EXAMPLES WITH CONDITIONALS

Zero conditional 

When the result of the condition is always true, like a scientific fact.

If people eat too, much they get fat.

IF	condition	result
	present simple	present simple
If	I miss the 8 o'clock bus	I am late for work.
If	I am late for work	my boss gets angry.
If	people don't eat	they get hungry.
If	you heat ice	does it melt?

First conditional

We are talking about the future. We are thinking about a particular condition or situation in the future, and the result of this condition. There is a real possibility that this condition will happen. 

• If I have time, I will visit you.

IF	condition	result
	present simple	WILL + base verb
If	I see Mary	I will tell her.
If	Tara is free tomorrow	he will invite her.
If	they do not pass their exam	their teacher will be sad.
If	it rains tomorrow	will you stay at home?
If	it rains tomorrow	what will you do?

Second conditional

Notice that we are thinking about a future condition. We use the past simple tense to talk about the future condition. We use WOULD + base verb to talk about the future result. The important thing about the second conditional is that there is an unreal possibility that the condition will happen.

·         If I had more time, I would travel the world.

IF	condition	result
	past simple	WOULD + base verb
If	I married Mary	I would be happy.
If	Ram became rich	she would marry him.
If	it snowed next July	would you be surprised?
If	it snowed next July	what would you do?

Third conditional        

The first conditional and second conditionals talk about the future. With the third conditional we talk about the past. We talk about a condition in the past that did not happen. That is why there is no possibility for this condition. The third conditional is also like a dream, but with no possibility of the dream coming true.

• If I had had time, I would have gone to the football match.

IF	condition	result
	past perfect	WOULD HAVE + past participle
If	I had seen Mary	I would have told her.
If	Tara had been free yesterday	I would have invited her.
If	they had not passed their exam	their teacher would have been sad.
If	it had rained yesterday	would you have stayed at home?
If	it had rained yesterday	what would you have done?

http://www.englishclub.com/grammar/verbs-conditional.htm