{"id":176,"date":"2017-09-17T17:27:31","date_gmt":"2017-09-17T17:27:31","guid":{"rendered":"http:\/\/80.85.86.254\/sjor\/?p=176"},"modified":"2024-03-28T18:39:53","modified_gmt":"2024-03-28T18:39:53","slug":"1-3-eiginleikar-vatns-og-sjavar","status":"publish","type":"post","link":"https:\/\/himinnoghaf.is\/mengunsjavar\/index.php\/2017\/09\/17\/1-3-eiginleikar-vatns-og-sjavar\/","title":{"rendered":"1.3 Eiginleikar vatns og sj\u00e1var"},"content":{"rendered":"<p>Vatn (H<sub>2<\/sub>O) er eina n\u00e1tt\u00farulega efni\u00f0 \u00e1 j\u00f6r\u00f0inni sem finnst \u00ed \u00f6llum \u00feremur f\u00f6sum: frosi\u00f0 (\u00eds), flj\u00f3tandi (vatn) og sem lofttegund (vatnsgufa). Vatn er nau\u00f0synlegt \u00f6llu l\u00edfi, eins og vi\u00f0 \u00feekkjum \u00fea\u00f0. Frumur eru a\u00f0 miklu leyti vatn, e\u00f0a um 70%. Vatn er <span class=\"tooltips \" style=\"\" title=\"Sameind sem hefur tilhneigingu til a\u00f0 klofna \u00ed j\u00f3nir e\u00f0a sameind sem hefur \u00f3jafna rafeindadreifingu \u00fe\u00f3tt h\u00fan n\u00e6gi ekki til j\u00f3nunar. \u00cd vatnssameind er \u00f3j\u00f6fn rafeindadreifing, s\u00farefnissameindirnar eru \u00f6rl\u00edti\u00f0 neikv\u00e6tt hla\u00f0nar en vetnissameindirnar \u00f6rl\u00edti\u00f0 j\u00e1kv\u00e6tt hla\u00f0nar.\">skautu\u00f0 sameind<\/span> og myndar svok\u00f6llu\u00f0 <span class=\"tooltips \" style=\"\" title=\"Vetnistengi eru allsterkir tv\u00edskautskraftar \u00e1 milli vetnissameindar \u00ed einni vatnssameind og s\u00farefnissameindar \u00ed annarri vatnssameind.\">vetnistengi<\/span>. Vatn hefur marga mikilv\u00e6ga eiginleika sem vi\u00f0 sko\u00f0um n\u00fa n\u00e1nar.<\/p>\n<h5><span class=\"arrow-pg\"><\/span><em><strong>Vatn er g\u00f3\u00f0ur leysir<\/strong><\/em><\/h5>\n<p>Vatn er skauta\u00f0 efni (vetnisj\u00f3nirnar eru pl\u00fashla\u00f0nar og s\u00farefnisj\u00f3nirnar m\u00ednushla\u00f0nar). M\u00f6rg efni leysast \u00fev\u00ed vel \u00ed vatni. Til d\u00e6mis leysast s\u00f6lt og n\u00e6ringarefni mj\u00f6g vel \u00ed vatni. Efnaskipti geta \u00e1tt s\u00e9r sta\u00f0 mun hra\u00f0ar \u00ed frumum en ella vegna \u00feess a\u00f0 efnin eru \u00e1 uppleystu formi \u00ed vatnslausn frumanna. \u00deannig geta l\u00edfverur brug\u00f0ist hra\u00f0ar vi\u00f0 umhverfisa\u00f0st\u00e6\u00f0um. Sj\u00f3rinn er einmitt vatn me\u00f0 uppleystum s\u00f6ltum og er me\u00f0alselta sj\u00e1var 35\u2030 (\u00fe.e. 35 kg af s\u00f6ltum \u00e1 hver 1000 kg af sj\u00f3). S\u00f6ltin hafa borist til sj\u00e1var vegna ve\u00f0runar \u00e1 bergi og uppleysingar eldgosagufa. Selta sj\u00e1var er breytileg fr\u00e1 einum sta\u00f0 til annars. Mismuninn m\u00e1 rekja til \u00fdmissa \u00fe\u00e1tta s.s. uppgufunar, \u00farkomu og ferskvatnsa\u00f0streymis. Uppgufun er mismikil og fer eftir hitastigi sj\u00e1var og vindum. \u00dear sem uppgufun er mikil er selta alla jafna h\u00e6rri. L\u00e6gra saltmagn er a\u00f0 finna \u00fear sem \u00e1r og \u00farkoma b\u00e6ta vi\u00f0 miklu ferskvatni. Atlantshafi\u00f0 er til a\u00f0 mynda saltara en Kyrrahafi\u00f0 \u00fear sem meiri \u00farkoma fellur \u00ed Kyrrahafi\u00f0. Br\u00e1\u00f0nun og myndun \u00edss hefur \u00e1hrif \u00e1 saltmagn heimskautasv\u00e6\u00f0a.