A small set of place prepositions - in, an, auf, and others - can take either accusative or dative, depending on whether there's movement toward a new location or a fixed position. One question decides the case every time: "Wohin?" or "Wo?"
in, an, auf, über, unter, vor, hinter, neben, zwischen
| Wohin? (to where? - movement, a destination) | → accusative |
| Wo? (where? - fixed location, no movement) | → dative |
| Movement (accusative) | Location (dative) |
|---|---|
| Ich gehe in die Küche. (I'm going into the kitchen.) | Ich bin in der Küche. (I'm in the kitchen.) |
| Ich lege das Buch auf den Tisch. (I put the book onto the table.) | Das Buch liegt auf dem Tisch. (The book is lying on the table.) |
Same preposition, same noun - the only thing that changes is whether the sentence describes arriving somewhere or already being there. This is genuinely one of the more subtle A2 points; it becomes intuitive faster by asking "wohin or wo?" out loud than by memorizing the article table alone.
Motion verbs (gehen, fahren, legen - to put/lay something down) usually signal accusative. State verbs (sein, liegen - to be lying/positioned, stehen - to be standing) usually signal dative.
Cross-checked against the Goethe-Institut A1 practice materials.