Showing Purpose

Question 1

weil, damit, um…zu

Answer 1

Weil(because) + a dependent clause shows the reason for an action; however,damitandum…zu(so that, in order to)show the goal of an action. Damit is also followed by a dependent clause, whereas um…zu introduces an infinitive.
Sie macht das Fenster zu, damit sie nicht friert. = Sie macht das Fenster zu, um nicht zu frieren.
She closes the window, so that she won’t freeze . = She closes the window, in order to not freeze.

Question 2

Common Usage:

Answer 2

Commonly, you use damit when the subject of the main clause is different from the subject of the dependent clause, and um…zu when the understood subject of the infinitive is the same as the subject of the main clause.