<\/p>\n<div id=\"wpfp_122ea69450491668d747fc543b062a65\" data-item=\"{&quot;sources&quot;:[{&quot;src&quot;:&quot;https:\\\/\\\/himinnoghaf.is:443\\\/mengunsjavar\\\/wp-content\\\/uploads\\\/01-2-1-Myndband-1.2-SSS_960x540_30p.mp4&quot;,&quot;type&quot;:&quot;video\\\/mp4&quot;}],&quot;splash&quot;:&quot;https:\\\/\\\/himinnoghaf.is\\\/mengunsjavar\\\/wp-content\\\/uploads\\\/01-2-1-Title-Myndband1-2.png&quot;}\" class=\"flowplayer no-brand is-splash is-paused skin-slim no-svg fp-slim fp-edgy fixed-controls\" style=\"position:relative; max-width: 640px; max-height: 330px; \" data-ratio=\"0.5156\">\n\t<div class=\"fp-ratio\" style=\"padding-top: 51.56%\"><\/div>\n\t<img decoding=\"async\" class=\"fp-splash\" alt=\"video\" src=\"https:\/\/himinnoghaf.is\/mengunsjavar\/wp-content\/uploads\/01-2-1-Title-Myndband1-2.png\" style=\"position:absolute;top:0;width:100%\" \/>\n\t<div class=\"fp-ui\"><noscript>Please enable JavaScript<\/noscript><div class=\"fp-play fp-visible\"><svg class=\"fp-play-sharp-fill\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" viewBox=\"0 0 100 100\"><defs><style>.fp-color-play{opacity:0.65;}.controlbutton{fill:#fff;}<\/style><\/defs><title>play-sharp-fill<\/title><path class=\"fp-color-play\" d=\"M49.9217-.078a50,50,0,1,0,50,50A50.0564,50.0564,0,0,0,49.9217-.078Z\"\/><polygon class=\"controlbutton\" points=\"73.601 50 37.968 70.573 37.968 29.427 73.601 50\" filter=\"url(#f1)\"\/><\/svg><\/div><div class=\"fp-preload\"><b><\/b><b><\/b><b><\/b><b><\/b><\/div><\/div>\n\n<\/div>\n\n<p style=\"text-align: center;\">Myndband 1.2. Selta sj\u00e1var. Lj\u00f3sir litir benda til meira saltmagns en d\u00f6kkir til minna saltmagns. Sj\u00e1 m\u00e1 a\u00f0 Atlantshafi\u00f0 er saltara en Kyrrahafi\u00f0. Taki\u00f0 einnig eftir minna\u00a0saltmagni vi\u00f0 \u00f3sa st\u00f3rra flj\u00f3ta.<\/p>\n<h5><span class=\"arrow-pg\"><\/span><em><strong>Samlo\u00f0un og vi\u00f0lo\u00f0un<\/strong><\/em><\/h5>\n<p>\u00cd v\u00f6kvum eru a\u00f0 verki\u00a0<span style=\"background-color: transparent; color: #404040; display: inline; float: none; font-family: sans-serif; font-size: 15px; font-style: normal; font-variant: normal; font-weight: 400; letter-spacing: normal; line-height: 22.5px; orphans: 2; text-align: left; text-decoration: none; text-indent: 0px; text-transform: none; -webkit-text-stroke-width: 0px; white-space: normal; word-spacing: 0px;\"><span class=\"tooltips \" style=\"\" title=\"Kraftar sem verka \u00e1 milli sameindanna \u00ed v\u00f6kvanum.