How do we get students use what they have learned

We all know this symptom:
Kids see a flashcard and answer promptly with the phrase they have learned with it.
They hear a song and sing the lyrics~even hard ones.

30 minutes later we ask a similar or sometimes even exactly the same question outside the context and blop! 

QUESTIONMARK EYES　?

How can we help our students not falling into the Flashcard trap?

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