Answer
1. "Parting is such sweet sorrow" (Act 2, Scene 2) - This oxymoron highlights the conflicting emotions of love and sadness that Romeo and Juliet feel as they part.
2. "Feather of lead" (Act 1, Scene 1) - This oxymoron emphasizes the heavy burden of Romeo and Juliet's forbidden love.
3. "Cold fire" (Act 1, Scene 5) - This oxymoron symbolizes the passionate yet forbidden love between Romeo and Juliet.
4. "Heavy lightness" (Act 2, Scene 4) - This oxymoron conveys the conflicting emotions of joy and sorrow that Romeo and Juliet experience as they fall in love.
5. "Bright smoke" (Act 3, Scene 2) - This oxymoron symbolizes the fragility of Romeo and Juliet's love, which is both beautiful and fleeting.
The use of oxymorons in Romeo and Juliet deepens the play's themes of love, sorrow, and tragedy, emphasizing the conflicting emotions of the characters and the fragility of their love.