"Ποιος είναι ο χαλκός;"

[romualdGyorgy]

The correct (English) version of this sentence suggests that we don't know what copper is; that's why we are asking.

However, from the Greek sentence I understand Which one is the copper?. I would ask this question in the presence of a few metal objects to find out which one is made of copper.

I would have expected to see τι instead of ποιος here. Why is ποιος used?

[troll1995]

You are right. The sentence was wrong. It is fixed now! Thank you!

[robert672165]

I'm surprised. Cyprus, and many English words, derive from what I thought was the Greek word for copper. Am I wrong, or is this just another example of the evolution of Greek?

[joeTatt1]

The original Latin word for copper was æs, but that word was extended to its alloy with tin, bronze, and as this was far more extensively used than pure Copper, the word's primary sense shifted to the alloy and a new word evolved for Copper, from the Latin form of the name of the island of Cyprus (in Greek Κυπρος [Kypros]), where copper was mined: Cyprium (æs) (Greek: χαλκος κυπριος [chalkos kuprios]). 
http://www.vanderkrogt.net/elements/element.php?sym=Cu

[isadoros]

Doesn't ποιοσ denote a person "who is copper" literally translated.

[D_..]

No, ποιος/ποια/ποιο are used for people and things alike, meaning who or which depending on what you're talking about. You just need to match the gender of the pronoun with that of the word it's replacing.

[involans]

I would have expected "Which one is the copper one"

[J.N7MH]

Or "Which is the copper one?" The translation you give is not proper English.

[G.Georgopoulos]

That requires an adjective: Ποιος είναι ο χάλκινος; / Ποια είναι η χάλκινη; / Ποιο είναι το χάλκινο;

A more natural English translation has also been included in the alternatives.