Our goal for this project was to create a thermos from cheap materials totaling to no more than $3. To create an efficient thermos, applications of our energy unit are necessary. Mine and Ethan’s thermos was simple and flawless in theory, to begin with, we took a Styrofoam cup and lined the inside with tin foil and created a lid out of tin foil and cotton fabric, these were the main functional components of the first prototype, as an additional aesthetic piece we painted it black. this thermos did not work well because it had a lack of insulation on the outside. 
Considering the poor results of our first thermos we decided to ditch the aesthetic of the paint and replace it with more insulation because to us functionality was more important, we used the same lid but replaced the paint with a layer of foam underlay which was the best insulator available to us
Our second thermos was our best performing thermos but it had one key issue in the fact that it was over budget by 45 cents, so we exchanged some of the tin foil for a cutout from a pop can which was less reflective but way cheaper at the same time, the outer layer of the second one was perfect so we kept that largely untouched besides using some of our freed budget to insulate the top better, these elements left us with our third and final thermos.
Despite this being our final product it was not our best performing, but it was our most cost effective thermos, the next worksheets outlines what we used in and how we performed the testing experiments and the over all results of all 3 thermoses.
Now, the most important part, the theory behind our design and why we believed it would work. I think it is worth mentioning that our thermos was the best performing thermos that only used materials found in class when taking into account the over all price of our final product. Our design is simple and focuses largely on keeping the heat inside by using reflective and conductive materials, if the inner layer is able to conduct heat well it will create a system where the water heats up the foil and then in turn the foil does the same to the water. of course because of the laws of energy conservation this does not work that perfectly in practice because the water must share its energy with the foil to heat it up causing the water to cool down slightly, and the foil will also share its energy with the insulators. Due to these reasons you put the conductor on the inside because it takes less energy to change its temperature so the water will lose minimal energy creating stable temperatures, in turn you keep the insulators on the outside because they do not conduct energy well so they aren’t good at introducing theenergy air outside. This is good because the hot water would balance its energy with the air faster if it had easier contact and more direct contact.