Keith Chan
Data Collection
Thermometer Sulphuric acid
Capillary tube Clamp & stand Air trapped 600mL Beaker Water Tripod
Bunsen burner
Dia. 1 Labelled diagram of the apparatus
Temperature of water at room temperature: 19oC Length of column at room temperature: 0.012 m Unc. in length of column at room temperature: 0.001 m Temp. / oC 24 34 44 54 64 74 84 94 100 Unc. in temp / oC 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Temp. / oC 24 34 44 54 64 74 84 94 100 Length of Column / m When heating 0.012 0.013 0.013 0.014 0.014 0.015 0.015 0.015 0.015 When cooling 0.012 0.012 0.013 0.013 0.014 0.014 0.014 0.014 -Unc. in length of column / m 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001
Data Processing
Since the volume of the tube is the base area times the height (length) of the column. With the base area kept constant (the radius of the tube), the change in length of the column is directly proportional to the volume of the tube.
Physics Lab – T5
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Keith Chan
The equation of the length of column versus temperature curve is y = 5 10-5x + 0.0112 By subs. y=0 into the equation, we get: 0 = 5 10-5x + 0.0112 x = -224oC Slope of upper limit = Slope of lower limit = 0
0.016 0.012 = 9.30 10-5 84 41
| 9.30 10 -5 0 | △ slope = =4.65 10-5 2
Slope = 5 10-5 5 10-5 moC-1 Unc. of absolute zero
5.0 10 -5 = (1 + ) 224 0.0112 = 225 oC
The calculated value of absolute zero temperature in oC is –224 225 oC The literal value of absolute zero temperature in oC is –237 (3 sig. fig.).
Conclusion
Accuracy
| 223 - (-237) | ] 100% 237 = 94.1%
[1 Precision | 225 | [1 ] 100% | 237 | = 5.06% In this experiment, the calculated absolute zero temperature in oC is –224 225 oC. The accuracy is 94.1% which is pretty high yet the precision is only 5.06% which is extremely low meaning that the uncertainty in the experiment is very high. respectively which is pretty high. However, due to some errors and limitations of the experiment, the calculated lice is affected and shall be discussed in the evaluation
Physics Lab – T5 2
Keith Chan
section.
Evaluation
The extremely low precision means that the calculated values for the absolute zero has great uncertainties suggestion that the calculated value lies in a very large range for it to be accurate. As the changes in length of column is not significant throughout the experiment, it is extremely difficult to construct a best-fit line which passes through most points.
The method used to find out the uncertainty of the slope is very rough and imprecise as the upper and lower limit of slope is very difficult to locate. There is an error when collecting data which lead to inaccuracy and imprecision. 1. The low precision in this experiment is mainly caused by the large least count of the capillary tube which a low responsiveness (i.e. there is no significant observable change for a slight change in substance measuring). This means small changes in volume cannot be measured. During cooling, we had to pump in cold water into the existing hot water to lower the temperature. However, the thermometer is not perfectly sensitive to the
2.
change in temperature meaning a time lag between the lowering of real temperature and the measured temperature. This difference results in an in accurate recording of volume of gas. 3. The temperature of water closer to the flame is higher than 100oC (which also is affected by the atmospheric pressure when the experiment was conducted). Suggestions for improvement 1. Conduct the experiment slowly to ensure the thermometer has enough time to react to the change in temperature.
Physics Lab – T5
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