Learn Hardcore Russian: В нашей семье рецепты передаются от бабушки детям. - In our family, recipes are passed down from grandmother to children.

The preposition в meaning “in” requires the prepositional case to indicate location. The noun семья (family) changes to семье in that case. Its modifying adjective наша also follows the prepositional feminine declension pattern and becomes нашей. So:

наша семья (nom.) → в нашей семье (prep.)

What case is рецепты in, and why is it the subject of the sentence?

рецепты is in the nominative plural because it is the grammatical subject—the thing that “is being passed down.” In Russian, the subject of a clause normally stands in the nominative case.

Why is the verb передаются used instead of передают, and what does the -ся ending do?

передаются is the reflexive/passive form of передавать (“to pass on”). Adding -ся turns it into “are passed on,” so the focus is on the recipes themselves rather than on who does the passing. Without -ся, передают would be active voice: “(they) pass on.”

Why do we say от бабушки (genitive) and детям (dative) to mark “from grandma to the children”?

The preposition от (“from”) requires the genitive case, so бабушка becomes бабушки.
The dative case marks the recipient of the action, so дети becomes детям.
Together they express “from grandma” → от бабушки, and “to the children” → детям.

Could we use the instrumental case бабушкой instead of от бабушки?

Yes, in a true passive construction Russian can use the instrumental to indicate the agent:
• Рецепты передаются бабушкой детям.
This is grammatically correct but less idiomatic. Using от бабушки (genitive + preposition) is more common when talking about traditions “coming from” someone.

Why not simply say бабушка передаёт рецепты детям (active voice)?

Both are correct, but the passive/reflexive передаются shifts the focus away from the person doing the action and onto the recipes themselves as part of a family tradition. The active version emphasizes бабушка as the agent, while the passive emphasizes the process of transmission.