Energy & Matter:1
Energy and Matter
Measuring Mass and Energy
We have discussed energy and matter in terms of the formation of the universe, but here
we will deal with these topics in a different way. As we saw in the systems lecture, how
energy and mass move through the environment is a major focus of physical geography.
Much of what we talk about for the rest of the semester will focus on these flows and
their repercussions in the natural world. Let’s start with the fundamentals of matter.
Matter is the stuff that makes up the universe. The elements are the basic types of mass
and, as you recall, elements are defined by the number of protons in the nucleus:
hydrogen has one, helium has two, carbon has six and calcium has twenty.
fundamental unit here, made up of protons and neutrons in the nucleus and electrons
whirling around the nucleus. Atoms get stuck together and form
. (Compound is usually used when the substance is a bit more complicated
and molecule when it is simpler, but let’s keep things simple and call molecules and
compounds the same thing.) Examples include water (two hydrogen and one oxygen-
O), the oxygen we breathe (two oxygen, O
), and the mineral quartz (one silica and
two oxygen, SiO
are variations in an element, caused by differing numbers of neutrons. Carbon is
a good example: almost all carbon on Earth is Carbon-12, with six protons and six
neutrons. Carbon-13 also exists, with six protons and seven neutrons. While pretty rare,
Carbon-14 exists, too, with eight neutrons. Some isotopes are unstable and undergo
. As we discussed last time, Carbon-14 is unstable and changes over
time into Nitrogen. Because we know how fast this process takes place, we can use this
radioactive decay to date objects containing unstable isotopes.
Some atoms or groups of atoms are found with a positive or negative electrical charge.
These are called
have a positive charge and
have a negative charge.
For example, hydrogen is a cation and is attracted to oxygen, which is an anion and, so,
we get water. Later in the semester, we will look at soils and see how the nutrients in the
soil tend to be cations and they are held in the soil by various anions, like clays and
Speaking of organic matter, another chemical distinction is between organic and
compounds are based on carbon and other elements–the
substances making up living tissue are organic. So is coal, for example, which is made up
of plant material buried millions of years ago. If a compound is not organic, then it is