an amount of nitrogen undergoes a physical change and increases its volume. what can be known about this…

Brief Explanations:

Physical changes involve alterations in state or form without changing the substance's chemical identity. Density is mass per unit volume. When volume increases while mass remains constant (as in a physical change of a fixed - amount of substance), density changes according to the formula $\rho=\frac{m}{V}$. Boiling point is a characteristic property and doesn't change with a simple physical volume - change. Mass is conserved in physical changes. Nitrogen is a colorless gas under normal conditions and a volume change doesn't cause a color change.

Answer:

The density changed.