&lt;\/span&gt;&lt;span style=&quot;background-color: transparent; color: #404040; display: inline; float: none; font-family: sans-serif; font-size: 15px; font-style: normal; font-variant: normal; font-weight: 400; letter-spacing: normal; line-height: 22.5px; orphans: 2; text-align: left; text-decoration: none; text-indent: 0px; text-transform: none; -webkit-text-stroke-width: 0px; white-space: normal; word-spacing: 0px;&quot;&gt;\">sameindakraftar<\/span><\/span> sem koma fram sem samlo\u00f0unarkraftar inni \u00ed v\u00f6kvanum en sem vi\u00f0lo\u00f0unarkraftar \u00ed yfirbor\u00f0i hans. Hinir fyrrnefndu valda <span class=\"tooltips \" style=\"\" title=\"Seigja er m\u00e6likvar\u00f0i \u00e1 treg\u00f0u v\u00f6kva til a\u00f0 fl\u00e6\u00f0a; \u00ed daglegu tali er oft tala\u00f0 um \u00feykkt.\">seigju<\/span>, hinir s\u00ed\u00f0arnefndu yfirbor\u00f0sspennu. Seigjan er mikilv\u00e6g fyrir m\u00f6guleika svifs til a\u00f0 haldast \u00ed yfirbor\u00f0sl\u00f6gum. Seigja vex l\u00edtillega me\u00f0 vaxandi seltu en minnkar talsvert me\u00f0 h\u00e6kkandi hita. \u00dev\u00ed er erfi\u00f0ara fyrir svif a\u00f0 haldast \u00ed yfirbor\u00f0sl\u00f6gum hl\u00fdrri sj\u00e1var. Svifi\u00f0 vill au\u00f0vita\u00f0 vera \u00ed yfirbor\u00f0sl\u00f6gunum \u00fev\u00ed \u00fear sk\u00edn s\u00f3lin og pl\u00f6ntusvif n\u00fdtir s\u00f3largeislana til lj\u00f3still\u00edfunar. \u00dev\u00ed meira yfirbor\u00f0 sem svifi\u00f0 hefur mi\u00f0a\u00f0 vi\u00f0 r\u00famm\u00e1l \u00fev\u00ed meiri m\u00f3tst\u00f6\u00f0u veitir \u00fea\u00f0 og sekkur \u00fe\u00e1 s\u00ed\u00f0ur. \u00deess vegna hefur svif \u00e1 hitabeltsisv\u00e6\u00f0um fleiri anga og svifh\u00e1r (fallhl\u00edfar\u00e1hrif) en svif \u00e1 kaldari sv\u00e6\u00f0um. Samlo\u00f0unar- og vi\u00f0lo\u00f0unareiginleikar vatns eru einnig\u00a0 l\u00edfe\u00f0lisfr\u00e6\u00f0ilega mikilv\u00e6gir fyrir l\u00edfverur. \u00c6\u00f0akerfi\u00f0 \u00ed d\u00fdrum og h\u00e1r\u00e6\u00f0akerfi\u00f0 \u00ed pl\u00f6ntum er a\u00f0 mestu fyllt me\u00f0 vatni (bl\u00f3\u00f0i\u00f0 okkar er a\u00f0 miklu leyti vatn). Vegna samlo\u00f0unar og vi\u00f0lo\u00f0unar getur vatn flutt n\u00e6ringarefni og \u00fargangsefni b\u00e6\u00f0i \u00ed d\u00fdrum og pl\u00f6ntum.<\/p>\n<p>\u00dear sem vatnssameindir \u00e1 yfirbor\u00f0i la\u00f0ast sterkar a\u00f0 hvor annarri en a\u00f0 loftinu fyrir ofan \u00fe\u00e6r myndast yfirbor\u00f0sspenna. Sameindirnar \u00ed yfirbor\u00f0inu togast \u00fev\u00ed inn \u00e1 vi\u00f0, yfirbor\u00f0i\u00f0 ver\u00f0ur eins og sveigjanleg himna og f\u00e6r tilhneigingu til a\u00f0 dragast saman. \u00deess vegna geta t.d. sum skord\u00fdr gengi\u00f0 \u00e1 vatni. Yfirbor\u00f0sspenna eykst me\u00f0 vaxandi seltu, en minnkar me\u00f0 h\u00e6kkandi hitastigi og me\u00f0 vaxandi mengun. Yfirbor\u00f0sspenna \u00e1 sv\u00e6\u00f0um \u00fear sem mengun er mj\u00f6g mikil er oft talsvert l\u00e6gri en reiknu\u00f0 gildi mi\u00f0a\u00f0 vi\u00f0 hitastig og seltu.