A metal object has a mass of 1450 g and displaces 542 mL of water rumors. Calculate the density of this object.

Answer 1

Hi Maddy,

Density is a curious property. Everyone has a feeling for it, and an intuitive understanding of it. If you pick up a peanut in a shell, and pick up a rock that's about the same size, you understand from the weight of the two objects that one of them (the rock) has a lot more mass packed into it than the peanut does. Some materials are VERY dense (most metals, for example) and some materials have very low density (foam rubber or styrofoam, for example.

With a little division, we can compare the density of any two objects, as long as we know their mass and their volume. In our experiment above, we compared two objects that had very similar sizes (volumes), so we didn't have to do any division or math at all to know that the rock was more dense than the peanut.

Density is the amount of mass in some unit of volume, or we could say "mass per volume". Whenever you see "per" in a description, think "division"... in this case, mass divided by volume. That is the key here.

And volume, here, is measured as the measure of water displaced by this metal object. Fill up a container of water to the brim, put in a metal object, and 542 mL of water spills out of the container (ie, 542 mL is displaced by the metal object). One 1 mL of water is also called a cubic centimeter (cm³). So the density of this material is:

1450g / 542mL = 2.68 g/mL or g/cm³

Hope that helps!