Density Curriculum

Section 3—Lesson 8: How Does Atomic Mass Contribute to Density?

Understanding Goals

Subject Matter

• One cause of differences in density is the differences in the masses of different atoms.
• The mass of an atom depends upon the number of protons, neutrons and electrons that it is made up of. Protons and neutrons have a lot of mass or are especially heavy, compared to electrons.
• High atomic mass results in more mass in a given amount of space.
• Atomic mass as a cause of density applies equally to all states of matter; solid, liquid, or gas.
• We can use atomic mass to make some predictions about density differences.

Causality

• Density has multiple contributing causes. Not every cause is involved in every situation where density is in play.
• You can't compare objects or substances by using just one of the causes alone. It may leave out other important variables that contribute to the resulting density of the objects or substance. You also can't assume that every cause contributes to every situation.