الصفر المطلق

ﺍﻟﺼﻔﺮ ﺍﻟﻤﻄﻠﻖ * ﻫﻲ ﺩﺭﺟﺔ ﺍﻟﺤﺮﺍﺭﺓ
ﺍﻟﺘﻲ ﻳﻨﻌﺪﻡ ﻋﻨﺪﻫﺎ ﺿﻐﻂﺍﻟﻐﺎﺯ ﺍﻟﻤﺜﺎﻟﻲ
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. ﻭﺗﻌﻨﻲ ﺍﻟﺤﺎﻟﺔ ﺍﻟﺘﻲ ﺗﻜﻮﻥ ﺩﺭﺟﺔ ﺣﺮﺍﺭﺓ ﺍﻟﻤﺎﺩﺓ ﻓﻴﻬﺎ ﺃﻗﻞ ﻣﺎ ﻳﻤﻜﻦ ﺃﻥ ﺗﺼﻞ ﺇﻟﻴﻪ ﺇﻃﻼﻗﺎ . ﻭﺗﻘﻀﻲ ﺑﺄﻥ ﺟﻤﻴﻊ ﺫﺭﺍﺕ
ﺃﻭ ﺟﺰﻳﺌﺎﺕ
ﺍﻟﻤﺎﺩﺓ ﺗﻜﻮﻥ ﻟﻬﺎ ﺃﻗﻞ ﻃﺎﻗﺔ
ﻓﻲ ﺗﻠﻚ ﺍﻟﺤﺎﻟﺔ .
ﺍﻛﺘﺸﻒ ﺍﻟﻌﻠﻤﺎﺀ ﺍﻥ ﺃﻗﻞ ﺩﺭﺟﺔ ﺣﺮﺍﺭﺓ ﻳﻤﻜﻦ ﺍﻟﻮﺻﻮﻝ ﺇﻟﻴﻬﺎ ﻫﻲ 273.15 ﺩﺭﺟﺔ ﺳﻴﻠﺰﻳﻮﺱ
ﺗﺤﺖ ﺍﻟﺼﻔﺮ . ﺗﻢ ﺍﻟﻮﺻﻮﻝ ﺇﻟﻰ ﻣﻌﺮﻓﺔ ﻫﺬﺍ ﺍﻟﻘﻴﺎﺱ ﺑﺎﻻﻋﺘﻤﺎﺩ ﻋﻠﻰ ﺍﻟﻌﻼﻗﺔ ﺍﻟﻄﺮﺩﻳﺔ
ﺑﻴﻦ ﺩﺭﺟﺔ ﺣﺮﺍﺭﺓ ﻏﺎﺯ ﻣﺎ ﻭﺿﻐﻄﻪ ﻭﺑﺎﻟﺘﺠﺮﺑﺔ ﺗﺒﻴﻦ ﺃﻥ ﺿﻐﻂ ﺍﻟﻐﺎﺯ ﻳﺴﺎﻭﻱ ﺻﻔﺮﺍ ﻋﻨﺪ ﺩﺭﺟﺔ ﺣﺮﺍﺭﺓ 273.15 ﺩﺭﺟﺔ ﺳﻴﻠﺰﻳﻮﺱ ﺗﺤﺖ ﺍﻟﺼﻔﺮ .
ﻳﺴﻤﻰ ﻣﻘﻴﺎﺱ ﺍﻟﺤﺮﺍﺭﺓ ﺍﻟﺬﻱ ﻟﻪ ﻗﻴﻤﺔ ﺻﻔﺮ ﻋﻨﺪ ﺩﺭﺟﺔ ﺍﻟﺼﻔﺮ ﺍﻟﻤﻄﻠﻖ ﺑﻤﻘﻴﺎﺱ ﺣﺮﺍﺭﺓ ﻣﻄﻠﻖ . ﻭﻫﻨﺎﻙ ﻣﻘﻴﺎﺱ ﻭﺍﺣﺪ ﻳﻄﺎﺑﻖ ﻫﺬﺍ ﺍﻟﻮﺻﻒ ﻭﻫﻮ ﻣﻘﻴﺎﺱ ﻛﻠﻔﻦ
. ﺍﻟﺮﻗﻢ ﺻﻔﺮ ﻋﻠﻰ ﻫﺬﺍ ﺍﻟﻤﻘﻴﺎﺱ ﻳﺴﺎﻭﻱ ﺍﻟﺼﻔﺮ ﺍﻟﻤﻄﻠﻖ ﺃﻭ ‏( 0 ﻛﻠﻔﻦ
‏) ﻭﻻ ﺗﺴﺘﻌﻤﻞ ﻛﻠﻤﺔ " ﺩﺭﺟﺔ " ﻟﻠﻘﻴﺎﺱ ﺑﻪ .
