Question

A block of wood 3.0cm on each side has a mass of 27g. What is the density of this block? Answer: 1.0 `"g/cm"^3`.

Answer 1

The 3.0 × 3.0 × 3.0 comes from the formula for the volume of a rectangular solid.

Explanation:

You can read about how to calculate density here.

The formula is

`"Density" = "Mass"/"Volume"`

You have to know the mass and the volume to calculate the density.

You know that the mass is 27 g.

Now you have to calculate the volume.

You know that your sample is a block that is 3.0 cm on each side.

The formula for the volume of a rectangular solid is

`V = l×w×h`

In this case, `l = w = h = "3 cm"`. So

`V = lwh = "3.0 cm × 3.0 cm × 3.0 cm" = "27 cm"^3`

`"Density" = "Mass"/"Volume" = "27 g"/("27 cm"^3) = "1.0 g/cm"^3`

In each of your calculations, the number of decimals is controlled by the number of significant figures.

Every number you use in your calculations has 2 significant figures, so you can have only 2 significant figures in your answers.