Into vs. In To: One Word or Two?

Into is one word when showing movement toward or transformation: "She walked into the room." "He turned into a frog."

In to is two words when "in" belongs to a verb phrase and "to" starts an infinitive: "Log in to your account." (You log in, and "to" goes with "access.")

If you can insert "in order," you probably need two words: "Give in to temptation" → "Give in (order) to temptation." ✓