<\/p>\n<h5><span class=\"arrow-pg\"><\/span><em><strong>Varmar\u00fdmd<\/strong><\/em><\/h5>\n<p>Vatn hefur mikla varmar\u00fdmd, sem \u00fe\u00fd\u00f0ir a\u00f0 vatn getur dregi\u00f0 \u00ed sig mikinn varma \u00e1n \u00feess a\u00f0 skipta um fasa og ver\u00f0a a\u00f0 gufu. \u00deessi eiginleiki vatns temprar hitastig st\u00f6\u00f0uvatna og sj\u00e1var, en er einnig mikilv\u00e6gt l\u00edfe\u00f0lisfr\u00e6\u00f0ilega fyrir l\u00edfverur. \u00dear sem hitabreytingar \u00ed vatni gerast h\u00e6gt er au\u00f0veldara fyrir l\u00edfverur sem \u00fear lifa a\u00f0 halda s\u00ednu innra hitastigi.<\/p>\n<p>Varmaeiginleikar sj\u00e1var eru mj\u00f6g hagst\u00e6\u00f0ir fyrir l\u00edf \u00e1 j\u00f6r\u00f0inni. Haffl\u00f6turinn endurkastar a\u00f0eins litlu broti af orkunni sem lj\u00f3sgeislarnir varpa \u00e1 hann en drekkur st\u00f3ran hluta orkunnar \u00ed sig, dreifir henni me\u00f0 bl\u00f6ndun um \u00feykkt sj\u00e1varlag og hitar svo andr\u00famslofti\u00f0 \u00feegar \u00fea\u00f0 er kaldara en sj\u00f3rinn. Sj\u00f3r hefur miklu meiri\u00a0<span class=\"tooltips \" style=\"\" title=\"S\u00fa orka sem \u00fearf til a\u00f0 hita tilteki\u00f0 magn efnis um 1\u00b0C.\">e\u00f0lisvarma<\/span> en andr\u00famsloft og jar\u00f0vegur sem \u00fev\u00ed hitna \u00f6rar en hafi\u00f0. Aftur \u00e1 m\u00f3ti k\u00f3lnar sj\u00f3rinn miklu h\u00e6gar en landi\u00f0 og lofti\u00f0. Sj\u00f3rinn drekkur \u00fev\u00ed mikinn varma \u00ed sig \u00e1 sumrin \u00e1n \u00feess a\u00f0 hitna miki\u00f0 og skilar honum svo aftur \u00e1 veturna. Mismunurinn \u00e1 meginlandsloftslagi og \u00fathafsloftslagi stafar af \u00feessu. Hitasveiflur vi\u00f0 sj\u00f3inn eru talsvert minni en lengra inni \u00ed landi.<\/p>\n<p>Varmaeiginleikar sj\u00e1var breytast hins vegar miki\u00f0 ef hitastig sj\u00e1varbor\u00f0sins l\u00e6kkar ni\u00f0ur \u00ed frostmark og frekara varmatap lei\u00f0ir til \u00edsmyndunar. \u00de\u00e1 taka varmaeiginleikarnir mj\u00f6g \u00f3hagst\u00e6\u00f0a stefnu. Sj\u00e1var\u00eds ver\u00f0ur flj\u00f3tlega gr\u00e1hv\u00edtur vegna loftb\u00f3la \u00ed \u00edsnum og endurkastar meira en helmingi af lj\u00f3sorkunni sem \u00e1 hann fellur. S\u00e9 hann \u00feakinn snj\u00f3 e\u00f0a hr\u00edmi getur endurkasti\u00f0 numi\u00f0 meira en 80% af lj\u00f3sorkunni. Endurkast fr\u00e1 \u00eds e\u00f0a snj\u00f3 getur veri\u00f0 n\u00e6stum 100%. S\u00f3largeislarnir skila \u00fev\u00ed ekki lengur neinni umframorku eins og \u00feeir gera yfir opnu hafi, heldur ver\u00f0ur orkutap, og \u00edsyfirbor\u00f0i\u00f0 heldur \u00e1fram a\u00f0 k\u00f3lna. Aflei\u00f0ing \u00edsmyndunar er \u00fev\u00ed l\u00e6kkun \u00e1 hitastigi \u00edssins og \u00f6r v\u00f6xtur hans. Lofti\u00f0, sem kemst \u00ed snertingu vi\u00f0 \u00edsinn, k\u00f3lnar og \u00feegar kalt lofti\u00f0 dreifist myndast meiri \u00eds. \u00dev\u00ed getur sm\u00e1v\u00e6gileg