[upbeat music]
- ICE IS SOMETHING WE'VE ALL SEEN,
WHETHER IT'S ICE ON A LAKE OR ICE IN YOUR GLASS.
ALL ICE SHARES SOME SPECIAL PROPERTIES,
BUT JUST WHAT ARE THOSE PROPERTIES
AND WHAT MAKES ICE SO DIFFERENT FROM OTHER SOLIDS?
TO FIND OUT, LET'S TURN TO SOME PEOPLE AT NASA
WHO HAVE MADE A CAREER OUT OF STUDYING ICE.
- WELL, FUNDAMENTALLY,
YOU PROBABLY ALREADY KNOW WHAT ICE IS.
IT'S THAT ICE CUBE THAT'S IN YOUR FREEZER
OR IN YOUR COLD DRINK.
ICE, AT ITS MOST FUNDAMENTAL, IS FROZEN WATER.
- WHEN WATER HITS A CERTAIN TEMPERATURE,
WHICH IS 32 DEGREES FAHRENHEIT OR 0 DEGREES CELSIUS,
IT FREEZES.
AND HERE WE HAVE AN EXAMPLE OF THIS.
HERE IS ICE.
THIS ICE WAS LIQUID WATER NOT TOO LONG AGO,
AND IT JUST--IT REACHED A CERTAIN TEMPERATURE,
AND IT EXPANDED AND IT FROZE INTO THIS SOLID BLOCK.
- ICE IS IMPORTANT TO OUR WORLD,
BECAUSE IT'S ONE OF THE MAIN PARTS OF THE PLANET
THAT CONTROLS OUR CLIMATE,
HOW WARM OR HOW COOL IT IS.
IN THE POLAR AREAS--
SO CLOSE TO THE NORTH POLE, CLOSE TO THE SOUTH POLE--
IT'S COLD YEAR-ROUND, AND WE FIND A LOT OF ICE THERE.
AND THAT ICE AFFECTS WHAT OUR WEATHER IS LIKE
HERE IN THE UNITED STATES.
- WHEN MOST SOLIDS ARE HEATED,
THEY MELT INTO LIQUIDS.
WHEN A LIQUID COOLS DOWN,
IT FREEZES INTO A SOLID.
BUT WATER IS SPECIAL,
BECAUSE SOMETHING VERY DIFFERENT HAPPENS
WHEN IT BECOMES A SOLID.
- ICE IS A REALLY UNIQUE SOLID.
A LOT OF OTHER LIQUIDS AS THEY FREEZE AND FORM A SOLID,
THAT SOLID IS HEAVIER AND IT'S DENSE,
AND IT SINKS DOWN TO THE BOTTOM OF THE LIQUID.
BUT AS YOU KNOW, YOUR ICE CUBE FLOATS IN A GLASS OF WATER,
SO WHEN YOU FREEZE WATER TO MAKE ICE,
IT'S ACTUALLY LESS DENSE THAN THE WATER,
AND SO IT FLOATS RIGHT UP ON THE TOP.
- HERE WE HAVE A GLASS OF WATER,
JUST REGULAR, ROOM-TEMPERATURE WATER.
AND WE TAKE ICE, WHICH IS, YOU KNOW, 32 DEGREES OR BELOW,
AND IF WE DROP A COUPLE ICE CUBES IN THIS WATER,
WE SEE THAT IT DEFINITELY FLOATS.
WE'LL SEE THAT IT IS DEFINITELY LESS DENSE
THAN THE LIQUID WATER.
- BUT FLOATING ICE IS REALLY IMPORTANT
FOR LIFE ON EARTH TOO.
IF FROZEN WATER DID NOT FLOAT,
IT WOULD SINK TO THE BOTTOM OF A LAKE OR A POND
OR EVEN THE OCEAN.
THE SUMMER SUN WOULD MELT SOME OF THE ICE,
BUT NOT ALL OF IT.
EVERY YEAR, MORE ICE WOULD SINK TO THE BOTTOM
UNTIL THE LAKES AND THE RIVERS FILLED WITH ICE
AND BECOME SOLID.
BUT ICE FLOATS IN LIQUID WATER,
SO OUR LAKES AND OCEANS DON'T FREEZE
FROM THE BOTTOM UP.
EVEN IN COLD WEATHER,
LIVING THINGS CAN STILL LIVE IN THE LIQUID WATER
THAT IS UNDER THE ICE.
WATER, BOTH LIQUID AND SOLID, MAKES OUR WORLD
A SPECIAL PLACE TO LIVE.