arun’s blog

Global warming has certainly become a much debatable topic, though the debate itself is what has partially led to the awareness in spite of its uncertainty. The inconclusiveness also has resulted in innumerous (constructive?) antagonism amongst various researchers, each of who possess a charismatic charm in convincing us with their theories corroborated with evidence and more than enough evidence to denigrate others’ results that they confabulated or concocted those. The denouement of this long perpetuating argument should be arrived sooner or later.

The number of seasons a region or country experiences is seemingly declining in the Southern India. A few years back, I could say we had at least 3 seasons; summer, very brief winter and rainy. But the situation now seems to give the impression that at least Chennai has only summer season throughout the year having become impotent of the other seasons, a blunt non-statistical inference though. However, in Germany, its already around -4 to -12 degree Celsius and counting. What is the funny but rather irritating consequence (I am not discussing Global warming)? It takes about 10 minutes to gear up with every piece of clothing you have, including thermal wears, t-shirt, another t-shirt, a sweater, jean, ear-bands or khullahs, neck-scarf(??) , gloves and finally a jacket minimum. This is similar to that of funny olden day Tamil Heroes getting loaded with shiny leather jackets, armors, hand grenades, machine guns bla bla… near the climax of the movie to slay the Villain and free the heroine after which they live happily ever after (Even Arnold Schwarzenegger movies!!). And what is even more irritating is, due to the presence of heaters inside the building (which is indispensable) some of the clothes have to be taken off to stop sweating.

Also sometimes the gloves aren’t that protective and you still require more warmth. It was not long before I came across this simple but intriguing heat device. It was some sort of a liquid along with what seemed like a switch. On pressing the switch, the liquid undergoes an immediate transition to solid phase and in the process generates heat, an exothermic reaction. My ignorance lead to a sense of bafflement over such a sophisticated and ingenious method of generating heat. How? This is where Sodium acetate, CH₃COO^-Na⁺ comes into picture. I quote from Wikipedia rather than trying to rephrase it. Awesome!

Sodium acetate is also used in consumer heating pads or hand warmers and is also used in “hot ice”. When sodium acetate trihydrate crystals (melting point 58 °C) are heated to around 100 °C, they melt. When this melt cools, it gives a supersaturated solution of sodium acetate in water. This solution is capable of supercooling to room temperature, well below its melting point, without forming crystals. By clicking on a metal disc in the heating pad, a nucleation center is formed which causes the solution to crystallize into solid sodium acetate trihydrate again. The bond-forming process of crystallization is exothermic, hence heat is emitted. The latent heat of fusion is about 264–289 kJ/kg (Source).

Also, I came across this video which should give a better understanding. (Courtesy and credits)