l\u00e6kkun \u00e1 hitastigi sj\u00e1var \u00e1 \u00edshafssv\u00e6\u00f0unum ni\u00f0ur a\u00f0 frostmarki \u00feannig a\u00f0 \u00eds n\u00e1i a\u00f0 myndast, valdi\u00f0 skj\u00f3tri l\u00e6kkun lofthitans og \u00f6rri \u00fatbrei\u00f0slu \u00edssv\u00e6\u00f0anna. Aftur \u00e1 m\u00f3ti getur l\u00edtilsh\u00e1ttar h\u00e6kkun \u00e1 hita \u00feess lofts, sem streymir til haf\u00edssv\u00e6\u00f0anna, leitt til \u00edsbr\u00e1\u00f0nunar vi\u00f0 ja\u00f0ar \u00edssins, og \u00feegar br\u00e1\u00f0nunin er einu sinni hafin, getur h\u00fan haldi\u00f0 hratt \u00e1fram. \u00deetta stafar af \u00fev\u00ed, a\u00f0 \u00feegar \u00edsinn tekur a\u00f0 br\u00e1\u00f0na breytast yfirbor\u00f0seiginleikar hans \u00feannig a\u00f0 endurskinsh\u00e6fni hans snarminnkar. \u00deetta \u00e1 s\u00e9r sta\u00f0 \u00e1 vorin \u00feegar lofti\u00f0 hitnar \u00e1 haf\u00edssv\u00e6\u00f0unum og lei\u00f0ir til \u00f3tr\u00falega skj\u00f3trar \u00edsbr\u00e1\u00f0nunar.<\/p>\n<div id=\"attachment_1779\" style=\"width: 1210px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/himinnoghaf.is\/mengunsjavar\/wp-content\/uploads\/Mynd3.30-Isbirnir.jpg\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-1779\" class=\"wp-image-1779 size-full\" src=\"https:\/\/himinnoghaf.is\/mengunsjavar\/wp-content\/uploads\/Mynd3.30-Isbirnir.jpg\" alt=\"\" width=\"1200\" height=\"442\" srcset=\"https:\/\/himinnoghaf.is\/mengunsjavar\/wp-content\/uploads\/Mynd3.30-Isbirnir.jpg 1200w, https:\/\/himinnoghaf.is\/mengunsjavar\/wp-content\/uploads\/Mynd3.30-Isbirnir-300x111.jpg 300w, https:\/\/himinnoghaf.is\/mengunsjavar\/wp-content\/uploads\/Mynd3.30-Isbirnir-768x283.jpg 768w, https:\/\/himinnoghaf.is\/mengunsjavar\/wp-content\/uploads\/Mynd3.30-Isbirnir-1024x377.jpg 1024w\" sizes=\"auto, (max-width: 1200px) 100vw, 1200px\" \/><\/a><p id=\"caption-attachment-1779\" class=\"wp-caption-text\">Mynd 1.3. \u00deegar br\u00e1\u00f0nun \u00edss er hafin \u00e1 haf\u00edssv\u00e6\u00f0um getur h\u00fan haldi\u00f0 hratt \u00e1fram.<\/p><\/div>\n<h5><span class=\"arrow-pg\"><\/span><em><strong>E\u00f0lis\u00feyngdarbreytingar<\/strong><\/em><\/h5>\n<p>E\u00f0li flestra efna er a\u00f0 dragast saman vi\u00f0 k\u00e6lingu en \u00feenjast \u00fat \u00feegar \u00feau hitna. \u00deetta \u00e1 hins vegar ekki alveg vi\u00f0 um vatn \u00ed flj\u00f3tandi \u00e1standi. Vatnsdropinn er minnstur \u2013 og <span class=\"tooltips \" style=\"\" title=\"E\u00f0lis\u00feyngd er m\u00e6likvar\u00f0i \u00e1 \u00fe\u00e9ttleika efnis, \u00fe.e. hversu mikil \u00feyngdin er mi\u00f0a\u00f0 vi\u00f0 r\u00famm\u00e1l. E\u00f0lis\u00feyngd vatns vi\u00f0 4\u00b0C er 1 kg \u00e1 hvern l\u00edtra (\u00fe\u00f3 h\u00e9r s\u00e9 tala\u00f0 um e\u00f0lis\u00feyngd v\u00e6ri \u00ed raun r\u00e9ttara a\u00f0 tala um e\u00f0lismassa).