1. If - Clause

2. Form if + Simple Present, will-Future
Example: If I find her address, I will send her an invitation.
The main clause can also be at the beginning of the sentence. In this case, don't use a comma.
Example: I will send her an invitation if I find her address.
Note: Main clause and / or if clause might be negative. See Simple Present und will-Future on how to form negative sentences.
Example: If I don’t see him this afternoon, I will phone him in the evening.

3. Use
Conditional Sentences Type I refer to the future. An action in the future will only happen if a certain condition is fulfilled by that time. We don't know for sure whether the condition actually will be fulfilled or not, but the conditions seems rather realistic – so we think it is likely to happen.
Example: If I find her address, I’ll send her an invitation.
I want to send an invitation to a friend. I just have to find her address. I am quite sure, however, that I will find it.
Example: If John has the money, he will buy a Ferrari.
I know John very well and I know that he earns a lot of money and that he loves Ferraris. So I think it is very likely that sooner or later he will have the money to buy a Ferrari.

4. Form if + Simple Past, main clause with Conditional I (= would + Infinitive)
Example: If I found her address, I would send her an invitation.
The main clause can also be at the beginning of the sentence. In this case, don't use a comma.
Example: I would send her an invitation if I found her address.
Note: Main clause and / or if clause might be negative. See Simple Past und Conditional I on how to form negative sentences.
Example: If I had a lot of money, I wouldn’t stay here.
Were instead of Was
In IF Clauses Type II, we usually use ‚were‘ – even if the pronoun is I, he, she or it –.
Example: If I were you, I would not do this.

5. Use
Conditional Sentences Type II refer to situations in the present. An action could happen if the present situation were different. I don't really expect the situation to change, however. I just imagine „what would happen if …“
Example: If I found her address, I would send her an invitation.
I would like to send an invitation to a friend. I have looked everywhere for her address, but I cannot find it. So now I think it is rather unlikely that I will eventually find her address.
Example: If John had the money, he would buy a Ferrari.
I know John very well and I know that he doesn't have much money, but he loves Ferraris. He would like to own a Ferrari (in his dreams). But I think it is very unlikely that he will have the money to buy one in the near future.

6. Conditional Sentence Type I
Complete the Conditional Sentences Type I.
If you (wash) the dishes, I (cook) dinner tonight.
If my dad (have) time next week, we (paint) my room.
You (learn) a lot about American history if you (visit) the exhibition.
If the weather (be / not) too bad tomorrow, we (play) golf.
We (get / not) there on time if we (catch / not) the bus.

7. Conditional Sentence Type II
Complete the Conditional Sentences Type II.
If I (have) more time, I (learn) to play the guitar.
If she (study) harder, she (get) better marks.
If we (know) more about history, we (be / not) afraid of the test.
I (go) jogging with Tom and Sue if they (be) here this week.
It (surprise) me if she (help / not) you.

8. Conditional Sentence Type I or II
Complete the sentences with the correct form (Type I or II).
If you need the car in the afternoon, I shopping in the morning.
If I a hat, I would look like an old woman.
I'll buy this bag if they it in blue.
She wouldn't pay cash if she a credit card.
If I didn't have you, I what to do.

9. 1. If I had enough money, I (buy) a Ferrari. 2
1. If I had enough money, I (buy) a Ferrari. 2. If she studied harder, she (pass) the exam. 3. If you study hard, you (pass) the exam. 4. If we study a little every day, we (be able to) pass the exam next week. 5. If the weather is fine, we (go) swimming. 6. If John studies hard, he (get) a good mark. 7. If we go home in time, we (meet) aunt Jane. 8. If I had more money, I (be) happier than now. 9. If I were President of the United States, I (not, start) another war. 10. If I have all the luck of the world, I (win) in the lottery.

10. 11. I would be very pleased, if you (can) help me. 12
11. I would be very pleased, if you (can) help me. 12. You will get very fat, if you (eat) so many hamburgers. 13. He would catch the train, if he (walk) faster. 14. She would be much healthier, if she (not, smoke) so much. 15. They will go skiing, if there (be) enough snow. 16. You will understand what I mean, if you (read) my more carefully. 17. She would not go to school, if she (be) ill. 18. We can take a taxi, if we (miss) the train. 19. The vase will break, if you (drop) it. 20. I would not do that, if I (be) you.