The law of conservation of mass - Todd Ramsey
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0:07 - 0:09Where does all this stuff come from?
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0:09 - 0:10This rock?
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0:10 - 0:11That cow?
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0:11 - 0:12Your heart?
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0:12 - 0:16Not the things themselves, mind you,
but what they're made of: -
0:16 - 0:19the atoms that are
the fabric of all things. -
0:19 - 0:23To answer that question, we look to
the law of conservation of mass. -
0:23 - 0:26This law says take an isolated system
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0:26 - 0:30defined by a boundary that matter
and energy cannot cross. -
0:30 - 0:34Inside this system, mass,
a.k.a. matter and energy, -
0:34 - 0:37can neither be created nor destroyed.
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0:37 - 0:40The universe, to the best
of our knowledge, -
0:40 - 0:42is an isolated system.
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0:42 - 0:46But before we get to that, let's look
at a much smaller and simpler one. -
0:46 - 0:49Here we have six carbon atoms,
12 hydrogen atoms, -
0:49 - 0:52and 18 oxygen atoms.
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0:52 - 0:56With a little energy,
our molecules can really get moving. -
0:56 - 0:59These atoms can bond together
to form familiar molecules. -
0:59 - 1:00Here's water,
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1:00 - 1:02and here's carbon dioxide.
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1:02 - 1:04We can't create or destroy mass.
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1:04 - 1:08We're stuck with what we've got,
so what can we do? -
1:08 - 1:10Ah, they have a mind of their own.
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1:10 - 1:14Let's see. They've formed more
carbon dioxide and water, six of each. -
1:14 - 1:19Add a little energy, and we can get them
to reshuffle themselves to a simple sugar, -
1:19 - 1:21and some oxygen gas.
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1:21 - 1:27Our atoms are all accounted for:
6 carbon, 12 hydrogen, and 18 oxygen. -
1:27 - 1:31The energy we applied is now stored
in the bonds between atoms. -
1:31 - 1:33We can rerelease that energy
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1:33 - 1:37by breaking that sugar back
into water and carbon dioxide, -
1:37 - 1:40and still, same atoms.
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1:40 - 1:44Let's put a few of our atoms aside
and try something a little more explosive. -
1:44 - 1:49This here is methane, most commonly
associated with cow flatulence, -
1:49 - 1:51but also used for rocket fuel.
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1:51 - 1:54If we add some oxygen
and a little bit of energy, -
1:54 - 1:56like you might get from a lit match,
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1:56 - 2:01it combusts into carbon dioxide,
water and even more energy. -
2:01 - 2:04Notice our methane started
with four hydrogen, -
2:04 - 2:09and at the end we still have four hydrogen
captured in two water molecules. -
2:09 - 2:14For a grand finale, here's propane,
another combustible gas. -
2:14 - 2:17We add oxygen, light it up,
and boom. -
2:17 - 2:19More water and carbon dioxide.
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2:19 - 2:21This time we get three CO2s
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2:21 - 2:24because the propane molecule
started with three carbon atoms, -
2:24 - 2:27and they have nowhere else to go.
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2:27 - 2:30There are many other reactions
we can model with this small set of atoms, -
2:30 - 2:34and the law of conservation of mass
always holds true. -
2:34 - 2:37Whatever matter and energy
go into a chemical reaction -
2:37 - 2:40are present and accounted
for when it's complete. -
2:40 - 2:43So if mass can't be created or destroyed,
-
2:43 - 2:46where did these atoms
come from in the first place? -
2:46 - 2:49Let's turn back the clock and see.
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2:49 - 2:54Further, further, further, too far.
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2:54 - 2:55Okay, there it is.
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2:55 - 2:56The Big Bang.
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2:56 - 3:00Our hydrogen formed from
a high-energy soup of particles -
3:00 - 3:04in the three minutes that followed
the birth of our universe. -
3:04 - 3:08Eventually, clusters of atoms accumulated
and formed stars. -
3:08 - 3:12Within these stars, nuclear reactions
fused light elements, -
3:12 - 3:14such as hydrogen and helium,
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3:14 - 3:18to form heavier elements,
such as carbon and oxygen. -
3:18 - 3:21At first glance, these reactions
may look like they're breaking the law -
3:21 - 3:24because they release
an astounding amount of energy, -
3:24 - 3:26seemingly out of nowhere.
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3:26 - 3:29However, thanks to
Einstein's famous equation, -
3:29 - 3:32we know that energy is equivalent to mass.
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3:32 - 3:35It turns out that the total mass
of the starting atoms -
3:35 - 3:39is very slightly more
than the mass of the products, -
3:39 - 3:44and that loss of mass perfectly
corresponds to the gain in energy, -
3:44 - 3:50which radiates out from the star as light,
heat and energetic particles. -
3:50 - 3:52Eventually, this star went supernova
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3:52 - 3:55and scattered its elements across space.
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3:55 - 3:58Long story short, they found each other
and atoms from other supernovas, -
3:58 - 4:00formed the Earth,
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4:00 - 4:04and 4.6 billion years later
got scooped up to play their parts -
4:04 - 4:07in our little isolated system.
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4:07 - 4:12But they're not nearly as interesting as
the atoms that came together to form you, -
4:12 - 4:13or that cow,
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4:13 - 4:14or this rock.
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4:14 - 4:17And that is why,
as Carl Sagan famously told us, -
4:17 - 4:20we are all made of star stuff.
- Title:
- The law of conservation of mass - Todd Ramsey
- Description:
-
View full lesson: http://ed.ted.com/lessons/the-law-of-conservation-of-mass-todd-ramsey
Everything in our universe has mass — from the smallest atom to the largest star. But the amount of mass has remained constant throughout existence even during the birth and death of stars, planets and you. How can the universe grow while maintaining its mass? Todd Ramsey answers that question by unravelling the law of conservation of mass.
Lesson by Todd Ramsey, animation by Vegso/Banyai.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 04:37
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Jennifer Cody edited English subtitles for The law of conservation of mass - Todd Ramsey |
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