Donald Johnson, Age 12, Of Lansing, Mich.,, for his question:
How cold is cold?
On a frosty morning in Michigan, the temperature may drop several degrees below zero. Brr; this.. You might think, is as cold as cold can get. But compared to most spots in the universe, that chilly morning is warm. In the vast reaches of outer space, a chilly morning on earth might seem as hot as a blast furnace does to us.
The seething heart of our sun is estimated to be about 10.,000 times hotter than a blast furnace and many stars are hotter still. There seems no limit to how hot an object can gets and the temperature of the stars soars up to millions of degrees. A cooler object has less heat energy than a warmer object, and cold is merely absence of heat.
Solids, liquids and gases can be hot or warm, cool or cold, and they behave differently under different temperatures, At 0 degrees centigrade, water freezes to solid ice. At 100 degrees, it boils and becomes a gaseous vapor. These and other changes caused by temperature occur because solids, liquids and gases are made from atoms and molecules.
Heat is a form of energy which the atoms and molecules use to get up speed. The molecules in a solid poker have enough energy to shiver and vibrate. The molecules in a liquid have enough energy to flow along linked together somewhat like a game of follow the leader. Gas molecules have enough energy to separate and zoom around, crashing into each other at terrific speeds and all this speeding energy comes from heat. The hotter a substance becomes, the faster its atoms and molecules move.
As a substance loses heat, its molecules lose speed energy. They move more and more slowly. As the temperature drops, the molecules of a gas slow down and form a liquid. As still more heat energy is lost, the molecules crawl to a stop and the substance becomes a solid. But there is still some heat left in ordinary ice and even in dry ice, which is so cold that you get frost bitten from touching it.
There is a pointy however, at which a substance loses all absolutely all of its heat. This colder than cold temperature is called absolute zero. On the fahrenheit temperature scale,, absolute zero is minus 459.8 degrees. On the centigrade scale, absolute zero is 273.2 degrees. This is as cold as anything can possibly get ¬or as cold as cold can get.
Most scientists use the centigrade temperature scale on which the freezing point of water is zero degrees and its boiling point is 100 degrees. For measuring lower¬than low temperatures., scientists use the absolute scales on which zero is absolute zero. On the absolute temperature scale, there are no minus degrees below zero .for a substance with any heat at all is warmer than absolute zero.