>> host: Are you a master
equation balancer yet?
If not, keep practicing.
We're going to use
balanced equations a lot.
For now, let's look at
the example you worked on
from our last video.
This is my balanced
magnesium oxide equation.
There are 2 magnesium atoms
for each molecule of oxygen
that produces 2 molecules
of magnesium oxide.
To get the equation
balanced correctly,
you must have the formulas,
like MgO, written correctly,
which we learned when we studied
bonding in Unit 4.
You might be wondering
what that triangle is
over the arrow.
As you know, the arrow
points to the products.
When you see a triangle,
it's the Greek letter delta,
and it means that energy
is added for the reaction
to occur.
Let me show you what I mean.
Here I have a piece
of solid magnesium.
There's oxygen in the air,
but nothing's happening.
I have to add energy
and then...
The magnesium reacts
with the oxygen
to make this white substance,
the magnesium oxide.
Reactions with one product
are called synthesis reactions.
You might also hear them
called combination
or addition reactions.
Synthesis reactions
combine two or more reactants
to form one product.
Synthesis reactions
are used all the time
in various professions,
such as manufacturing,
research, and medicine.
So I spoke with
Doctor Eileen Kennedy
of the University of Georgia's
College of Pharmacy
about how chemical reactions
and synthesis reactions
are important in her job.
Dr. Kennedy, thank you
so much for joining us today.
We're happy to have you here.
>> Dr. Kennedy: Thanks so much
for having me.
>> host: Now you are at
the College of Pharmacy
at the University of Georgia.
Tell us a little about
what you do there.
>> Dr. Kennedy: So, I spend
about half my time teaching,
so I will teach different
levels of courses, where
we generally teach Chemistry,
so pharmacy students,
so students that are ultimately
gonna be the pharmacist
in your lab, we teach them about
drug, you know, classes.
What targets we're going after,
how these compounds
were first developed.
What's better compounds now.
And we also work with, uh,
PhD students, and so these are
people that will ultimately
want to go into research
as a career, and these students
are interested in, you know,
how do we design a compound?
How do you identify a target?
All basic questions.
And so we're trying to make
those first steps of, you know,
leading towards how we can
develop an inhibitor.
>> host: So the other part
of what you do is research.
>> Dr. Kennedy: Yes, and so,
we have a research program
where we're largely focused
on synthesizing
inhibitor compounds.
So we pick disease targets
where we really lack effective
inhibitors for, you know,
for instance, cancer's a big
field, where there's a lot of
areas where we just don't have
good compounds for.
So how can we rethink
these problems?
Um, you know, if we know
that the target's important,
but we just don't have
any compounds that can hit it,
how can we design these sorts
of molecules or scaffolds
that can bind to
that particular target
and modulate its activity,
and then, potentially,
can outwork as an inhibitor,
so we have to ask all those
questions, design the compound,
and ultimately test it
and see if it does
what we think it does.
>> host: So you're talking about
the different steps
of the process, and how
each of those steps is really
a chemical reaction.
>> Dr. Kennedy: That's right.
>> host: We've covered several
reactions in this unit.
We've discussed decomposition,
single and double displacements,
synthetic reactions.
What types of reactions
do you see usually
in your lab?
>> Dr. Kennedy: So we do
organic transformations,
which is a really large
encompassing notion,
where there's maybe a few
hundred reactions that we can do
for organic reactions.
There's all sorts of different
things, so if we have that
end product, and we need
to step backwards,
we'll have multiple steps
where each of these
will involve some particular
type of reaction.
Sometimes as we go through that,
we find that one reaction
doesn't yield a good
amount of product,
and so that might not be
the best route that we took.
And so there are other ways
that we can retroactively
design a synthetic pathway.
So you sort of have to think
creatively from a end product.
You know, a lot of times,
there's, you know,
a hundred ways to get to
that same product.
You might have to go through
several of these
different routes
before you find a route
that ultimately leads to,
you know, a reasonable yield
of your end product.
>> host: So they're really
all synthetic reactions.
They're just targeted
at each step of the way,
based on what you
need to produce.
>> Dr. Kennedy: Yes. Yes,
and it'll be [indistinct],
so it can take a very long time
to finally get that compound,
but ultimately, you know,
the idea is once you get
that thing, it might end up
being a very active compound.
>> host: And looking
to the future,
what are your next steps?
What do you hope to see
coming out of your lab soon?
