There are three main types of Conditional sentences:
TYPE 1: LIKELY OR PROBABLE popularly known as OPEN CONDITIONAL SENTANCES
This type of sentences implies that the action in the "IF-CLAUSE" is quite probable and if the condition is fulfilled,then the verb of main clause denotes that something will certainly take place.
In such type of sentences, the verb in the CONDITION CLAUSE is used in SIMPLE PRESENT TENSE and the verb in the MAIN CLAUSE is in the SIMPLE FUTURE TENSE.
In the case of UNIVERSAL, SCIENTIFIC Truths...the verb of the MAIN CLAUSE can either be used in SIMPLE FUTURE TENSE or in SIMPLE PRESENT TENSE. For eg:
If you heat water, it will turn to vapour.
If you heat water, it turns to vapour.
Examples with some common errors...
Wrong way: If it will rain, we will cancel the match.
Right way: If it rains, we will cancel the match.
Explanation: As mentioned above, the condition clause will always be in Simple present and not in the future tense in type 1 sentences.
Wrong way: Unless Nidhi will apologize,she will not get her job back.
Right way: Unless Nidhi apologizes, she will not get her job back.
Wrong way: He will succeed if he will work hard.
Right way: He will succeed if he works hard.
Explanation: It does not make much difference which clause comes first,although the clause you want to stress can be written first.
Wrong way: If he will invite me,I'll attend the party.
Right way: If he invites me,I;ll attend the party.