{"id":630,"date":"2013-09-02T23:06:37","date_gmt":"2013-09-02T11:06:37","guid":{"rendered":"https:\/\/blog.waikato.ac.nz\/physicsstop\/2013\/09\/02\/temperature_and_heat\/"},"modified":"2013-09-02T23:06:37","modified_gmt":"2013-09-02T11:06:37","slug":"temperature-and-heat","status":"publish","type":"post","link":"https:\/\/blog.waikato.ac.nz\/physicsstop\/2013\/09\/02\/temperature-and-heat\/","title":{"rendered":"Temperature is not Heat"},"content":{"rendered":"<p> First things first. PhysicsStop is back on-line after an enjoyable two-week break in warm and sunny southern England.<\/p>\n<p> Second things second. What advice can anyone give to the parents of a fourteen-month-old with jetlag who insists that 4 am is time to get up, have breakfast, and feed the chickens (or the &quot;Choo Chuk&quot; as he calls them)? In the end we got up, had breakfast and let the chickens and the neighbours get some sleep. Consequently I&#039;m rather tired and feel like it&#039;s ten past two, not ten past eleven.&nbsp;<\/p>\n<p> So, here&#039;s a bit of quick physics from our travels. If you&#039;re fortunate enough to fly with an airline that still gives out hot towels to its economy class passengers, you&#039;ll know that the towels can be extremely hot &#8211; almost untouchable at first. But, once you&#039;ve unrolled them and used them for whatever purpose you can think of, they cool down very rapidly. They don&#039;t stay hot for long, and you hand them back cold.<\/p>\n<p> In physics terms, the towel, as it is presented to you, has a high <u>temperature,<\/u> but it doesn&#039;t have a great deal of <u>heat<\/u>. While we can use these words loosely and almost synonomously in everyday conversation about the weather, in physics they are very distinct quantities. Heat is a measure of the thermal energy in something. It&#039;s measured in joules, just like any other form of energy. The energy resides in the thermal vibrations of the water molecules. Heat is an <u>extrinsic<\/u> quantity. If one doubled the amount of the material (had a towel twice as big), one would have twice the amount of heat.&nbsp;<\/p>\n<p> Temperature is a lot harder to define in simple terms. (Try making sense of the <a href=\"http:\/\/en.wikipedia.org\/wiki\/Temperature\" target=\"_blank\">Wikipedia entry on it<\/a>). There&#039;s a nice physical definition (rate of increase of energy with respect to entropy) but that&#039;s not terribly intuitive. It&#039;s easier to think of temperature as an &#039;average&#039; thing &#8211; broadly speaking temperature is proportional to the average kinetic energy per atom in the material. Each atom in something that&#039;s hot will have more kinetic (movement) energy than something that&#039;s cold. Any physicists reading this will realise I&#039;ve given a horribly simplistic definition, but it is roughly correct. A key thing is that temperature is an <u>intrinsic<\/u> quantity &#8211; if you double the amount you have (a towel twice the size), the temperature (average energy per atom) stays the same.<\/p>\n<p> Our towel starts at a high temperature. However, because it is thin, there isn&#039;t actually a lot of heat in it. That means that it quickly loses what heat it had once unrolled, and the temperature, which is what you perceive on your skin, drops. &nbsp;Contrast this to a lump of rock that&#039;s been sitting in your oven at 70 degrees for five hours. Pick that out and see how long you can hold it for (actually, don&#039;t try it). It contains far more heat than a hot towel, so it takes much, much longer for it to be lost.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>First things first. PhysicsStop is back on-line after an enjoyable two-week break in warm and sunny southern England. Second things second. What advice can anyone give to the parents of a fourteen-month-old with jetlag who insists that 4 am is time to get up, have breakfast, and feed the chickens (or the &quot;Choo Chuk&quot; as [&hellip;]<\/p>\n","protected":false},"author":20,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[9,13,14],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v22.5 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Temperature is not Heat : Physics Stop<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/blog.waikato.ac.nz\/physicsstop\/2013\/09\/02\/temperature-and-heat\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Temperature is not Heat : Physics Stop\" \/>\n<meta property=\"og:description\" content=\"First things first. 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