>> Dr. Kennedy: So there's
a variety of different diseases
where we just don't have
any good inhibitors
or modulators for these
particular targets,
so you know we're interested in
a lot of these different things.
There's a lot of different types
of cancers we're interested in,
so can we kind of expand
and try on that?
So we're going in several
different directions at once,
and just seeing if we have
more activity in one field
or another.
>> host: That is
really exciting.
And you involve students
at every step of the process.
Is that correct?
>> Dr. Kennedy: That's right.
So all of this work
is essentially done by students.
I'm sort of helping guide them,
but it's, you know,
their projects.
And so we have, um,
PhD students, and so these are
people who ultimately
want to have a research track,
and, uh, they're very
interested in, you know,
designing these inhibitors.
So they'll a lot of times,
lead these projects.
We also have PharmD students,
and so these are students
that are ultimately
gonna become pharmacists.
And a lot of them
are actually interested in
the drug development aspect,
too, and so they're interested
in, you know, wanting to see
how we design an inhibitor.
So they'll come
and do research in the lab.
We also have undergraduates
that are kind of deciding
whether they wanna perhaps
pursue science, or, you know,
a medical degree,
or something like that.
So they can come in the lab
and get experience
and see if this is something
that they really like.
And we also have a special
program in the summer
for, uh, high school students
called the Young Dawgs Program.
And so these students now get
an opportunity for six weeks
where they can come into
the lab, and sort of just see
what lab life is like.
What we do, you know, and our
day to day functions in a lab.
>> host: Wow. That's great.
So our students sitting
in chemistry right now
could be working with you
this summer.
>> Dr. Kennedy: That's right.
>> host: And, of course
there are many great benefits
to being a part
of this-this research.
Uh, but what are some other
benefits that the students
can get from working with you?
>> Dr. Kennedy: So, some
neat things that are available
to students, they can apply
for fellowships, and so
you can get money to work on
a particular kind of project.
And this can range from
government funding,
it can also be private funding.
Um, there's fellowships
to travel abroad,
so that you can do some kind
of research project
in another country.
So you get the cultural
experience, in addition to
the science experience.
There's a variety of different
sorts of things like that.
There's also a lot of meetings
where students can win awards,
or they get to present in front
of hundreds of scientists.
You know, so it's sort of
neat for them.
As they're beginning to,
you know, initiate their career
that they get to, you know,
speak as an authority
to, you know, Nobel Laureates
and things like that
in the audience.
>> host: Oh, this probably
opens a lot of doors for people.
>> Dr. Kennedy: Yeah, so--
>> host: That's exciting.
>> Dr. Kennedy: Yeah.
>> host: And speaking of that,
how did you get here?
What's your background
that landed you
where you are now?
>> Dr. Kennedy: So when I was
a high school student,
I was really interested
in science and felt that
I wanted to get
a medical degree.
So I was interested in being
a doctor, it seemed interesting.
But as I got into college,
and started my Premed degree,
um, I started taking a lot of
both biology and chemistry
classes, and I was a biology
major, but I found that I just
didn't like biology so much,
and I really, really enjoyed
chemistry, and as I went into
more advanced chemistry classes,
I just kept liking it more
and more. I liked the organic
lab class.
It just seemed my passion.
And ultimately, I decided to get
the PhD in chemistry
and pursue that further.
>> host: So those
chemistry classes
that started out as
just another requirement
for you, ended up completely
changing your career path.
>> Dr. Kennedy: Yeah, I just
found your niche, you spend
much time I think working
on things and I think to be
successful, you really have to
love what you do
and spend the time doing it.
So it's important to find
whatever that passion is
and pursue it, but yes,
it wasn't my intention.
>> host: And, what is
your passion?
What is your favorite part
of what you do now?
>> Dr. Kennedy: I really like
working with students.
I think it's fun to watch
a student where they
first come in the lab,
and still, you know, are
pretty unsure of themselves,
and a few years later,
can just come out as
a really amazing scientist
that can act as a world's
authority on whatever topic
they've studied.
And I just think that's
such a neat transformation
to see as they grow up,
and, you know, ultimately,
become a large contributor
I think to the
scientific community.
>> host: Great. Well, thank you
so much for joining us,
and for sharing your work
with us-- it's very exciting.
>> Dr. Kennedy: Thanks.
Thanks for having me.
>> host: Wow.
Synthesis reactions
right there at work.
Of course, synthesis
isn't the only type
of chemical reaction.
So let's head to
our classroom, to learn more.
