WEBVTT

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[MUSIC PLAYING]

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JESSICA HARROP: Hi,
I'm Jessica and I'm

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going to be talking about
a chemical demonstration

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today that I like to call
"Death of a Gummy Bear."

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We eat these little
guys all the time

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and our bodies
break down the sugar

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in a series of
chemical reactions.

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But what happens when you break
down the sugar in a gummy bear

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outside of our bodies?

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Well, MIT'S Dr. John
Dolhun is going to show us.

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Here he is at the Cambridge
Science Festival at MIT.

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JOHN DOLHUN: Now I'm
going to actually

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be combusting a gummy candy.

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And my wife said, please
don't tell them it's a bear.

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Guess what?

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It's a bear.

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And I'm going to
eat one right now.

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And I'm eating a gummy candy.

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It's sugar.

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And I'm going to chew on it, and
eat it, and what do you think's

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going to happen to it?

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AUDIENCE: It's
going to break down.

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JOHN DOLHUN: It's going to
break down into carbon dioxide.

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Tomorrow I'm going to
be breathing out CO2.

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I'm going to be perspiring.

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Water is going to be coming out.

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And I'm going to
make a lot of energy,

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and I'm going to take that
energy and store it up as ATP,

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and it's going to help me clean
all these dishes tomorrow.

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I don't want to think
about that but I'm

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going to need the energy.

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And now I'm going to
do this same reaction

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inside of a test tube.

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And I want you to compare
what you just saw.

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You didn't see a lot
of smoke and fire

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coming out of my mouth, did you?

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Not yet, OK.

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So Clifton, you can.

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Clifton's going to play
a little rondo or music

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while I set this reaction up.

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[MUSIC PLAYING]

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JESSICA HARROP: So what
is Dr. Dolhun doing?

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First, he put some solid
potassium chlorate in a test

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tube and heated it up.

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The heat causes the solid
to melt and become a liquid.

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So this little
triangle means heat.

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It turned from a
solid to a liquid.

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As it's being heated, the liquid
potassium chlorate immediately

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starts breaking down into two
products, potassium chloride

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and oxygen. Now potassium
chloride is a solid

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and the oxygen is a gas.

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Looks like this.

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Now let's see what happens when
Dr. Dolhun adds the gummy bear.

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[MUSIC PLAYING]

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So let's break down
what just happened.

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The sugar from the
gummy bear and oxygen

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reacted to produce
carbon dioxide and water,

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releasing a lot of
energy as heat and light.

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This is what that
looks like, and I'm

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going to draw sucrose,
or sugar, in red

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because it's from
the gummy bear.

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This reaction is
probably familiar to you.

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It's a combustion
reaction, which

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is when a fuel reacts with
oxygen to produce carbon

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dioxide and water and at
the same time, releasing

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a bunch of energy.

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So why is so much
energy released

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and where does it come from?

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To show you, I'm going
to draw the structures.

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Now, if you're unfamiliar with
organic chemistry notation,

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each of the lines between the
elements that I'm going to draw

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represents a
covalent bond, which

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is the sharing of two
electrons between two atoms.

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So let me draw those.

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So here are the reactants
and here are the products.

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Now by looking at the number
of bonds and the type of bonds,

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so a carbon bonded to an
oxygen, or a carbon bonded

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to a carbon, and a single
bond versus a double bond,

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you can calculate
the energy difference

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between the left side of
the reaction, the reactants,

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and the right side,
or the products.

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Now all combustion
reactions have more energy

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stored in the reactants
than the products,

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so as the reaction progresses,
this energy has to go somewhere

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and it's released
as heat and light.

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Now the amount of energy
released from this explosion

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is exactly the same as
the amount of energy

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that would be
released in my body

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when I eat this gummy bear.

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The difference is that
proteins in my body

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are set up in pathways
that extract the energy

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in small, manageable bundles.

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So I power my
everyday activities

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like dancing and running,
but I don't explode.

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Evolution has trained
biological systems

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to efficiently extract
energy from our environment.

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That's it for me today.

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I'll see you next time.

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[MUSIC PLAYING]

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