to the ground, it breaks into many pieces.
If you add alcohol to a fire, the flames get bigger.

It’s also possible to use the same structure but inverting both clauses and eliminating the comma:

Present simple + if + present simple

Mary wakes up angry if you wake her up early on the weekend.
You get your hand burned if you touch the hot ceramic hob.
A porcelain vase will break into many pieces if it falls on the ground.
Flames get bigger if you add alcohol to a fire.

In zero conditional you can replace if with when without changing the meaning of the sentence:

Teachers get angry if students don’t do their homework.
Teachers get angry when students don’t do their homework.

Negative sentences

There are different possibilities to create negative sentences with the zero conditional depending on whether one or both clauses are in their negative form.

If + present simple (negative) + , + present simple (positive)

If + present simple (positive) + , + present simple (negative)

If + present simple (negative) + , + present simple (negative)

If you don't take the ice out of the freezer, it stays frozen.
If you take the ice out of the freezer, it doesn't stay frozen.
If you don't take the ice out of the freezer, it doesn't melt.
The ice does not melt if when is not taken out of the freezer.

As in affirmative sentences, you can use the same structure but inverting both clauses:

Ice stays frozen if you don't take it out of the freezer.
Ice doesn't stay frozen if you take it out of the freezer.
Ice doesn’t melt if you don't take it out of the freezer.
When ice is not taken out of the freezer it doesn’t melt.

Interrogative sentences

Auxiliary verb (do) + subject + present simple + if + present simple + ?

Does water vapour condense if its temperature drops below 100ºC?
Do you get purple if you mix red and blue paint?
Do you burn your skin when you don't put sun cream on summer?
Do you cross the road if the traffic light is red?

You can also invert both clauses in interrogative sentences without changing the meaning.

If + present simple + , + auxiliary verb (do) + subject + verb + ?

If water vapour temperature drops below 100ºC, does it condense?
If you mix red and blue paint, do you get purple?
When you don't put sun cream on summer, do you burn your skin?
If the traffic light is red, do you cross the road?

Zero conditional - Level II