A change is often a response to a gradient or a differ-
ence in a property in two parts of a system. Here are
some examples of common gradients and the changes
they drive.
■
Difference in temperature—causes heat to flow
from hotter object (region) to colder object
(region).
■
Difference in pressure—causes liquid (water) or
gas (air) to flow from region of high pressure to
region of low pressure.
■
Difference in electric potential—causes electrons
to flow from high potential to low potential.
■
Difference in concentration—causes matter to
flow until concentrations in two regions are
equalized.

Measurement
An established principle in science is that observations
should be quantified as much as possible. This means
that rather than reporting that it’s a nice day out, a scien-
tist needs to define this statement with numbers. By nice,
two different people can mean two different things.
Some like hot weather. Some like lots of snow. But giving
the specifics on the temperature, humidity, pressure,
wind speed and direction, clouds, and rainfall allows
everyone to picture exactly what kind of a nice day we
are having.

For the same reason, a scientist studying the response
of dogs to loud noise wouldn’t state that the dog hates it
when it’s loud. A scientist would quantify the amount of
noise in decibels (units of sound intensity) and carefully
note the behavior and actions of the dog in response to
the sound, without making judgment about the dog’s
deep feelings. Now that you are convinced that quantify-
ing observations is a healthy practice in science, you will
probably agree that instruments and units are also useful.
In the table at the bottom of the page are the most
common properties scientists measure and common
units these properties are measured in.You don’t need to
– UNIFYING CONCEPTS AND PROCESSES–
215
COMMON UNITS OF MEASURE
Length or distance meter (about a yard)
centimeter (about half an inch)
micrometer (about the size of a cell)
nanometer (often used for wavelengths of light)
angstrom (about the size of an atom)
kilometer (about half a mile)
light-year (used for astronomical distances)
Time second, hour, year, century
Volume milliliter (about a teaspoon), liter (about
ᎏ
1
4
ᎏ
of a gallon)
Temperature degree Celsius, degree Fahrenheit, or Kelvin

Charge coulomb
Electric potential volt
Pressure atmosphere, mm of Hg, bar
Force newton
memorize these, but you can read them to become
acquainted with the ones you don’t already know.
You should also be familiar with the following devices
and instruments used by scientists:
■
balance: for measuring mass
■
graduated cylinder: for measuring volume
(always read the mark at the bottom of the
curved surface of water)
■
thermometer: for measuring temperature
■
voltmeter: for measuring potential
■
microscope: for observing very small objects,
such as cells
■
telescope: for observing very distant objects, such
as other planets

Evolution
Most students tend to associate evolution with the bio-
logical evolution of species. However, evolution is a series
of changes, either gradual or abrupt, in any type of sys-
tem. Even theories and technological designs can evolve.

Ancient cultures classified matter into fire, water,
earth, and air. This may sound naive and funny now, but it
was a start. The important thing was to ask what is matter,
and to start grouping different forms of matter in some
way. As more observations were collected, our under-
standing of matter evolved. We started out with air, fire,
earth, and water, and got to the periodic table, the structure
of the atom, and the interaction of energy and matter.
Consider how the design of cars and airplanes has
changed over time. Think of a little carriage with
crooked wheels pulled by a horse and the plane with pro-
pellers. The car and the plane have evolved as well.
So did our planet. According to theory, 200 million
years ago, all the present continents formed one super-
continent. Twenty million years later, the supercontinent
began to break apart. The Earth is still evolving, chang-
ing through time, as its plates are still moving and the
core of the Earth is still cooling.

