C. A new substance is produced. All others are physical changes.
In order to answer this, you need to find the empirical data for the standard entropies. Please refer to this link: http://www.mrbigler.com/misc/energy-of-formation.PDF
For NO₂ gas, the entropy is 240 J/mol-K. For N₂O₄ gas, the entropy is 304.2 J/mol-K. Therefore, <em>the statement is false.</em>
Bright Line Emission Spectrum: As the excited electron returns to ground state (it's lower energy level) the energy it originally absorbed is released as discrete lines of light.
Water, lower, and I'm not too sure for the third one... sorry.
