Specific gravity is the density of a substance compared to the density of a reference substance (usually water) Ratio. The density of a substance is the mass per unit volume. Water has a density of 1 g/mL at 4 °C.

The specific gravity of N-methylmorpholine oxide is greater than 1, which means It is denser than water. This is because N-methylmorpholine oxide is a polar molecule. The oxygen atoms in N-methylmorpholine oxide are partially negatively charged and the nitrogen atoms are partially positively charged. The positive and negative charges on the N-methylmorpholine oxide molecule attract each other, making the molecule denser.