Chocolate is sweetened.

It tastes bitter.

before joining word

Before chocolate is sweetened, it tastes bitter.

Explanation:

A sentence has two parts: subject and predicate. Subject focuses on the person who is doing the action and predicate talks about the action, When we join two sentences, we use conjunctions.

Conjunctions like before, after, if, because, or, but, nor and so on. In this sentence, if we want to join and sentence and make it meaningful, we would place 'before' prior to 'chocolate'. Then we would put a comma after sweetened to punctuate it properly. This would make the sentence meaningful that before the process of sweetening the chocolate, the taste of chocolate is bitter. Thus, sentence would be:

Before chocolate is sweetened, it tastes bitter.