>> professor: As you see here,
I've got two test tubes
full of water,
we have a cup of water,
a battery,
two metal thumbtacks and salt.
Now I'm gonna start off
by sprinkling some salt
into the water,
and that will allow
electricity to be conducted.
And I've already pushed
the two thumbtacks
through the bottom of the cup
and I've inverted
the two test tubes,
and I have them full of water.
Now what I'll do is
I'll place the battery
under the cup and make sure
that it touches the two
thumbtacks.
Now electricity can flow
through the water.
So tell me, what do you observe?
>> student: Hmm...
I see bubbles forming
on the tacks!
>> professor: Exactly.
Now let's give it a few minutes
and we'll come back and
make some more observations.
>> professor: Okay, it's been
about five minutes.
Tell me what else you observe.
>> student: Some water
came out of the test tubes.
You can see the levels
are lower.
>> student: And one test tube
lost almost twice as much water
as the other one.
>> professor: Good.
So what do you think
is happening?
>> student: Since the water
level is decreasing,
and there were bubbles,
I think the water's
breaking apart into gases.
>> professor: Okay, can you be
a little more specific? Anyone?
>> student: Don't the gases
have to be hydrogen
and oxygen, since those
are what water is made of?
>> student: Yeah,
the positive side
of the battery must be
collecting the negative
oxygen ions.
>> professor: Good. What else?
>> student: Well then,
the negative side of the battery
must be collecting
the positively charged
hydrogen ions.
>> professor: Great job
putting this together.
The bubbles are full of gas
because the water
is breaking apart
into positive hydrogen ions
and negative oxygen ions.
But we really didn't address
Kat's observation.
Why is there twice as much
of one gas?
>> student: Well, for each
water molecule there are
2 hydrogen atoms
and only 1 oxygen atom.
>> student: Yeah, and I remember
the balanced equation
for forming water
has 2 molecules of hydrogen
for every 1 molecule of oxygen.
>> student: So did we just
do the opposite
of making water?
>> professor: We sure did.
And you're right!
You saw twice as much
of one gas because the ratio
of hydrogen and oxygen
found in water is two to one.
That ratio is also represented
in the balanced equation
that you can see right here.
Now, any idea what this type
of reaction would be called?
>> student: A break down
reaction?
>> student: An anti-synthesis
reaction?
>> professor: Okay, you guys
have the right idea,
but actually chemists
call this type of reaction
a decomposition reaction
because you have one reactant
that's decomposing
or breaking apart
to form two or more products.
>> student: Like
a decomposing body?
>> professor: Something
like that, although
there are a lot more types
of reactions happening
when a body decomposes.
>> host: Okay, so decomposing
isn't the most pleasant visual.
But chemists do use
decomposition reactions
all the time.
So why would chemists
want to break things apart?
We can use electrolytic
decomposition reactions
to extract metals from their
naturally occurring compounds.
Typically chlorides and oxides.
If a chemist needed to obtain
pure sodium, they would not
be able to find it
just lying around.
Elemental sodium is far
too reactive to be found
naturally occurring in nature.
But we can take molten
sodium chloride, and with
a high voltage electrical
power supply, which we can
think of as an electron pump,
we can force the electrons
away from the chloride ions,
making elemental chlorine gas
at one electrode.
And the electrons are driven
toward the other electrode,
where sodium ions are converted
to elemental sodium.
The balanced chemical equation
representing this process is
two NaCl's are broken down
to for two Na's plus one Cl2.
Electrolytic decomposition
or electrolysis reactions
use a battery to force electrons
to be lost from one substance
and to be gained by another.
We can also use electrical
current to preferentially
plate out metals
onto certain substances.
We use electroplating
to bind protective
and beautiful metal surfaces
on jewelry, automobiles
and tools.
Of course there are many
electron transfer reactions
that do not require
an external power supply
in order to proceed.
They just occur spontaneously,
provided there's a pathway
for the electrons to travel.
To see exactly what I mean,
let's get back to our classroom.
>> professor: So each team has
a piece of copper
and a test tube
of distilled water.
Now if I asked you to place
the copper into the test tube,
what do you think would happen?
>> student: Nothing, right?
We've talked about this
in our discussion about
elements back in Unit 3.
It's like throwing pennies
in a fountain.
>> professor: Okay, well
let's test your hypothesis.
Place the copper
into the test tube.
>> student: See? Nothing.
>> professor: Okay.
Well now what I'll do is
use your scoopula
to take some solid
silver nitrate,
and I'm gonna place it
into this beaker
that contains distilled water.
