Question

There is water on the pan of the scale as you measure the mass of a mineral. If you were to ignore the water, what would the effect on your density calculation?

Answer 1

The scale measures the mass of a substance and density is mass per unit volume. If the volume is already measured, then ignoring the weight of the water in the pan would decrease the mass being divided by the same amount of volume. This would result in a smaller value for density. For example:
Mass of mineral + water = 10 g
Volume = 10 cubic centimeters
Mass of mineral alone = 8 g
Before removing water, the density would work out to be
10/10 = 1 g / cm^3
However, if we remove the water,
8/10 = 0.8 g / cm^3