An experiment to measure the specific heat capacity of water
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An Experiment to measure the Specific Heating Capacity of Water by electrical heating Method Put a known mass of water in a beaker and then immerse the heating coil in the water. Connect the heating coil to a DC power supply. Include an ammeter and a voltmeter in the circuit to measure the current through the coil and the voltage across it. Switch on the current in the coil and leave it until a reasonable temperature increase has been recorded. Measurements We recorded the starting temperature and the highest temperature reached during the experiment. We recorded the time for which the current was flowing and we measured the current and voltage throughout the heating interval. We recorded all of our measurements which are shown below. Before commencing the experiment, we considered what precautions we could take to ensure accuracy. First we changed to a smaller beaker as this would give us less volume of water to heat, enabling us to complete the experiment within the designated time. We also felt that we gained the following advantages * Less water surface area = less heat loss from water * Less beaker surface area = less heat loss from beaker & less heat to warm up beaker * Less water volume
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.
= 0.185 2 0.185 0.1 Change in water temperature (ºC) 22.5 (+/- 0.25) + (+/- 0.25) =0.5 Not applicable +/- 0.5 2.2 Current (I) 1.89 +/- 0.005 (1.89-1.87) =0.01 2 0.01 0.5 Voltage (v) 9.93 +/- 0.005 (9.96 - 9.90) = 0.03 2 0.03 0.3 Time (secs) 930.39 +/- 0.005 Not applicable +/- 0.005 0.0000054 Total % error 3.1 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 1/2 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.
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