Courseworks

Physics coursework: Charles’ Law

These are the raw details, which I have taken from my experiment. I need to work out the volume for each measurement taken, as this is the point in my experiment (being in Charles’ law). I am going to work out the volume of the substance under the dyed sulphuric acid. To do this I need to use the ?r2h. I measured the radius to be 0.73mm (of the capillary). I need to turn the height into mm for the equation.Table of volumesTemperature (oC)Equation (uses mm)Av. Volume (mm3)20?*0.73 2*20133630?*0.73 2*20534340?*0.73 2*21035250?*0.73 2*21335760?*0.73 2*21736370?*0.73 2*21936780?*0.73 2*22337390?*0.73 2*226378100?*0.73 2*229383I think the results support my prediction however the last experiment seems to have given greater results than the others. I think this is because the sulphuric acid in the capillary takes a different amount of time to cool down as the thermometer (this suggest longer). I think I should have given it longer to cool down, this however would be hard as I had a limited time unless I did the experiments on different days, which would have aroused many other problems.I measured the results as well as I could but the Ruler I was using only measured to the closest mm, I may not have achieved the difficult task of doing the readings at exactly the right time also, it was hard to watch the thermometer and the ruler at the same time with other equipment (such as clamps) hindering you. This would have been hard to avoid. The thermometer only measures to the closest degree so this may have caused some error. The thermometer although close, wasn’t exactly in the same area of the water as the capillary so they could have experienced different temperatures.To minimise these errors the experiment could be done more times and more time spent on each test. More accurate measurements taken, maybe use of digital or computer equipment to measure temperature and potentially volume. Better heat control so the heat is equally spread across the water, again a computer could achieve this or the use of electrodes or another heat source. I think the largest source of error will be if the thermometer and the substance in the capillary tube cool down at different times this would give strange readings for each time I did the experiment. In terms of in the same experiment the largest source of error I think will be the accuracy of reading the ruler, reading it exactly at the right temperature and being level with it to read it accurately. Room temperatures and pressures would have altered during the experiment; if the experiment took place in a more controlled environment this would be minimal. An enclosed lab instead of a busy one would work better.The ruler was only fixed to the capillary by an elastic band also, this could have caused trouble as it may have moved up or down. A permanent measuring device or a digital one could have helped solve this.I think the accuracy of the measurements will be a big error so I have chosen to use error bars according to how well each measurement instrument reads what it does. In the equation for the volume I use V=?r2h in the radius I used a measuring microscope and this read to the 0.00005m and for the height I used a ruler which measured to 0.0005m, I need to add these together to get error bars for my graph. Since the radius is squared I need to add it twice so I get the calculation 0.00005 + 0.00005 + 0.0005 = ?0.0006mConclusionI think my results are reliable in supporting Charles’ law but in that Temperature is proportional to volume when pressure is constant but my reading for absolute zero is far too low. This means my results are not very good for showing this and overall are not very reliable. I think the problems with my results would have mostly been systematic errors as the proportionality would still be kept the same then yet finding a good value for absolute zero would be hugely effected by these errors.I think that my data has few anomalies and seems reliable but doesn’t show reliability when comparing it to the theory. I think that my results support my prediction in that there will be proportionality between volume and temperature.EvaluatingI think the sources of error were systematic as the results support that Volume is proportional to temperature when pressure is constant. Systematic errors are problems with you plan which would effect every result, random errors are little errors which might happen and would only effect certain results. This suggests that errors affected each of my results suggesting they were systematic.I think my results reliability has to be questioned as the reading for absolute zero is too far out. I think my readings are reliable in showing that volume is proportional to temperature. I think the key sources of error were the equipment. The capillary tube may not have cooled down so the volume was higher in each experiment. I think taking the readings to great accuracy could have been hard as I had to be level with the thermometer and the ruler to take the reading, which I could only take in the short time in which the water was at the right temperature.I think there aren’t any obvious anomalies but if I’d had more time I would have done the whole third experiment again, the readings are too high compared with the others and deviate from the mean too much. I think that the repeats are not close enough to say my results is that reliable. I think all my measurements should be lower.If I were to extend the experiment I would use more reliable equipment (i.e. A better capillary tube) and I would have used thermostatically controlled water baths. I think my results would have been better if I had taken out the experiment more times, maybe I would re-think my method as the problems with it seemed to effect all my results. I think there aren’t too many discrepancies between my data but my results do not support the theory of absolute zero very well.

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