Learn German: Sie hat die ganze Leinwand bemalt. - She painted the entire canvas.

The prefix be- often shifts the focus of an action to the surface or object being affected. While malen means to paint a picture or create art, bemalen means to apply paint onto a surface or cover something in paint. Because she is covering the canvas itself, bemalen is the perfect choice.

Does the prefix be- change how the verb interacts with objects?

Yes! Verbs with the be- prefix are almost always transitive, meaning they take a direct object in the accusative case. It also changes what that object is. With malen, the direct object is the artwork being created (like a picture). With bemalen, the direct object becomes the surface receiving the paint, which in this sentence is die ganze Leinwand.

Why does the adjective ganze end in "-e"?

This is an example of weak adjective declension. Because the feminine accusative noun Leinwand is preceded by the definite article die, the adjective ganz just needs the basic -e ending.

I've seen Leinwand used in a different context. What else can it mean?