Convection, Conduction & Radiation
By Matt & Hilary
Conduction - Transfer of heat due to vibrating or touching particles.
Convection - Flow of hot air or liquids rising (hot air rises).
Radiation - Transfer of heat from a source by waves/radiation.
What is it?
The purpose of this experiment is to design and construct a handmade Calorimeter using the three essential components of conduction, convection and radiation. After constructing a calorimeter and testing its effectiveness using all three components, we are asked to subject the calorimeter to one change. We then ask the question of "I wonder what would happen if...?" and carry out a well controlled experiment documenting our findings involving the change.
To begin the project we designed an effective yet simplistic calorimeter that could easily be changed to meet the criteria of our scientific "what if" question. The materials used include: two cardboard kleenex boxes, one small cardboard box, cotton balls, aluminum foil, the top of a balloon, a pop can, a tea light candle and electrical tape. The pop can was filled with 100mL of water.
Conduction, Convection and Radiation are maintained by various materials in our calorimeter. The cotton balls used for insulation are in place to prevent heat from escaping the can through the metal. This is how conduction was controlled. The aluminum foil lining in the box holding the candle, is used to ensure that heat waves from the candle are being reflected back towards the pop can. This controls radiation. Lastly, the balloon piece covering the opening of the can is used to ensure that the circulation of hot air in the can is maintained and does not escape. This is how convection is controlled.
Obtaining the Data
Once we assembled our calorimeter we did several test runs to ensure everything was working properly. We then set up to collect the data from our calorimeter to begin the first half of the experiment. We used the graphing software of LoggerPro to collect and document our data in tables and graphs. The software was set up to record the temperature of the water every 30 seconds. Therefore we collected two samples per minute. We conducted the experiment for 15 minutes.
Before the Change
In the first part of our experiment the initial temperature of the 100mL of water was 23.5 degrees celsius. Over the course of 15 minutes the temperature of the water rose 46.9 degrees celsius. The final temperature of our water was 70.4 degrees celsius. Based on these results we can conclude that our calorimeter was very effective.
The next step in our experiment was to ask ourselves a scientific question. What would happen if we made a change to the calorimeter? What would our data reveal? The question we decided to ask ourselves is what would happen if we eliminated convection? If the three components of convection, conduction and radiation are required in order for a calorimeter to function at its best, then what would happen if we eliminated one of the components? We are taking away one of the key components of a calorimeter, therefore isn't a change in the data inevitable?
After establishing a scientific question, we needed to apply the change to our calorimeter. We chose to eliminate convection. To accomplish this we removed the balloon covering from the opening of the pop can. We also cut a medium to large hole in the middle of the uppermost box in order to expose the opening of the can. By doing this we have eliminated the presence and control of convection. the following pictures demonstrate the changes that were made.
After applying the changes to the calorimeter the next step was to collect the data using the same software as in the first experiment. Once again we used 100mL of water and also used the same candle. We conducted the second experiment over the course of 15 minutes and the sample rate was also the same as the previous experiment. Everything involved in the second half of the experiment was kept the same except for the elimination of convection. The initial temperature of the water for the second experiment was 23.1 degrees celsius. Over the course of 15 minutes the temperature only rose 35.2 degrees celsius. The final temperature of the water was 58.3 degrees celsius. The following pictures display our results.
What's the Big Deal?
Based on the results we have obtained from the changed calorimeter we can make several conclusions. The first is that convection does indeed play an important role in a properly working calorimeter. By eliminating convection from the calorimeter we have allowed a significant amount of heat to escape therefore resulting in a loss of heat from the water. Without a mechanism in place to prevent hot air from rising and escaping a lot of heat can be lost. The calorimeter simply does not work as efficiently when convection is eliminated. When we first asked ourselves the question we initially thought that eliminating convection would have an affect but not one this significant.
Upon completion of this experiment we were faced with the question of what we would do for further experimentation. We both agreed that if eliminating convection caused this much of a loss in heat and efficiency, we are curious to see what would happen if we eliminated radiation and conduction in place of convection. To eliminate radiation we would remove the aluminum foil and to eliminate conduction we would remove the cotton balls used for insulation. Based on our previous findings we can hypothesize that eliminating these two other components will also have and effect on the loss of heat and efficiency.