WEBVTT

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[upbeat music]

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- ICE IS SOMETHING
WE'VE ALL SEEN,

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WHETHER IT'S ICE ON A LAKE
OR ICE IN YOUR GLASS.

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ALL ICE SHARES
SOME SPECIAL PROPERTIES,

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BUT JUST WHAT ARE
THOSE PROPERTIES

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AND WHAT MAKES ICE SO DIFFERENT
FROM OTHER SOLIDS?

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TO FIND OUT, LET'S TURN
TO SOME PEOPLE AT NASA

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WHO HAVE MADE A CAREER
OUT OF STUDYING ICE.

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- WELL, FUNDAMENTALLY,

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YOU PROBABLY ALREADY KNOW
WHAT ICE IS.

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IT'S THAT ICE CUBE
THAT'S IN YOUR FREEZER

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OR IN YOUR COLD DRINK.

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ICE, AT ITS MOST FUNDAMENTAL,
IS FROZEN WATER.

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- WHEN WATER HITS
A CERTAIN TEMPERATURE,

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WHICH IS 32 DEGREES FAHRENHEIT
OR 0 DEGREES CELSIUS,

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IT FREEZES.

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AND HERE WE HAVE AN EXAMPLE
OF THIS.

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HERE IS ICE.

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THIS ICE WAS LIQUID WATER
NOT TOO LONG AGO,

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AND IT JUST--IT REACHED
A CERTAIN TEMPERATURE,

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AND IT EXPANDED AND IT FROZE
INTO THIS SOLID BLOCK.

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- ICE IS IMPORTANT TO OUR WORLD,

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BECAUSE IT'S ONE
OF THE MAIN PARTS OF THE PLANET

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THAT CONTROLS OUR CLIMATE,

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HOW WARM OR HOW COOL IT IS.

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IN THE POLAR AREAS--

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SO CLOSE TO THE NORTH POLE,
CLOSE TO THE SOUTH POLE--

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IT'S COLD YEAR-ROUND,
AND WE FIND A LOT OF ICE THERE.

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AND THAT ICE AFFECTS
WHAT OUR WEATHER IS LIKE

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HERE IN THE UNITED STATES.

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- WHEN MOST SOLIDS ARE HEATED,

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THEY MELT INTO LIQUIDS.

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WHEN A LIQUID COOLS DOWN,

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IT FREEZES INTO A SOLID.

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BUT WATER IS SPECIAL,

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BECAUSE SOMETHING
VERY DIFFERENT HAPPENS

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WHEN IT BECOMES A SOLID.

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- ICE IS A REALLY UNIQUE SOLID.

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A LOT OF OTHER LIQUIDS
AS THEY FREEZE AND FORM A SOLID,

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THAT SOLID IS HEAVIER
AND IT'S DENSE,

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AND IT SINKS DOWN TO THE BOTTOM
OF THE LIQUID.

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BUT AS YOU KNOW, YOUR ICE CUBE
FLOATS IN A GLASS OF WATER,

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SO WHEN YOU FREEZE WATER
TO MAKE ICE,

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IT'S ACTUALLY LESS DENSE
THAN THE WATER,

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AND SO IT FLOATS RIGHT UP
ON THE TOP.

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- HERE WE HAVE A GLASS
OF WATER,

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JUST REGULAR,
ROOM-TEMPERATURE WATER.

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AND WE TAKE ICE, WHICH IS,
YOU KNOW, 32 DEGREES OR BELOW,

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AND IF WE DROP A COUPLE
ICE CUBES IN THIS WATER,

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WE SEE THAT
IT DEFINITELY FLOATS.

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WE'LL SEE THAT
IT IS DEFINITELY LESS DENSE

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THAN THE LIQUID WATER.

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- BUT FLOATING ICE
IS REALLY IMPORTANT

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FOR LIFE ON EARTH TOO.

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IF FROZEN WATER DID NOT FLOAT,

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IT WOULD SINK TO THE BOTTOM
OF A LAKE OR A POND

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OR EVEN THE OCEAN.

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THE SUMMER SUN WOULD MELT
SOME OF THE ICE,

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BUT NOT ALL OF IT.

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EVERY YEAR, MORE ICE WOULD SINK
TO THE BOTTOM

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UNTIL THE LAKES AND THE RIVERS
FILLED WITH ICE

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AND BECOME SOLID.

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BUT ICE FLOATS
IN LIQUID WATER,

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SO OUR LAKES AND OCEANS
DON'T FREEZE

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FROM THE BOTTOM UP.

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EVEN IN COLD WEATHER,

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LIVING THINGS CAN STILL LIVE
IN THE LIQUID WATER

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THAT IS UNDER THE ICE.

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WATER, BOTH LIQUID AND SOLID,
MAKES OUR WORLD

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A SPECIAL PLACE TO LIVE.