煙 and 蒸気: smoke and vapor
Distinguish smoke from vapor without identifying a cause solely from an observed appearance.
Naming smoke
煙, read けむり, means smoke. 煙が窓から外へ出ました。 says that smoke went outside through a window.
遠くに煙が見えました。 says that smoke was visible in the distance. It does not identify what was burning.
Naming vapor
蒸気, read じょうき, means vapor or steam. 蒸気を利用する機械を見ました。 means viewing a machine that uses steam.
水蒸気 means water vapor. Do not automatically replace 蒸気 with 煙, the smoke associated with burning.
Observation and identification
白いものが見えましたが、煙かどうか分かりません。 says that something white was visible, but it was not known whether it was smoke. Observation and identification are separate.
蒸気の説明を読みましたが、装置は見ていません。 says that someone read about steam but did not see the device. Reading is not direct observation.
Does 遠くに煙が見えました identify what was burning?
Show the answer and why
No. It reports only that smoke was visible.