Form and Function
There is a reason why a feather is light as a feather. In
both nature and technology, form is often related to
function. A bird’s feathers are light, enabling it to fly
more easily. Arteries spread into tiny capillaries, increas-
ing the surface area for gas exchanged. Surface area and
surface-to-volume ratio are key issues in biology and
chemistry. A cell has a relatively large surface-to-volume
ratio. If it were larger, this ratio would increase. Through
the surface, the cell regulates the transport of matter in
and out of the cell. If the cell had a bigger volume, it

would require more nutrients and produce more waste,
and the area for exchange would be insufficient. Notice
the difference between the leaves of plants that grow in
hot, dry climates and the leaves of plants in cooler, wet-
ter climates. What function do the differences in form
serve? Did you realize that a flock of birds tends to fly
forming the “V” shape, much like the tip of an arrow?
Several years ago, curved skis were brought onto the
market and have almost replaced traditional straight-
edge skis. There are countless examples of how form
develops to serve a useful function. Your job is to open
your eyes to these relationships and be prepared to make
the connections on the GED Science Exam.
This chapter has shown that there are common
threads in all areas of science and that scientists in dif-
ferent disciplines use similar techniques to observe the
patterns and changes in nature. Try to keep these key
principles in mind, since they are bound to reappear—
not only on the GED, but in your daily life as well.
– UNIFYING CONCEPTS AND PROCESSES–
216
A
LL SCIENCES ARE the same in the sense that they involve the deliberate and systematic observa-
tion of nature. Each science is not a loose branch. The branches of science connect to the same root
of objective observation, experiments based on the scientific method, and theories and conclusions
based on experimental evidence. An advance in one branch of science often contributes to advances in other sci-
ences, and sometimes to entirely new branches. For example, the development of optics led to the design of a
microscope, which led to the development of cellular biology.

Abilities Necessary for Scientific Inquiry

A good scientist is patient, curious, objective, systematic, ethical, a detailed record keeper, skeptical yet open-
minded, and an effective communicator. While certainly many scientists don’t posses all these qualities, most
strive to obtain or develop them.
CHAPTER
Science as
Inquiry
WHATEVER THEIR discipline, all scientists use similar methods
to study the natural world. In this chapter, you will learn what abilities
are necessary for scientific inquiry and what lies at the root of all
science.
22
217
Patience
Patience is a virtue for any person, but it is essential for
a person who wants to be a scientist. Much of science
involves repetition: repetition to confirm or reproduce
previous results, repetition under slightly different con-
ditions, and repetition to eliminate an unwanted vari-
able. It also involves waiting—waiting for a liquid to boil
to determine its boiling point, waiting for an animal to
fall asleep in order to study its sleep pattern, waiting for
weather conditions or a season to be right, etc. Both the
repetition and the waiting require a great deal of
patience. Results are not guaranteed, and a scientist often
goes through countless failed attempts before achieving
success. Patience and the pursuit of results in spite of dif-
ficulties are traits of a good scientist.
Curiosity
Every child asks questions about nature and life. In some
people, this curiosity continues throughout adulthood,

when it becomes possible to work systematically to sat-
isfy that curiosity with answers. Curiosity is a major drive
for scientific research, and it is what enables a scientist to
work and concentrate on the same problem over long
periods of time. It’s knowing how and why, or at least
part of the answer to these questions, that keeps a scien-
tist in the lab, on the field, in the library, or at the com-
puter for hours.
Objectivity
Objectivity is an essential trait of a true scientist. By
objectivity, we mean unbiased observation. A good sci-
entist can distinguish fact from opinion and does not let
personal views, hopes, beliefs, or societal norms interfere
with the observation of facts or reporting of experimen-
tal results. An opinion is a statement not necessarily sup-
ported by scientific data. Opinions are often based on
personal feelings or beliefs and are usually difficult, if not
impossible to measure and test. A fact is a statement
based on scientific data or objective observations. Facts
can be measured or observed, tested, and reproduced. A
well-trained scientist recognizes the importance of
reporting all results, even if they are unexpected, unde-
sirable, or inconsistent with personal views, prior
hypotheses, theories, or experimental results.
Systematic Study
Scientists who are effective experimentalists tend to
work systematically. They observe each variable inde-
pendently, and develop and adhere to rigorous experi-
mental routines or procedures. They keep consistent
track of all variables and systematically look for changes

