The Zero Conditional Clause
Use:
*We use it when the result is always true.It describes facts.
Form:
If +present simple--------,present simple.
EX:If we boil water,it evaporates.
*We use (when ) instead of (If) with no change in meaning:
EX:When we boil water,it evaporates.
Ex:If you touch a fire,you get burnt.It is true.
*It is natural to put (If/when) in the middle of the sentence:
EX:You get burnt when you touch a fire.
The First Conditional Clause
Use:
We use it to talk about possible situations in the future.In real,we don't know what will happen in the future.It might be true.
Form:
If+present simple---------,future simple(will+inf).
EX:If I have a lot of money,I will help the poor people.
EX:He will miss the train If he gets up late.
Notice: The zero conditional is used to talk about general situations but the first conditional is used to talk about particular situation.
The Second Conditional Clause
Form:
If +past simple----------------,would + inf
Use:
1-It is used to talk about impossible things in the present because it is not true:
EX:If I found the key,I would open the door.It is impossible now to open the door because I don't have the key.
2-It is also used to talk about improbable situations in the future.I imagine things.
EX:If he studied hard ,he would pass the exam.It is improbable because I think he won't study.It only depends on my expectations.
EX:If I were a bird ,I would fly.I only imagine so it is impossible to happen.It is not true.
3-We use the second conditional to give advice:
EX:If I were you ,I would see a doctor.
The Third conditional Clause
Form:
If+past participle---------------,would have +p.p
Use:
It is used to talk about finished situations so we can't change any things in the past.We imagine the result of this situation.It expresses sorrowful.
EX:If I had studied hard ,I would have passed the exam.
Here he examined and failed the exam.He regretted not studying.He imagines the result of studying hard.
EX:If we hadn't got up late ,We wouldn't have missed the bus.Here we got up late and missed the bus.We only blame ourselves for not getting up early.