\">e\u00f0lis\u00feyngd<\/span> hans \u00fear me\u00f0 mest \u2013 \u00feegar hitastig hans er 4\u00b0C en ekki 0\u00b0C eins og b\u00faast m\u00e6tti vi\u00f0. Vatn \u00feenst \u00fat \u00feegar \u00fea\u00f0 hitnar umfram 4\u00b0C, en <span class=\"tooltips \" style=\"\" title=\"Vatnssameindir h\u00e6gja \u00e1 s\u00e9r \u00feegar vatn k\u00f3lnar. \u00de\u00e1 eiga \u00fe\u00e6r ekki eins au\u00f0velt me\u00f0 a\u00f0 sl\u00edta sig hver fr\u00e1 annarri og t\u00edminn sem \u00fe\u00e6r lo\u00f0a hver vi\u00f0 a\u00f0ra lengist. Vi\u00f0 4\u00b0C er p\u00f6kkunin best og r\u00famm\u00e1li\u00f0 \u00ed l\u00e1gmarki en vi\u00f0 enn l\u00e6gra hitastig byrja sameindirnar a\u00f0 ra\u00f0a s\u00e9r upp \u00ed sexhyrninga \u00e1 svipa\u00f0an h\u00e1tt og \u00ed \u00edskrist\u00f6llum. Vi\u00f0 \u00fea\u00f0 a\u00f0 mynda sexhyrninga ver\u00f0ur til miki\u00f0 autt r\u00famm\u00e1l inni \u00ed mi\u00f0ju \u00feeirra og \u00edsinn hefur \u00fev\u00ed meira r\u00famm\u00e1l en vatni\u00f0 e\u00f0a sem svarar t\u00e6pum 10%. Fr\u00e1 4\u00b0C og ni\u00f0ur \u00ed frostmark eru \u00feessir sexhyrningar mj\u00f6g skamml\u00edfir og eru til \u00ed a\u00f0eins brot af sek\u00fandu. Vi\u00f0 frostmark er samt svo komi\u00f0 a\u00f0 hra\u00f0i sameindanna er or\u00f0inn of l\u00edtill til a\u00f0 \u00fe\u00e6r geti losa\u00f0 sig fr\u00e1 n\u00e1l\u00e6gum sameindum og \u00fe\u00e6r sitja \u00fev\u00ed fastar og geta ekki lengur fer\u00f0ast um - \u00edskristallar hafa myndast.\">vatn \u00feenst l\u00edka \u00fat \u00feegar \u00fea\u00f0 fr\u00fds<\/span>. \u00deess vegna fl\u00fdtur \u00eds \u00e1 vatni og st\u00f6\u00f0uv\u00f6tn botnfrj\u00f3sa s\u00ed\u00f0ur. Vi\u00f0 h\u00e1tt hitastig eru \u00e1hrif hitabreytinga \u00e1 varma\u00feenslu, og \u00fear me\u00f0 e\u00f0lis\u00feyngd, meiri en vi\u00f0 l\u00e1gt hitastig og n\u00e1l\u00e6gt frostmarki sj\u00e1var breytist e\u00f0lis\u00feyngdin l\u00edti\u00f0 \u00fe\u00f3tt hiti h\u00e6kki e\u00f0a l\u00e6kki. S\u00e9 hitinn hins vegar kominn upp fyrir 20\u00b0C hefur sm\u00e1v\u00e6gileg hitabreyting talsver\u00f0 \u00e1hrif \u00e1 e\u00f0lis\u00feyngdina. \u00c1 nor\u00f0l\u00e6gum sl\u00f3\u00f0um, \u00fear sem sj\u00f3rinn er kaldur, r\u00e1\u00f0a seltubreytingar mestu um e\u00f0lis\u00feyngdina, en \u00e1 heitum hafsv\u00e6\u00f0um er \u00fea\u00f0 hitinn sem mestu r\u00e6\u00f0ur.<\/p>\n<p>Hin \u00f3venjulega heg\u00f0un ferskvatns, sem hefur e\u00f0lis\u00feyngdarh\u00e1mark vi\u00f0 4\u00b0C, breytist verulega \u00feegar b\u00e6tt er \u00ed \u00fea\u00f0 s\u00f6ltum. \u00deegar seltan er 0 ver\u00f0ur h\u00e1markse\u00f0lis\u00feyngdin vi\u00f0 4\u00b0C og frostmarki\u00f0 er 0\u00b0C &#8211; hitastig h\u00e1markse\u00f0lis\u00feyngdar er \u00fev\u00ed fyrir ofan frostmarki\u00f0. Eftir \u00fev\u00ed sem seltan vex, n\u00e1lgast hitastig vi\u00f0 h\u00e1markse\u00f0lis\u00feyngd og frostmarki\u00f0 hvort anna\u00f0. \u00deegar seltan er 24,7\u2030 er h\u00e1markse\u00f0lis\u00feyngd vi\u00f0 