The use of the verb "know" in the sense of knowing the name of something

Question

Let's say I want to know if someone knows the name of something, say, the capital of a country. Would it be natural to say the following?

Do you know the capital of Japan?

Would it be more natural to say it in the following way?

Do you know what the capital of Japan is?

I feel that if someone asks do you know the capital of a country? that could mean that the person wants to know if the other person have been there and knows their way around it, its culture etc. Tell me please if there is any truth to that? If both sentences are fine, which structure is more common?

Answer 1

The meaning of Do you know X? is inherently ambiguous / imprecise. It could mean Are you aware that X exists?, OR Are you [very] knowledgeable about X? ("Are you personally acquainted?" if X is a person, "Do you fully understand?" if X is a concept, etc.).

So even native speakers are sometimes unsure about exactly what they're being asked (but usually the context gives sufficient clues). It might seem a bit odd to a non-native speaker, but the following conversation is actually perfectly credible...

A: You know the capital of Japan? I hear the mayor is planning to build a spaceport in the city centre!
B: Yeah, I read about that. I can't remember the name of the Japanese capital though. Do you know it?
A: No, I don't know the actual name. Didn't it used to be called Saigon, or something like that?
B: Maybe. But they might have changed the name to Peking after the war.

...where A's first sentence simply means something along the lines of I'm sure you're aware that Japan has a capital city. Focus on that, because I'm going to say something about it. But obviously neither A nor B know much at all about the capital of Japan - not even the name (all they know is it's planning a spaceport).

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In practice, OP's first (shorter) version is a far more common way of asking whether someone knows the name of something. If the questioner wanted to ask whether the addressee was intimately familiar with the capital of Japan (through having spent some time visiting / living in Tokyo), he could unambiguously indicate that by asking Do you really know the capital of Japan?

Thus broadly speaking,...

1: Do you know the capital of Japan?
...might mean anything from...
1a: The capital of Japan is the focus of my next statement (but it's irrelevant whether you know its name)
...through...
1b: Do you know the name of the capital of Japan?
...to...
1c: Do you know [in detail] what the capital of Japan is like?

Answer 2

There are three common ways to ask for the name of something

What is the name of the capital of Chad?

What is the capital of Chad called?

What is the capital of Chad?

Notice that none uses the verb "know." The third uses ellipsis by dropping the participle "called." Dropping "called," "named," "denoted," and similar verbs that refer to labeling is a permissible and very common blurring of the distinction between use and mention. That distinction should not be blurred when using "know," which is not itself a verb of labeling.

Do you know the capital of Japan?

does not ask for a name. In fact, it is not clear at all what it is asking. It might get construed as

Do you know what X is called?

but it is far more likely to be construed as

How familiar are you with Tokyo?