As shown from above, the average change in the mass of the spirit burner is 0.68 0.02g, which indicates that there was 0.68.02g of ethanol was used to heat water to have temperature difference of 30C. This needs to be changed into Kelvin as the formula requires the temperature to be in Kelvin. As the 30C is the temperature difference, therefore the temperature difference in Kelvin will be 30K. With this information, it is possible to find out the energy density of ethanol. Energy density is amount of energy produced per kilogram.
To find the quantity of thermal energy of water, Q, the formula Q = mc?t could be used where s is the constant which has 4.18JK-1g-1 value. In this formula, m is the mass and ?t is change in temperature. There was 50ml of water heated therefore m is 50g. As m equals to 0.68g and ?t equals to 30K, if we substitute these values to the formula; There is 65% difference between the data gained and theoretical data.
The uncertainty of gained data is 0.7MJ/kg. As the theoretical value is 26.8MJ/kg, it does not lie in between the uncertainty range. This is because of random error carried out throughout the whole experiment. As there are heat loss during the process of heating the water, there are a lot of heat being used heating up the surroundings, hence there are so much difference between the theoretical value and the gained value.
A was graph was not required to be drawn for this experiment. Since there is no change in any of the variables, as the change in temperature was kept constant and the amount of water used was also constant, therefore there were no independent or dependent variables. Hence a graph cannot be drawn to aid in the calculation of the energy density of ethanol There was three equipment used which affected the uncertainties. As weighed with electronic weight, there is systematic error in the weight itself. Also there is systematic error when water was measured with the 100ml measuring cylinder. Furthermore, in measuring the change in temperature, there is also a systematic error in reading the thermometer.
There were a lot of calculations been processed in order to calculate the energy density. All of those calculations had uncertainties included. These uncertainties built up throughout the calculations and ended up with 0.7MJ/kg. Since there is no graph needed in this experiment, it is unable to find out whether the best fit line lies in between the uncertainty marks in the graph. Random error was carried out throughout the experiment. When the spirit burner was heating water, before the heat reached water, the heat contacted with the beaker and the surrounding air. Therefore, a lot of heat was loss during the process of heating the water.
Heat loss due to the surrounding affects the heat flowing into water because the heat is also being used up within the process of heating water Create a wall, made out of cooking foil, around the spirit burner and the beaker to reduce heat flowing out and allowing heat to transfer directly to the beaker The number of trials performed due to lack of time As the number of trials increases, then the uncertainty will be reduced as there are more data points and allows cutting out data which are out of the range. Perform the experiment over a large quantity of times.
No temperature difference As there was no change in temperature difference, no graph was able to be created. By having a change in temperature difference and create a graph, then more accurate data would be gained. Room atmosphere The room atmosphere varies therefore affects the flame Try to create closest condition to STP by turning off the air conditioner and closed windows
Thomas, George. Overview of Storage Development DOE Hydrogen Program [pdf]. Hydrogen Program Review. San Ramon, CA. May9-11, 2000.