sama hitastig og frostmarki\u00f0, e\u00f0a -1,4\u00b0C. Vi\u00f0 seltuna 24,7\u2030 liggja m\u00f6rkin milli d\u00e6miger\u00f0ra eiginleika ferskvatns og sj\u00e1var. \u00cd fersku vatni, t.d. vi\u00f0 7\u00b0C (e\u00f0a sj\u00f3 me\u00f0 seltu undir 24,7\u2030) vex e\u00f0lis\u00feyngd vi\u00f0 k\u00e6lingu. \u00deegar ferskvatn k\u00f3lnar vi\u00f0 yfirbor\u00f0 fer fram l\u00f3\u00f0r\u00e9tt bl\u00f6ndun (yfirbor\u00f0svatni\u00f0 sekkur) \u00fear til komi\u00f0 er ni\u00f0ur fyrir 4\u00b0C \u00fev\u00ed \u00fe\u00e1 fer vatni\u00f0 a\u00f0 l\u00e9ttast aftur (e\u00f0lis\u00feyngdin minnkar). Yfirbor\u00f0svatn sekkur \u00fe\u00e1 ekki lengur og l\u00f3\u00f0r\u00e9tta bl\u00f6ndunin h\u00e6ttir. Frekari k\u00e6ling n\u00e6r \u00fev\u00ed a\u00f0eins til \u00feunns yfirbor\u00f0slags sem getur frosi\u00f0 \u00e1 sk\u00f6mmum t\u00edma s\u00e9 lofthiti n\u00e6gilega l\u00e1gur. \u00cd miklum frostum myndu alldj\u00fap st\u00f6\u00f0uv\u00f6tn botnfrj\u00f3sa ef e\u00f0lis\u00feyngd vatnsins ykist s\u00edfellt vi\u00f0 \u00e1framhaldandi k\u00e6lingu. \u00dear sem e\u00f0lis\u00feyngd er mest n\u00e1l\u00e6gt 4\u00b0C hefur botnvatn dj\u00fapra st\u00f6\u00f0uvatna oft \u00fea\u00f0 hitastig og \u00e1framhaldandi k\u00e6ling n\u00e6r a\u00f0eins til yfirbor\u00f0slagsins sem ver\u00f0ur e\u00f0lisl\u00e9ttara og blandast \u00fev\u00ed ekki vatninu fyrir ne\u00f0an. Bl\u00f6ndun vegna hvassvi\u00f0ris getur \u00fe\u00f3 leitt til \u00feess a\u00f0 st\u00f6\u00f0uv\u00f6tn k\u00f3lni ni\u00f0ur \u00e1 talsvert d\u00fdpi.<\/p>\n<p>\u00cd sj\u00f3 ver\u00f0ur bl\u00f6ndunarferli\u00f0 allt anna\u00f0. Frostmark sj\u00e1var (selta: 35\u2030) er -1,9\u00b0C en h\u00e1markse\u00f0lis\u00feyngd er vi\u00f0 -3,5\u00b0C. E\u00f0lis\u00feyngdin eykst \u00fev\u00ed \u00fe\u00f3tt komi\u00f0 s\u00e9 ni\u00f0ur fyrir frostmark. S\u00e9 sj\u00f3rinn einsleitur gerir \u00e1framhaldandi k\u00e6ling hann \u00feyngri og l\u00f3\u00f0r\u00e9tt bl\u00f6ndun heldur s\u00edfellt \u00e1fram, \u00fe.e. kaldi yfirbor\u00f0ssj\u00f3rinn sekkur og k\u00e6lir sj\u00f3inn ni\u00f0ur \u00e1 meira d\u00fdpi. Vi\u00f0 sl\u00edkar a\u00f0st\u00e6\u00f0ur fr\u00fds sj\u00f3rinn \u00fev\u00ed ekki fyrr en \u00f6ll\u00a0<span class=\"tooltips \" style=\"\" title=\"\u00cdmyndu\u00f0 s\u00fala af sj\u00f3 fr\u00e1 yfirbor\u00f0i ni\u00f0ur a\u00f0 sj\u00e1varbotni.\">v\u00f6kvas\u00falan<\/span> er komin ni\u00f0ur \u00ed frostmark. \u00c1 hafi \u00fati yr\u00f0i \u00fe\u00e1 k\u00e6lingin v\u00ed\u00f0a a\u00f0 n\u00e1 ni\u00f0ur \u00e1 miki\u00f0 d\u00fdpi og geysilegt sj\u00e1varmagn a\u00f0 k\u00f3lna \u00e1\u00f0ur en sj\u00f3rinn frysi. K\u00e6ling sj\u00e1var ver\u00f0ur \u00fev\u00ed allajafna mj\u00f6g h\u00e6gfara og \u00fath\u00f6fin frj\u00f3sa ekki svo au\u00f0veldlega jafnvel \u00fe\u00f3tt frosth\u00f6rkur standi \u00ed langan t\u00edma. A\u00f0 \u00feessu leyti m\u00e1 