Why is the density expressed in two significant figures?

Answer 1

It is not always expressed in 2 sig figs. The number of sig figs depends on the accuracy of your measurements of mass and volume to calculate the density as well as any variables that you are expected to use the density with. There is no point in having a density expressed to 15 significant figures if then you are going to multiply it by volume expressed to 1 sig fig to determine the mass.

Answer 2

Expressing density in two significant figures helps to maintain the accuracy of the measurement while also keeping the data concise and easy to interpret. It strikes a balance between providing enough precision without overwhelming with excessive decimal places.