Now when I stir it,
it's going to create
and aqueous solution of
silver nitrate.
Now what I would like you guys
to do is pour some of that
aqueous silver nitrate
into the test tube
and tell me what you observe.
>> student: What's happening
in there?
The copper looks sort of fuzzy.
>> student: Now the water's
getting bluish.
>> student: I see crystals
growing on the copper.
>> student: Obviously,
there's a chemical reaction
happening, but what's forming?
>> professor: Well think about
what you mixed together.
Copper and silver nitrate.
So based on your observations,
what's most likely forming
on the copper?
>> student: Well, it's grayish.
So, is it silver?
>> professor: That's a good
hypothesis. How did you
come up with that?
>> student: Well,
it's not copper
because it's the wrong color.
And nitrogen and oxygen
are gases, so that only
leaves silver.
>> student: Plus,
I know silver doesn't
dissolve in water,
or silver rings
would fall off
whenever we wash our hands.
>> professor: Great evidence
from both this lab,
and from your own life.
And you're right,
silver is forming.
So what is it that's causing
the solution to turn blue?
Any ideas? Well let's look
at the equation.
>> student: Since the solution
wasn't blue to start with,
a reactant isn't causing it
to be blue.
>> student: I know it's not
silver. Is it the copper?
>> student: Copper's not blue.
>> student: Well, solid copper
is a reactant.
The product part
is the copper 2+ ion,
which must be blue.
>> student: Why are we
ignoring the nitrate?
>> student: I ignored it
because it's the same
on both sides, so I think
it can't be causing the blue
since it's a reactant
and a product.
>> professor: You're doing
great-- The copper 2+ ion
does form a blue solution.
As you guys know from unit 3,
neutral copper must lose
2 electrons in order to become
the blue copper 2+ ion.
So where did those
electrons go?
Electrons from the copper metal
were transferred
to the silver 1+ ion
to make neutral silver
as well as the copper a 2+ ion.
And a reaction that transfers
electrons is known as
an oxidation reduction
or a redox reaction.
This particular type
of redox reaction is known
as a single displacement
or replacement reaction.
So that ion becomes neutral,
and in our reaction,
the copper becomes
positively charged
and the silver becomes
neutral.
So in this reaction,
the copper can replace
the positive silver ion,
but it cannot replace
the nitrate,
now because copper can form
the positive ion two.
But it just can't replace
any positive ion.
It can only replace
those that are less active.
And we'll cover this
in an upcoming lab.
>> host: So synthesis,
decomposition,
and single displacement
are 3 types of reactions,
but we're not done yet.
We still have two more to go.
The next reaction is known as
double displacement
or replacement.
Let's look at an example.
I have two clear solutions.
This one has potassium iodide,
K-I, in water
and this one is
lead (II) nitrate,
Pb(NO3)2, in water.
Let's mix them together.
Wow!
That is a bright yellow!
How did two clear solutions
make a yellow product?
Let's look at the reactants.
Remember, this is
a double displacement reaction,
so the potassium and lead
are going to trade
to form the new products.
Potassium separates from iodine
in water, and lead separates
from nitrate in water.
When they're mixed together,
the potassium will join
with the nitrate
while the lead joins
with the iodine.
Then the equation
must be balanced.
To balance the equation,
place a two in front of
KI and a two in front
of KNO3.
The solid lead (II) iodide
is the yellow solid
in our reaction.
You can see here
that the precipitate
is settling to the bottom.
Double displacement reactions
happen in a lot of places.
Even unlikely ones.
To show you what I mean,
I spoke with Dr. Mike Petelle
to tell us about
the effects of acid rain
on marble gravestones
and a whole lot more.
Thank you so much for
joining us, Dr. Petelle.
Now we just showed our students
some pictures of gravestones
that look old and worn,
and it's my understanding that
a lot of the wear and tear
on gravestones and on other
structures is caused by
acid rain, is that correct?
>> Dr. Petelle: That's right.
So those structures,
the gravestones and statues
that you've seen pictures of,
are made of, uh,
calcium carbonate.
>> host: Mm-hmm.
>> Dr. Petelle: And the sulfuric
acid that's found in acid rain
can react with that to create
calcium sulfate, which is
like gypsum that you find in
wall board, sheetrock,
you know, how friable and, uh,
how easily that breaks apart.
That can be washed away then.
It easily breaks down.
>> host: Oh. So you started
to talk about this, but what
exactly is acid rain?
