Chem One Online Support Course

Module # 1
Topics and Concepts
Page 8


Solutions to Problems
Reports
Laboratory
Program Downloads

Density:

What is the definition of density? Maybe it is best thought of as the degree or extent of compactness.

We have all gone on vacations both long and short. We pack differently for long vacations than for short ones. The biggest difference is that we take more clothes for long vacations.
What would happen if you were limited to only one suit case (medium size) for a 4 week vacation?
You would try to pack as much as possible into the suit case. You may even try to sit on the top of the case to squash things down so that you can fit more. The more you squash the more you can put into the suitcase. But when you finally get ready to carry the suitcase you realize that it is very heavy.

You have put more material (clothes) in a small volume (suitcase) that was not made for so much material (clothes) so that it is now quite heavy. In scientific jargon you have increased the density or degree of compactness of the contents of the suitcase.

There are two basic things that can make a suitcase heavy.

  • The weight of the clothes you put in it.
  • How well you can squash things together.

These are the same two things that contribute to the density of elements. How much mass an atom of an element has and how close the atoms can be squashed together.

Units of Density:

Density is a derived quantity. That is: It is a quantity that is not directly measured but is derived or calculated from the measurement of two other properties which are Mass and Volume.

The formula for Density is D = M/V

Thus mathematically, density is the measure of the amount of mass that occupies a certain volume.

Things with high density have more mass occupying a certain volume. That large mass might come from the fact that the thing weights a lot or it may come from the fact that more things are easily squashed into a small space or both.

There are two standard ways of expressing units of density.

Grams/milliliter or g/ml

Grams/cubic centimeter or g/cm3

Of course other units can be used as long as there is a unit of mass divided by a unit of volume. Thus you may have density expressed in a variety of different units.

decigrams/dekameter or dg/dam3

Kilograms/cubic millimeter or kg/mm3

Again we have an ideal opportunity to practice our metric conversion skills by changing the units of density into a variety of other equivalent units.

You will find Examples of density conversion problems in the Example Problems Pages of this Web Site. Use the side bar to link to the Example Pages and choose Density Conversions.

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