In our Science Co-op class, we were introduced to our Thermos Challenge project. The goal was to design and build your own homemade Thermos that prevented 150 mL of water from losing heat. With a budget of only $4 ($3 for thermos and $1 for wiring), our group decided to make a “hot” thermos that used electricity to maintain a steady inner temperature. This prevented the water inside from losing an excessive amount of heat. We also made a penguin cozy to keep it warm!







To begin, remove the top of the pop can. You can do this by using a knife to cut where the pop can will begin to slant inwards. Once removed, fold the sharp edges of the base of the pop can inwards. The top of the pop can may be thrown out.  


Next, trace the diameter of the pop can onto a sheet of cork (you will need two circles). These cork circles can then be glued to the inside of a small mason jar lid. Once inserted and glued into the lid, line the interior wall of the mason jar lid with felt and cut any excess that may stick over the top. To complete the lid, fold one piece of electrical tape over the edge of the wall (so that it sticks to the interior felt as well as the metal on the outside of the lid). 


The next step is to measure the can cozy to size. Place the lid that you have just created on the pop can. With the lid still, put on the can cozy. Our can cozy did not have a bottom however, if your can cozy does have a bottom, you can ignore this next step.  Cut the can cozy 2mm below the bottom of the can. With the extra fabric, cut a circle and sew this circle onto the bottom of your can cozy. You may now place your pop can into your cozy and make sure everything fits. 


As long as your lid, cozy and pop can all fit, you may move onto this next step. Remove the pop can from the can cozy. Off to the side, measure 3 metres of copper wire. Sand the ends of the wire (as copper wire has a coating), so that you can get an electrical current. Carefully wrap your copper wire evenly spaced around the pop can. Make sure to leave approximately 10 centimeters of extra wire on both ends of the can so it can come out of the beaker and attach to the (14-volt) battery.


To assemble the thermos, you must now place the can cozy onto the pop can that has been covered in wire (be careful not to move the wire too much). Place this pop can with the can cozy into the 400 mL beaker with the Copper wires feeding out of the pouring spout. If you choose to decorate your thermos, now is the time. We chose to make ours look like a penguin.

The final step is to connect your copper wires to the battery and wait as your thermos heats up. You can choose to pour your water in at any time! 


During Experiment:

Below is our thermos attached to a 14-volt battery using copper wires. A probe is then dropped into the water inside the thermos through a wire. This device tracks the temperature, shown on the digital thermometer.



The basics of our design started with a pop can wrapped in copper wire. We chose to use the tin can due to its high thermal conductivity. This allowed the heat transferred from the 14-volt battery to be easily transferred to the pop can, therefore warming the water. Our lid was constructed of a metal mason jar lid lined with cork and sealed with felt and a layer of tape. The Cork allowed for minimal heat loss because of its very low conductivity (0.035) and the lining of felt and tape allowed for a tight seal around the pop can when the thermos lid was put on. Lastly, on the lid we allowed for water vapor to escape through a small hole in the centre of the metal lid. We decided to have our thermos attached to the 14-volt battery to allow for maximum heat conservation in the can. While the water was being maintained at 98-102 degrees Celsius from the battery the water vapor escaped through our lids hole to allow for the pressure inside the can to release. Just under the lid, around the pop can and copper wires we used a foam cup cozy to contain the heat produced by the wire and ensure the heat was directed towards the water not the glass beaker.


Finally, our outer layer of the thermos was the glass beaker and the penguin cup cozy. The glass beaker was our last addition to allow for minimal heat loss. Glass has a relatively low thermal conductivity (1.0) which helped alongside the penguin cup cozy to maintain heat and allow for optimal aesthetics.


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