>> Dr. Petelle: So, acid rain
or acid precipitation
because it can also occur
as acid snow, acid fog,
acid clouds, uh, acid sleet--
um, it is defined as...
So natural rainfall
is itself, acidic.
And the reason for that is that
carbon dioxide in the atmosphere
dissolves in the water
and the atmosphere
and it creates rain or clouds
with a pH of about 5.6.
So we define acid rain,
acid precipitation
as any rainfall
or precipitation that's below
5.6, so some-some cause
human activity for example
has made it more acidic
than normal.
>> host: Okay.
Now, how important a problem
these days is acid rain?
>> Dr. Petelle: Well the good
news is that in the U.S.
and in Europe, uh,
we've taken control measures
that have acid rain
becoming less of a problem.
So we've got a really good
animation that shows how
it's changed over the years.
And in about the last five
or ten years, you can see
pretty significant changes
in U.S. rainfall.
The average rainfall is a lot
less acidic than it was
in the past.
So, it's not as much of
a problem here.
Now, the effects of it
are lingering.
So, soils and lakes
and, uh, plants that have
been harmed have been harmed
and it'll take quite awhile
for those to recover.
Um, now in other parts
of the world, India and China,
particularly, we're seeing
a lot more acid rain,
acid precipitation.
>> host: Okay.
And, you've started to touch
on this a little bit,
but talk some more about
the problems that acid rain
can cause.
>> Dr. Petelle: Uh, so you see
problems in soil, in vegetation
and in aquatic systems.
Um, soils when they are
acidified by rainfall,
will lose nutrients.
They leach out.
So what happens is
the hydrogen ions
from the acid displace,
uh, cations in the soil.
Things like calcium,
uh, potassium, magnesium.
So they bump them off of
the negative sites that you find
in soil, and those then
wash out of the soil.
They're no longer available
as plant nutrients.
So you'll see declines
in plant nutrition, uh,
due to that activity.
The other thing is that, uh,
the acidity mobilizes aluminum.
That means that it causes
the aluminum to change form
so that it's soluble,
and now it can be, uh,
taken out by plants
and is poisonous to plants.
So it damages the roots
particularly, and again,
it makes the roots less able
to take up water and nutrients.
And, uh, plants like
legumes, which are nitrogen
fixers, uh, the bacteria
that help them with that process
are dis-- are damaged by the,
uh, aluminum as well.
Um, so you see root problems.
You see soil problems.
The above ground parts of
plants can be damaged directly
by the acidity in precipitation.
And so, uh, what can happen
is that the damage on the leaves
make it more susceptible
to infection by bacteria
and fungi.
It causes nutrients to
leach out it's leaves.
So the important nutrients
that are present in the leaves
wash out, they leach out.
Um, another problem that we see
is in aquatic systems, uh,
the acidity acidifies the lakes,
of course. And, uh, again,
aluminum becomes mobilized,
available in those lakes,
and the aluminum, uh,
attaches to the gills of fish,
and it can interfere
with their respiration.
And it also can interfere
with their osmotic balance.
They're less able to exchange,
uh, ions with the surrounding
environment, uh, their gills
do what our kidneys do.
And so they can't balance
their salt and water levels
as effectively. Um, so those
are some of the major problems
that we see.
>> host: So this is really
an even bigger problem
than we usually think of.
I'm hearing effects to
plant health, animal health
and then our own food sources.
>> Dr. Petelle: That's right.
Definitely, uh, fish supplies
in lakes have been drastically
impacted in the northeastern
United States for example.
And then, of course,
if the fish are impacted,
then they're gonna be rippling
food chain effects as well.
>> host: Right.
>> Dr. Petelle: So,
one interesting thing
that's happened is that,
um, the leaching problem
causes there to be lower levels
of calcium in the lakes,
and, uh, that's changing
the composition of
the microarthropods,
the-the small crustaceans
that are present in the lake
that the fish feed on,
and, uh, it selects for a type
of crustacean that has
a jelly covering,
and things don't like to
eat that as much.
It causes slime layers
on everything, so it, uh,
it can be an aesthetic
problem as well.
>> host: Right, wow.
The problem just goes
on and on, doesn't it?
>> Dr. Petelle: Definitely.
>> host: Now, what are
some of the causes
specifically in Georgia
of the acid precipitation
that we see here.
>> Dr. Petelle: Well, uh,
again, the, uh, acid rain
is caused by, uh, sulfates
that are released into the air
and nitrates that are released
into the air.