segja a\u00f0 reginmunur s\u00e9 \u00e1 heg\u00f0un ferksvatns og sj\u00e1var. En n\u00fa eru au\u00f0vita\u00f0 m\u00f6rg d\u00e6mi \u00feess a\u00f0 \u00eds myndist \u00e1 hafinu. \u00deegar \u00fea\u00f0 \u00e1 s\u00e9r sta\u00f0 er venjulega um lagskiptan sj\u00f3 a\u00f0 r\u00e6\u00f0a, \u00fear sem seltuminni og e\u00f0lisl\u00e9ttari yfirbor\u00f0ssj\u00f3r fl\u00fdtur ofan \u00e1 saltari og \u00feyngri sj\u00f3. Ef mismunur \u00e1 e\u00f0lis\u00feyngd sj\u00e1varlaganna er n\u00e6gilega mikill, n\u00e6r l\u00f3\u00f0r\u00e9tta bl\u00f6ndunin, sem k\u00e6lingin \u00e1 yfirbor\u00f0i veldur, a\u00f0eins ni\u00f0ur a\u00f0 skilum sj\u00e1varlaganna. Vi\u00f0 sl\u00edkar a\u00f0st\u00e6\u00f0ur k\u00f3lnar yfirbor\u00f0slagi\u00f0 \u00e1 sk\u00f6mmum t\u00edma og \u00eds getur au\u00f0veldlega myndast.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Vatn (H2O) er eina n\u00e1tt\u00farulega efni\u00f0 \u00e1 j\u00f6r\u00f0inni sem finnst \u00ed \u00f6llum \u00feremur f\u00f6sum: frosi\u00f0 (\u00eds), flj\u00f3tandi (vatn) og sem lofttegund (vatnsgufa). Vatn er nau\u00f0synlegt \u00f6llu l\u00edfi, eins og vi\u00f0 \u00feekkjum \u00fea\u00f0. Frumur eru a\u00f0 miklu leyti vatn, e\u00f0a um <a class=\"more-link\" href=\"https:\/\/himinnoghaf.is\/mengunsjavar\/index.php\/2017\/09\/17\/1-3-eiginleikar-vatns-og-sjavar\/\">Lesa meira&#8230;<\/a><\/p>\n","protected":false},"author":2,"featured_media":1000,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[],"class_list":["post-176","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-01-umsjoinn"],"_links":{"self":[{"href":"https:\/\/himinnoghaf.is\/mengunsjavar\/index.php\/wp-json\/wp\/v2\/posts\/176","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/himinnoghaf.is\/mengunsjavar\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/himinnoghaf.is\/mengunsjavar\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/himinnoghaf.is\/mengunsjavar\/index.php\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/himinnoghaf.is\/mengunsjavar\/index.php\/wp-json\/wp\/v2\/comments?post=176"}],"version-history":[{"count":45,"href":"https:\/\/himinnoghaf.is\/mengunsjavar\/index.php\/wp-json\/wp\/v2\/posts\/176\/revisions"}],"predecessor-version":[{"id":3893,"href":"https:\/\/himinnoghaf.is\/mengunsjavar\/index.php\/wp-json\/wp\/v2\/posts\/176\/revisions\/3893"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/himinnoghaf.is\/mengunsjavar\/index.php\/wp-json\/wp\/v2\/media\/1000"}],"wp:attachment":[{"href":"https:\/\/himinnoghaf.is\/mengunsjavar\/index.php\/wp-json\/wp\/v2\/media?parent=176"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/himinnoghaf.is\/mengunsjavar\/index.php\/wp-json\/wp\/v2\/categories?post=176"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/himinnoghaf.is\/mengunsjavar\/index.php\/wp-json\/wp\/v2\/tags?post=176"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}