Chemistry is the study of the composition,
properties, and interactions of matter. Matter
is anything that occupies volume and has a
mass. Essentially, chemistry is studying what
matter is made up of, what it is like, and
what happens when different things encounter
each other.
Chemistry is often called the central science
because of all of the fields it is related
to. Some of these fields include nuclear chemistry,
environmental science, food science, and materials
science. It is likely that your major is not
chemistry, but you will need chemistry in
each of your careers.
In this class, we will primarily be learning
things that are already known; they have already
been discovered. We need to keep in mind as
we learn them the way that they were discovered
– using the scientific method. The scientific
method is a circuitous process, but it involves
four main things: observations, hypotheses,
theories, and laws. Consistently seen observations
can become laws, and consistently confirmed
hypotheses can become theories. Confirmed
hypotheses can give us information that allows
us to make new hypotheses, so scientific testing
keeps moving forward. Let’s look at each
of the four parts of the scientific method
in more detail.
Observations can either be random or through
experiment. A random observation could be
you walking down the sidewalk and noticing
a particular feature about a tree that you
see. Most observations need to be set up in
a controlled way for a specific set of results,
so scientists set up experiments which allow
them to gather data. Whether random or through
experiment, you are using your senses to tell
you something about the world. Observations
answer the question “what?”: “what is
happening in the world; what is the world
like?” An example of an observation is that
someone you know who is a milkmaid did not
contract smallpox. Another example would be
that a ball was dropped and had an acceleration
of 9.8 m/s^2.
When you observe the same thing over and over
again, you can summarize those observations
with a law. Laws give us patterns or trends
in observations and summarize things that
always happen. Laws still answer the question
“what?”: “what is happening in the world;
what is the world like?” For example, if
none of the milkmaids you know get smallpox,
you could express that as a law: all milkmaids
do not get smallpox. Another example of a
law would be F = ma (force equals mass times
accelelration).
A hypothesis is a tentative explanation for
observations. It is tentative, meaning we
are unsure; it is a guess. A hypothesis has
either not been tested at all or has not been
sufficiently tested to be confident about
its truth. A hypothesis answers the question
“why?”: “why do things happen the way
they do?” To be a good hypothesis, it should
be specific and testable. It should be falsifiable—there
should be some potential result which would
show the hypothesis to not be true. A good
way to express a hypothesis is as an if-then
statement. An example of a hypothesis is that
milkmaids do not contract smallpox because
they have already been exposed to cowpox.
Another way of saying that is that if a milkmaid
is exposed to cowpox, she will not contract
smallpox. This is falsifiable: if we expose
a milkmaid to cowpox and she gets smallpox
anyways, our hypothesis has been proven false.
Another example of a hypothesis is that apples
fall from trees because of gravity. We could
set this up as an if-then statement as well:
If I move an apple to outer space where there
is no gravity, then it should not fall. Again,
this would be falsified if it fell even when
there was no gravity.
The word “theory” is overused and misunderstood.
Often when people say “I have a theory”
they really mean “I have a hypothesis”
because they haven’t tested it yet. A scientific
theory is a hypothesis that has been confirmed
over and over again.
Please watch the video linked in this slide
about the difference between a law and a theory.
Throughout the semester, I will be asking
you poll questions. After I finish reading
and/or instructing about each question, please
pause the video and try to complete the question
on your own. On the following slide, I will
give a brief explanation of the answer. You
can find the answers to all of the poll questions,
as well as worked calculations for the poll
questions, in the Course Resources section
of Blackboard. In this question, you should
pick the term that means “a tentative explanation
for observations.” Is it A: experimental
observations, B: hypothesis, C: law, or D:
theory?
The correct answer is B: hypothesis. It is
tentative, meaning we are unsure; it is a
guess. It answers the question “why” so
it is an explanation.