in those variables. The tools and methods by which
changes in variables are measured or observed are kept
constant. All experiments have a clear objective. Good
scientists never lose track of the purpose of their exper-
iment and design experiments in such a way that the
amount of results is not overwhelming and that the
results obtained are not ambiguous. The scientific
method, described later in this chapter, forms a good
basis for systematic research.
Record Keeping
Good record keeping can save scientists a lot of trouble.
Most scientists find keeping a science log or journal help-
ful. The journal should describe in detail the basic
assumptions, goals, experimental techniques, equip-
ment, and procedures. It can also include results, analy-
sis of results, literature references, thoughts and ideas,
and conclusions. Any problem encountered in the labo-
ratory should also be noted in the journal, even if it is not
directly related to the experimental goals. For example, if
there is an equipment failure, it should be noted. Con-
ditions that brought about the failure and the method
used to fix it should also be described. It may not seem
immediately useful, but three years down the road, the
same failure could occur. Even if the scientist recollected
the previous occurrence of the problem, the details of the
solution would likely be forgotten and more time would
be needed to fix it. But looking back to the journal could
potentially determine the problem and provide a solu-
tion much more quickly. Scientific records should be
clear and readable, so that another scientist could follow

the thoughts and repeat the procedure described.
Records can also prove useful if there is a question about
intellectual property or ethics of the researcher.
– SCIENCE AS INQUIRY–
218
Effective Communication
Reading scientific journals, collaborating with other sci-
entists, going to conferences, and publishing scientific
papers and books are basic elements of communication
in the science community. Scientists benefit from explor-
ing science literature because they can often use tech-
niques, results, or methods published by other scientists.
In addition, new results need to be compared or con-
nected to related results published in the past, so that
someone reading or hearing about the new result can
understand its impact and context.
As many scientific branches have become interdisci-
plinary, collaboration among scientists of different
backgrounds is essential. For example, a chemist may be
able to synthesize and crystallize a protein, but analyzing
the effect of that protein on a living system requires the
training of a biologist. Rather than viewing each other as
competitors, good scientists understand that they have a
lot to gain by collaborating with scientists who have dif-
ferent strengths, training, and resources. Presenting
results at scientific conferences and in science journals is
often a fruitful and rewarding process. It opens a scien-
tific theory or experiment to discussion, criticism, and
suggestions. It is a ground for idea inception and
exchange in the science community.

Scientists also often need to communicate with those
outside the scientific community—students of science,
public figures who make decisions about funding science
projects, and journalists who report essential scientific
results to the general audience.
Skepticism and Open-Mindedness
Scientists are trained to be skeptical about what they
hear, read, and observe. Rather than automatically
accept the first proposed explanation, they search for dif-
ferent explanations and look for holes in reasoning or
experimental inconsistencies. They come up with tests
that a theory should pass if it is valid. They think of ways
in which an experiment can be improved. This is not
done maliciously. The goal is not to discredit other
researchers, but to come up with good models and an
understanding of nature.
Unreasonable skepticism, however, is not very useful.
There is a lot of room in science for open-mindedness.
If a new theory conflicts with intuition, belief, or previ-
ous established theories, but is supported by rigorously
developed experiments and can be used to make accurate
predictions, refusal to accept its validity is stubbornness,
rather than skepticism.
Ethics
Consider a chemist in the pharmaceutical company who,
after much effort, designs a chemical that can cure brain
tumors without affecting healthy brain cells. No doubt
the scientist is excited about this result and its potential
positive impact on humanity. Once in a while, however,
experimental rats given this drug die from heart failure

within minutes after the drug is administered. But since
it happens only occasionally, the scientist assumes that
it’s only a coincidence, and that those rats that died had
heart problems and would have died anyway. The scien-
tist doesn’t report these few cases to the supervisor, and
assumes that if it’s a serious problem, the FDA (Food and
Drug Administration) would discover it, and nobody
would get hurt. While the scientist has good intentions,
such as making the benefits of the new drug available to
people who need it, failing to report and further investi-
gate the potential adverse effects of the drug constitutes
negligent and unethical behavior.
Scientists are expected to report data without making
up, adjusting, downplaying, or exaggerating results. Sci-
entist are also expected to not take credit for work they
didn’t do, to obey environmental laws, and to consider
and understand the implications of use of scientific
knowledge they bring about.

