I've been learning zero conditional, almost all examples use the example with ice cream, tutorials say that in this example we do not use article because it's in general, but I can't find any specific rule about articles in zero conditional, that says something like:
we never ever use articles in zero conditions.
For example, can I say:
If you steal car, you go to jail?
Should I say:
If you steal a car, you go to a jail?
or
If you steal a car, you go to jail?
Thanks.
Zero conditionals are for current and generally true statements. Because of that, articles that indicate specificity of situation are less likely to be used. However, that's not terribly relevant to your example.
In your example, you want the article in the first half (because "you steal car" is ungrammatical, if it's in the singular you need an article there). You want no article in the second half because you would never say "go to a jail" if you meant someone was being imprisoned. Instead, the expression "go to jail" means "be imprisoned for breaking the law". You can replace "you go to jail" as a clause with "get imprisoned for breaking the law" (get rather than be due to hard to conventions about how certain verbs are used that are not relevant to this question).
On the other hand, "if water gets cold, it becomes a solid". "When a person is hungry, they eat".
There is no general rule here. The important point is that both clauses should be general and not refer to anything more specific than they need to. The zero conditional is defined by both clauses being in the simple present tense, though many can be rephrased so the condition is in the present tense and the consequence is in some form of future tense. This shifts meaning subtly, making it a prediction rather than a statement of general fact - though it may be a prediction in which the speaker has great confidence. It also opens the possibility that a pronoun in the statement refers to a specific individual. In Babylon 5 we have the famous line,
"If you go to Z'ha'dum, you will die"
This is a prediction being made to an individual. On the other hand, if that were modified to
"If you go to Z'ha'dum, you die"
That would then be a general statement, asserting that anyone who goes to Z'ha'dum dies. However, there would be no grammatical problem with
"If you go to Z'ha'dum, you have an ice cream"
It would just be a really weird thing to say. You might also phrase that with entirely equivalent meaning as
"If a person goes to Z'ha'dum, they have an ice cream"
Or the slightly more logical
"If a person goes to an ice cream parlour, they have an ice cream"
Of course, that last one, while it makes obvious sense, isn't really true (they might get a doughnut or a coffee or something, depending on what the ice cream parlous sells other than ice cream). However, the truth or otherwise of such a statement has nothing to do with its grammatical and semantic validity.
