>> host: Welcome back to
"Chemistry Matters."
Have you and your partner
settled on your top three
questions for investigating
the Ogeechee River fish kill?
Let's go back to our classroom
to see how your questions
compare to those of
some other students
who came up with questions
of their own.
>> teacher: Okay, let's hear
some of the ideas
you and your partner
came up with. Logan.
>> student: Okay.
Our top three questions are:
Did the fish die because of
a chemical pollution?
Did the fish die
due to excessive heat?
And, was there a drought
that prevented the animals
from getting enough water?
>> teacher: Good job.
How about back there?
>> student: We also had
the same question
about chemical pollution.
And we also came up
with these two:
Did the fish have some kind
of disease that killed them?
And, was there a predatory
invader that killed the fish?
>> student: But to be honest,
we don't know if
the second option
is as likely
since so many fish were killed
in such a small area.
>> teacher: Good job.
That's well thought out.
For now we want to ask
all the questions we can.
So it's good to put down
anything you think
could be a possibility.
And now I can give you
a bit more information, too.
In 2011, the King Finishing
Company was located
near the area of the fish kill.
They manufactured
flame-retardant textiles
and used a lot of chemicals
on their products
to reduce flammability.
Now with all of that in mind,
what do you all think
is the most likely cause
of the fish kill?
>> student: Maybe it was
because of some kind
of chemical pollution?
>> teacher: Okay.
Of course the fact
that we're standing
in a chemistry classroom
was probably
a pretty big hint, too.
In any case,
for the second part of
our science practice,
we need to formally define
the problem.
And the more concise
and specific, the better.
What do you think?
Go ahead, Keisha.
>> student: Mmm... How about,
"In May of 2011, many fish died
"on the Ogeechee River
"as a result of
"a chemical spill."
>> teacher: Great! Nice work!
>> host: Now that we've asked
a lot of questions
and clearly defined
the problem,
it's time to move on to
our second Science
and Engineering Practice,
"Generating a Hypothesis
"and Developing a Model."
In science, a hypothesis
refers to a testable idea.
A statement that's not
testable would not be science.
Science can only be used
on testable hypotheses.
A hypothesis is a tentative
explanation that can lead
to a prediction.
And a hypothesis
can be tested
by further investigation.
Unlike our questions
from the first science practice,
it should be in the form
of a statement.
Of course not every
investigation requires
a hypothesis.
In fact, over time
a lot of scientific discoveries
have come out of investigations
into the unknown,
so formal hypotheses
could not be formed.
But we'll develop one here
because we have some reliable
background information.
A good hypothesis
does three things
for the scientist.
First, it attempts to explain
an observation.
An observation
is any information gathered
using any of your five senses
and sometimes with the help
of lab instruments.
As we already said,
a good hypothesis
must be testable.
This testing can be performed
in many ways, in or outside
of a laboratory setting.
Finally, a good hypothesis
will predict the outcome
of an experiment.
Hypotheses are often rejected
when the outcome
of an experiment is different
from what it predicts.
But that's okay,
because scientists can
learn something from the test
no matter what the results are.
After a hypothesis is formed,
the next step is usually
developing a model to test it.
In science, a model
is a physical, conceptual,
or mathematical representation
of a real phenomenon
whose purpose is to explain
and predict what happens
in real life.
So models are basically
reasoning tools.
And they're usually
more complex than hypotheses.
The word model can mean
a lot of things.
There can be
physical models.
Or a model could be
a computer simulation,
or even an equation.
Sometimes, a model of
an airplane or car can be built,
showing how the vehicle
might look or move--
in smaller scale, of course.
A model home might be
a full size house
that people can walk through
to see what other houses
in a new neighborhood
might look like.
A fashion model might wear
designer clothing,
so that people can see
what the clothes look like.
So let's get back
to the classroom,
where students
are developing a hypothesis,
which will lead us
to a model for testing.
>> teacher: You all said
you think a chemical
is the most likely cause
of this fish kill.
What are some of the ways
a chemical could have gotten
into the river? Sam.
>> student: I think the
Finishing Company
could've spilled some kind
of acid into the water.
>> student: Or, it could've
been a fertilizer
from a nearby farm.
My uncle's a farmer
and he says that fertilizers
are bases.
>> student: Acid rain
is a possibility.
>> teacher: Good.
Anything else? Keisha.
>> student: Mmm... Maybe
the fish died
because water evaporated
and the chemicals
in the water, like an acid,
became more concentrated?
>> teacher: Okay.
All of these are testable ideas,
because we can check the river
to see if there's an acid
or a base in the water.
Then, we could even
examine the fish
to see if there's any acid
or base damage to their bodies.
So let's get started
on developing our hypothesis.
>> host: And this is
a good place to once again
take a break from our video
so you can do a little more
of the science practice
of developing a hypothesis.
Remember that in science
practice number one,
you asked questions.
But a hypothesis has to be
in the form of a statement.
First work alone
and write down the hypothesis
you would like to test
to learn what might've
happened to the fish.
Then discuss it
with a partner to create
the best hypothesis
possible.
When you're done,
we'll see you at the top
of the next video.