Understandings about
Scientific Inquiry
Why study science? A scientist seeks to observe, under-
stand, or control the processes and laws of nature. Sci-
entists assume that nature is governed by orderly
principles. They search for these principles by making
observations. The job of a scientist is to figure out how
something works, or to explain why it works the way it
does. Looking for a pattern, for cause and effect, expla-
nation, improvement, developing theories based on
experimental results are all jobs of a scientist.

– SCIENCE AS INQUIRY–
219
The Scientific Method
There are many ways to obtain knowledge. Modern sci-
entists tend to obtain knowledge about the world by
making systematic observations. This principle is called
empiricism and is the basis of the scientific method. The
scientific method is a set of rules for asking and answer-
ing questions about science. Most scientists use the
scientific method loosely and often unconsciously.
However, the key concepts of the scientific method are
the groundwork for scientific study, and we will review
those concepts in this section.
The scientific method involves:
■
asking a specific question about a process or phe-
nomenon that can be answered by performing
experiments
■
formulating a testable hypothesis based on obser-
vations and previous results
■
designing an experiment, with a control, to test
the hypothesis
■
collecting and analyzing the results of the
experiment
■
developing a model or theory that explains the
phenomenon and is consistent with experimental

results
■
making predictions based on the model or theory
in order to test it and designing experiments that
could disprove the proposed theory
THE QUESTION
In order to understand something, a scientist must first
focus on a specific question or aspect of a problem. In
order to do that, the scientist has to clearly formulate the
question. The answer to such a question has to exist and
the possibility of obtaining it through experiment must
exist. For example, the question “Does the presence of
the moon shorten the life span of ducks on Earth?” is not
valid because it can not be answered through experi-
ment. There is no way to measure the life span of ducks on
Earth in the absence of the moon, since we have no way of
removing the moon from its orbit. Similarly, asking a
general question, such as “How do animals obtain food?”
is not very useful for gaining knowledge. This question is
too general and broad for one person to answer.
Better questions are more specific—for example,
“Does each member of a wolf pack have a set responsi-
bility or job when hunting for food?” A question that is
too general and not very useful is “Why do some people
have better memories than others?” A better, more spe-
cific question, along the same lines, is “What parts of the
brain and which brain chemicals are involved in recol-
lection of childhood memories?”
A good science question is very specific and
can be answered by performing experiments.

THE
HYPOTHESIS
After formulating a question, a scientist gathers the
information on the topic that is already available or pub-
lished, and then comes up with an educated guess or a
tentative explanation about the answer to the question.
Such an educated guess about a natural process or phe-
nomenon is called a hypothesis.
A hypothesis doesn’t have to be correct, but it should
be testable. In other words, a testable hypothesis can be
disproved through experiment, in a reasonable amount
of time, with the resources available. For example, the
statement, “Everyone has a soul mate somewhere in the
world,” is not a valid hypothesis. First, the term soul mate
is not well defined, so formulating an experiment to
determine whether two people are soul mates would be
difficult. More importantly, even if we were to agree on
what soul mate means and how to experimentally deter-
mine whether two people are soul mates, this hypothe-
sis could never be proved wrong. Any experiment
conceived would require testing every possible pair of
human beings around the world, which, considering the
population and the population growth per second, is just
not feasible.
A hypothesis doesn’t need to be correct. It only
has to be testable.
Disproving a hypothesis is not a failure. It casts away
illusions about what was previously thought to be true,
and can cause a great advance, a thought in another
direction that can bring about new ideas. Most likely, in

the process of showing that one hypothesis is wrong, a
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220