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.

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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.