The first conditional is used to talk about future situations which we think will happen or are likely to happen.  It is entirely based on the possibility that something will happen. 

The future is unpredictable. No one can be certain that anything will happen. 

The first conditional describes specific situations foreseen based on current facts. 

Sentence Structure:   if/when + present simple + will + infinitive. 

Examples

If it rains tomorrow morning, we will go to the farm in the evening. 

If we finish our work early, we will go to the supermarket.

I promised him, if he passes his exams, I will buy him a new pair of shoes. 

I have to leave soon. If I don’t hurry, I will miss the 7am train.

They will land late if the airline delays the take-off time. 

Exception: we can use unless, as long as, as soon as or in case instead of if.

Examples

I will return to work unless I don’t feel better.

The neighbor will give you the key, in case you come when I have gone out.

You can only send an email as long as you have his email address. 

She promised to cook this evening as soon as she comes back from work.

The first conditional can also be used to give advice.

For example (first conditional): If she studies harder, she’ll pass the exam (I think it’s possible she will study harder, and so she’ll pass)

First Conditional Exercises

Complete the sentences using the first conditional structure.

1. If it rains tomorrow, ____________.
2. She will be late for the party if ____________.
3. If you study hard, ____________.
4. If he doesn’t hurry, ____________.
5. They won’t come if ____________.
6. I’ll be happy if ____________.
7. If you don’t eat, ____________.
8. If she calls, ____________.
9. We won’t catch the train if ____________.
10. If they don’t leave soon, ____________.

Use the words provided to create first conditional sentences.

1. (it / rain / tomorrow) _________________________________________.
2. (she / miss / the bus) _________________________________________.
3. (you / not call / me) _________________________________________.
4. (I / not finish / my work) _________________________________________.
5. (we / have / a picnic) _________________________________________.

Click here to do more exercises on the zero conditional and other English grammar points.