So, most of those sulfates
and nitrates come from
burning fossil fuels.
Um, and of those fossil fuels
coal is by far the worst problem
in terms of the sulfates.
So, uh, about 75% of the, uh,
sulfates that get into the air
in Georgia are due to
burning coal.
Um, in terms of nitrate,
about 60% comes from mobile
sources such as, uh,
automobiles burning fuel.
Uh, any high temperature,
uh, oxidation process
on our planet is gonna produce
nitrogen oxides because
there's a lot of nitrogen
in the atmosphere.
>> host: And you mentioned
some of the clean air
initiatives have already
started to lessen this problem.
>> Dr. Petelle: Yeah, so in
1990, the clean air act
was amended to start taking
care of the problem
with sulfates, uh, particularly
and to a lesser extent,
the nitrates that are released,
um, from burning fossil fuels.
So the utilities put in
scrubbers that are very
effective at removing sulfates.
And so that animation
that I mentioned shows
how much, uh, less of a problem
acid rain is becoming
due to the use of scrubbers
particularly, and there's
other things they can do.
They use different type of
combustion called
fluidized bed combustion.
And that reduces the nitrate,
uh, pollution as well.
So it sounds like a lot of,
a lot of things on that end
have been done to prevent
further acid rain.
But that also
we as individuals need to
focus on prevention as well.
>> Dr. Petelle: Yeah,
and so we as individuals,
the best thing we can do is
use less energy that comes from
fossil fuel sources.
Um, so if you use less energy
at home, if you drive less,
then that's gonna help
with the problem.
And, uh, the things that
we will be doing for
global climate change
remediation and, uh, prevention
will also help
because we'll be switching
to renewable sources
of energy that don't, uh,
produce the problem
that the fossil fuels do.
>> host: Great.
Very interesting.
Well, thank you so much
for joining us, Dr. Petelle.
>> Dr. Petelle: Thank you.
>> host: Now I understand
why old cemeteries look so...
well, old.
And I understand why
the reactions of acid rain
are so damaging
to our environment.
Let's look at one more
type of reaction--
a combustion reaction.
This burning candle
is giving off light and heat.
Burning coal to generate heat
for electric generators
and burning gasoline
to power cars
are both examples
of combustion reactions.
So with that in mind,
let's head back out
to our classroom.
>> professor: Combustion
reactions give off energy
in the form of heat
or light or both.
And I've already put
some ethyl alcohol
in this petri dish.
So let's see what happens
when I light it.
Now while that's burning,
let's take a look at
the reaction here
on the monitor.
And as you can see,
this is the balanced
equation and the C2H6O
that's the ethyl alcohol
that we just placed
in the petri dish.
What about the oxygen?
Where is that coming from?
>> student: Well,
there's oxygen in the air.
>> professor: Great.
What was the purpose
of the burning splint?
>> student: The splint was lit,
so it was giving off energy.
That energy is represented
by the Greek letter delta.
>> student: Did the energy
get the reaction started?
>> professor: Yes.
The burning splint provides
the energy necessary
to initiate the reaction.
In any combustion reaction,
carbon dioxide and water
are usually produced.
Of course alcohol
isn't the only thing
that will combust.
Now you might wonder how a fire
can produce water
without the water
putting the fire out.
But if you'll notice
in this case, so much energy
is given off throughout
the reaction that the water
produced is actually
in the gas phase.
And as you know,
hot gases move and spread
very quickly.
So the water in gas form
would not be able
to put out the fire.
>> host: Did you realize
that chemical reactions
are all around us?
And what we've covered so far
is only the tip of the iceberg--
which incidentally,
has chemical reactions
of its own!
Let's review the five types
of chemical reactions
we've learned about:
First, synthesis reactions,
reactions in which two
or more reactants produce
a single product.
And decomposition reactions,
where one reactant breaks into
two or more products.
This is the opposite
of synthesis.
single displacement reactions,
in which electrons
are transferred
so a neutral substance
can displace a charged one.
double displacement reactions,
or reactions in which
the like charged ions
of two ionic substances
trade places. And lastly,
combustion reactions,
where carbon and hydrogen
compounds react with oxygen
to produce carbon dioxide
and water.
Remember the reactions
you balanced
before this episode?
Now is a good time
to go back and review
the type of reaction
each equation represents.
And then you'll be ready
to move on to the next video
in our playlist that begins
to answer this question:
why do some substances
react with each other
while others don't?
See you then!