CHEMISTRY BEHIND OUR HAND WARMER
Endothermic reactions - chemical reactions that absorb heat Exothermic reactions - chemical reactions that release heat Calcium Chloride and Water - representation of the reaction, CaCl2 (s) + H2O(l)--> Ca(+2) (aq) + 2Cl(-) + H2O(l), Calcium Chloride and Water combine in an exothermic reaction where heat is created through the separation of the calcium and chloride molecule bonds using water as its means to break down. Vermiculite - a hydrous phyllosilicate mineral, expands when heated and contains air pockets and a very minor amount of water. In our product we used this as one of our key insulators since it has air pockets to heat up and expands creating a larger surface area to contain the heat. Activated Charcoal - is thermally conductive, this helps in spreading the heat through out the hand warmer. Iron Powder - is conductive, helping our product retain heat for longer. |
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Reflection
Over all this project went very well and we were able to complete the task of designing and creating a hand warmer that has at least a twenty degree jump. We went through a few different models of our hand warmer staring with a balloon exterior, then to plastic freezer bag with lithium chloride, and finally settled on the calcium chloride solution in the plastic freezer bag with a polyester case around it. The reason in the end why we chose to use calcium chloride and a freezer bag was that it made our product cheaper and more reliable. The judges had a hard time breaking the inner plastic bag to release the water to start the reaction but it showed that our bag could withstand a lot of physical strength. Despite our effort put into creating our had warmer, ours wasn't the best environmentally, only the outer case was reusable, and it wasn't extremely cheap, so we found a way to sell our product to make an appropriate profit basing our product on a business standpoint. We would sell the product in different ways to make more money and continually make a profit from people needing to buy refills which in the end ended up being the best business model even though it may not have been the best economically speaking. Even though we would have liked our product to be environmentally safe by being reusable we discovered that wasn't totally possible with our prototype and instead focused on the money aspect and selling positives of our bag, to raise funds for our schools sports programs and STEM program. Through out this project, we learned about using exothermic reactions to create heat and recapped on thermodynamics to retain as much heat as possible. If we were to do this project again I would have liked to spend more time researching new methods of hand warmers and creating a business model to connect with our hand warmer. In the end, our project was a success in that we completed our task but if we had more time or resources we could have improved our latest prototype and created one that would sell a lot and be economic.