We proceeded to insulate this beaker with two layers of bubble wrap and 2 layers of felt and then placed the beaker on a further to layers of bubble wrap as an extra precaution to prevent heat loss errors.
We considered the heat used to warm up the thermometer but decided that there was little we could practically do to reduce this error in this experiment.
We also considered the effect of the heat of the room on the experiment and so decided to start with the water temperature below room temperature and heat it to an equal amount above room temperature to compensate. Any heat gained from the room in heating the water to room temperature should counteract any heat lost to the room when heating the water above room temperature.
We considered the risk of uneven heating of the water and decided to stir the water with the thermometer prior to taking the reading. The stirring was done prior to reaching the time that the reading was due to ensure accurate timing of readings.
We decided that we needed a temperature change of at least 10 ºC to provide us with enough data. Note – for consistency and to reduce errors from calibration, the same scales and thermometer were used throughout.
When we commenced our experiment, we took the following readings
Empty Beaker = 95.98gm, weighed on digital scales
Beaker and cold water = 289.96g, weighed on digital scales
Initial water temperature = 16 ºC, taken with a standard thermometer
Room temperature = 24ºC, taken with a standard thermometer
Difference in temperatures = 8ºC
This meant heating the water to 32ºC to give an equal number of degrees above and below room temperature and meant that we had an overall temperature change of 16ºC which we considered reasonable. However, shortly after commencing the experiment, our current reading dropped to 0. On investigation of the circuit, it appeared that the heating element had become detached from the crocodile clips thus breaking the circuit. We considered the effect of this on the experiment such as the temperature increase from the heating which had already taken place, potential heat loss whilst the heater was disconnected and water loss from retrieving the heater from the beaker. We felt that the errors which had occurred in rectifying the situation were too great to continue and so we began the experiment again.
This time, we managed to achieve a colder start temperature for the water and so our starting readings were.
Empty beaker = 95.98g
Beaker plus cold water = 296.26g
Initial water temperature = 13.5ºC
Room temperature = 24ºC
This gives a temperature difference of 10.5ºC and so we needed to heat our water to 34.5ºC, giving us a total temperature difference of 21ºC which we were very happy with. We decided to take measurements at every minute and recorded the following results.
We stopped collating information at 14m 30.39s as we had reached our target temperature. At this point the power supply was turned off. We did however continue to time the increase in temperature until it started to drop, this being the maximum temperature reached by the water. We recorded this at a time of 18m 50.00 secs.
At this point, we weighed the beaker and water again.
Beaker plus warm water = 295.89g
Difference in water from start to end of experiment = -0.37g
No steam or evaporation was noticed. We felt that it was therefore reasonable to assume that the majority of this missing water was probably on the removed coil.
Theory
We know that
E = m s ΔT but E = VxQ = V x (I x t)
So, V I t = m s ΔT
Inserting our figures gives
S = V I t = (9.93 x 1.89 x 930.39) = 17461.2804 = 3880.284533 j/kgºC
m ΔT (0.200 x 22.5) 4.5
Therefore, the figures from our experiment have provided us with a Specific Heat Capacity of 3880.28 (to 2dp). However, we need to consider the below errors to reach a more accurate figure.
Errors
After considering the above table of errors, we amend our figure for Specific Heat Capacity of water as follows
3880.28 +/- (3.1% x 3880.28) = 3880.28 +/- 120.28 j/kgºC
The largest source of error in reaching this solution was the thermometer used to read the temperature, as it was the ½ division that we used to calculate the error. In order to improve this in a repeat experiment, we would need to find a more accurate thermometer.
Ideas for further research
We could consider the Specific Heat Capacity of water in different environments eg. Under pressure? Surrounding temperature – extreme heat versus extreme cold?
We could compare the Specific Heat Capacity with that of other substances to investigate the differences and why the Specific Heat Capacity of Water is so high.
We could mix water with other substances to investigate the effect on the Specific Heat Capacity of both substances.