ﻣﻘﻴﺎﺱ ﻛﻠﻔﻦ
ﻣﺮﺗﺒﻂ ﺑﻤﻘﻴﺎﺱ ﺳﻴﻠﺰﻳﻮﺱ ﺣﻴﺚ ﺃﻥ ﻛﻞ ﻭﺍﺣﺪ ﺩﺭﺟﺔ ﺳﻴﻠﺰﻳﻮﺱ ﺗﺴﺎﻭﻱ ﻭﺍﺣﺪ ﻛﻠﻔﻦ
، ﻭﻟﻜﻦ ﺍﻟﻔﺮﻕ ﺃﻥ ﻛﻠﻔﻦ ﻳﺒﺪﺃ ﻋﻨﺪ ﺩﺭﺟﺎﺕ ﺍﻟﺤﺮﺍﺭﺓ ﻣﻦ - 273.15 ﺃﻣﺎ ﺳﻴﻠﺰﻳﻮﺱ ﻓﻴﺒﺪﺃ ﻣﻦ 0 .
ﻭﻫﻜﺬﺍ ﻳﻤﻜﻦ ﻣﻌﺮﻓﺔ ﺩﺭﺟﺔ ﺣﺮﺍﺭﺓ ﺳﻴﻠﺰﻳﻮﺱ ﻣﻦ ﻛﻠﻔﻦ ﺑﺘﻨﻘﻴﺺ 273.15 ﻣﻦ ﻛﻠﻔﻦ ﻭﺍﻟﻌﻜﺲ . ﻓﺎﺫﺍ ﺍﻓﺘﺮﺿﻨﺎ ﺃﻥ ﺩﺭﺟﺔ ﺣﺮﺍﺭﺓ ﻣﺎﺩﺓ ﺗﺒﻠﻎ 50 ﻛﻠﻔﻦ
ﻓﺎﻧﻬﺎ ﺗﺴﺎﻭﻱ ﺃﻳﻀﺎ -50 273.15 ، ﻓﻴﻜﻮﻥ ﺍﻟﻨﺎﺗﺞ - 223.15 ﺩﺭﺟﺔ ﺳﻴﻠﺰﻳﻮﺱ ‏( ﺃﻱ 223.15 ﺗﺤﺖ ﺍﻟﺼﻔﺮ ﺳﻠﺰﻳﻮﺱ ‏) .
ﺃﻱ ﺃﻥ : * T ‏( ﻛﻠﻔﻦ ‏) = t ‏( ﺩﺭﺟﺔ ﻣﺌﻮﻳﺔ ‏) + 273.16
ﻳﻌﺘﻘﺪ ﺍﻟﻔﻴﺰﻳﺎﺋﻴﻮﻥ ﺃﻥ ﺩﺭﺟﺔ ﺍﻟﺤﺮﺍﺭﺓ ﻻ ﻳﻤﻜﻦ ﺃﻥ ﺗﺼﻞ ﺇﻟﻰ ﺍﻟﺼﻔﺮ ﺍﻟﻤﻄﻠﻖ ﺗﻤﺎﻣﺎً، ﻭﺃﻗﻞ ﺩﺭﺟﺔ ﺣﺮﺍﺭﺓ ﺗﻢ ﺍﻟﻮﺻﻮﻝ ﺇﻟﻴﻬﺎ ﻫﻲ ﻭﺍﺣﺪ ﻓﻲ ﺍﻷﻟﻒ ﻣﻠﻴﻮﻥ ﻣﻦ ﺍﻟﺪﺭﺟﺔ ﻓﻮﻕ ﺍﻟﺼﻔﺮ ﺍﻟﻤﻄﻠﻖ . ﻭﻳﺤﺎﻭﻝ ﺍﻟﻌﻠﻤﺎﺀ ﺍﻵﻥ ﺇﺛﺒﺎﺕ ﻋﻤﻠﻴﺎً ﺍﻟﺼﻔﺮ ﺍﻟﻤﻄﻠﻖ ﻟﻠﻐﺎﺯ ﻭﺍﻟﺬﻱ ﻳﻨﻌﺪﻡ ﻋﻨﺪﺓ ﺿﻐﻂ ﺍﻟﻐﺎﺯ ﻭﺣﺠﻤﺔ ﻋﻠﻰ ﺗﺪﺭﺝ ﻛﻠﻔﻦ . .. ﻓﻲ ﺑﻌﺾ ﺍﻟﻤﺼﺎﺩﺭ ﺗﻌﺘﺒﺮ ﺩﺭﺟﺔ ﺍﻟﺼﻔﺮ ﺍﻟﻤﻄﻠﻖ ‏( - 273.16 ‏) ﺩﺭﺟﺔ .