The Dark Side of Heat Measurement
Calorimeter by Keegan, Austin and Beth
Using a well-controlled experiment to explore how the different methods of heat transfer (convection, conduction, radiation) are used in a calorimeter.
Our calorimeter is extremely basic. We used aluminum foil to reflect radiant heat waves. Styrofoam was used to insulate the beaker, which held the water. This stops heat loss by conduction. We chose to use a beaker instead of a pop can because glass has a lower specific heat capacity than aluminum. sealing the outside and lid with tape was an ideal way to prevent convection, this trapped the heated air within the calorimeter, preventing energy loss to the external environment.
Our first test went as we expected. Our calorimeter achieved a temperature change of 12.6 degrees Celsius over a time period of 5 minutes, using 0.24 g of candle wax. Total heat: q=11.54 J. The increase in heat was relatively linear and uniform - as displayed on the graph below:
In order to explore the impact of radiant energy in heat transfer, we covered the transparent bottom of the beaker with opaque, black paint. This adjustment poses two interesting questions. Does radiant energy play a role in heating the water and will the black paint prevent the heat from being transferred? Having black paint could also capture more light rays and retain heat because of black's characteristic of absorbing all rays from across the visible spectrum.
Modified Calorimeter Results
As you can see from the above graph,the black paint had an impact on heat captured. No longer do we have a consistent linear graph. We used .32 grams of wax and achieved a change in heat of 14.5 degrees Celsius. This resulted in a total heat of q= 19.3952.We have a few hypotheses about what this could mean. The total retention of heat was greater in the modified calorimeter.
The greater increase in heat suggests that perhaps the absorption tendencies of the colour black affected heat transfer. Consult the following video for further information on how colours and light (radiant energy) affect heat transfer:
In terms of the inconsistent nature of the the modified calorimeter's rise in temperature, we wonder if the heat transferred through the black paint was passed to the water at irregular rates due to the black paint on both the outside and inside of the bottom on our calorimeter. The diagram below shows an enlarged view of the area affected by the paint. Our hypothesis is that the radiant energy from the candle would cause a temperature rise in section 1. We hypothesize that the paint has a higher specific heat capacity than the glass beaker which would slightly delay transfer of heat from section 1 to section 2. As the heat is then passed through section 2, it would encounter another layer of paint (section 3.) This would cause yet another delay in the heat being transferred to the water for measurement, resulting in a non-linear increase in heat, as depicted in the graph of our findings.
In order to determine what actually happened when the black paint was added to the calorimeter1 One of the options would be to change the colour of the paint, because we know that different colours absorb heat differently, we could prove that black is the best colous to use, for maximum heat capture. 2 By painting one side we could see if that allows for a faster increase of the heat because its one less medium to go through, and one less level to heat. 3 The opaqueness of the glass should prevent radiation which means that we don't need to put the aluminum foil around the beaker, by testing this and keeping the rest of the variables the same, we'll know if radiation is passing through the bottom of beaker.