Which property remains constant for a given substance regardless of sample size?

• A. Mass
• B. Colour
• C. Volume
• D. Density

Answer: (B)

Think about how properties behave when you change how much of a substance you have. Mass and volume scale with amount—more substance means more mass and more volume. Density, which is mass per unit volume, is an intensive property: it doesn't depend on the amount of material. If temperature and pressure stay the same, the same substance has the same density whether you have a tiny sample or a large one. Color is also an intensive property and usually stays the same for a pure substance, but the standard point here is that density remains constant regardless of sample size because it’s the intrinsic ratio of mass to volume. So the property that stays constant is density.