After that, I will empty the cup and with the heatproof mat and lid, I will take the cup to the hot water tank and fill it up to the marked level indicated on the inside of the cup. The starting temperature will probably be around 90 C. (In the case of possible repeats I may be using a slightly different starting temperature.) Immediately after the cup is filled, I will put on the lid to prevent heat and energy loss, take it back to my working bench and insert the thermometer through the hole in the middle of the lid and take the first reading at 0 minutes and start the stop-clock.
I will repeat this method for each cup. I will then be taking a reading every minute after that for a total of 10 minutes for each cup (i.e. 30 readings for all three cups in total). If I decide it is necessary to do repeats for accuracy, averaging results (for an unbiased conclusion) and fair testing then I will be doing 60 readings in total. After I have finished the experiment, I will tidy my apparatus away safely, carefully and neatly.
In this experiment there is no need to wear safety goggles, as I am not dealing with any corrosive substances.
Fair testing:
The following will be kept constant to make the test a fair one:
- The equipment e.g. cups, thermometers and so on, so as to make sure that the conditions, amounts and properties such as temperature are kept the same.
- The room temperature ( C) so excess heat from outside does not affect the rate of energy loss by radiation, conduction or convection.
- The volume of water because we need to keep the heat energy levels the same and different amounts of water will affect factors such as energy loss.
These are our constants.
Our variable is the temperature loss (which cannot be manipulated).
- The starting temperature i.e. for the first reading the starting temperature for all 3 cups will be 92 C and for the repeats (if necessary) it might be for example, 88 C (average being 90 C).
N.B - variables:
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Factors like timing (i.e. when we will take the readings and how long for) are our independent variables – this being the type of factor we will change step-by-step, deliberately.
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Our readings (results) are the dependant variables – the size or amount of this depends on the first reading.
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All of the other variables will be our constants – they will be kept under control.
Obtaining
Preliminary experiments:
For this experiment, my preliminary experiments went exactly according to my planning, method, as did my repeat. Therefore I did not have to change any of my planning or my method, which increases my chances of obtaining accurate results, effectively helping me with more accurate analysing. Also this makes me more confident of the slimmer chance of anomalous results being shown on my graph.
Results:
(All of the above results are in degrees Celsius.)
Average of range: 90.5 C
Range of starting temperature for 1st and 2nd readings: 7 C
Graph(s):
See graph paper.
Observing:
I have noticed, from the graphs (see graph paper) and table (above), that at the beginning, there would be a more dramatic drop in temperature and it would get more gradual towards the end. This is because there was a lot more energy to lose at the beginning so when more was lost to start off with, there was not as much to be lost at the end, so there is less energy lost and so the process of radiation occurs at a slower rate.
There is a poor range in my results, mainly, I think, because my cups were polystyrene and therefore did not let as much heat escape as, say, the plastic cups did, i.e. they were poor radiators. The preliminary experiment was started at 87 C and the repeat was started at 94 C therefore only allowing a range of 7 C. The averages shown in the table were relatively close as well. The graph is slightly unclear as the results are close together as there is not much change of temperature throughout the experiment, so it makes it difficult for a detailed analysis.
I can tell that, evidently, on the graph (although unclear it is readable and relatively reliable), it shows that my prediction was in fact, correct as the painted black polystyrene cup was the best radiator (i.e. lost the most heat/ energy); the polystyrene cup covered in shiny tin foil will be the worst radiator (i.e. stored the most heat/energy) and the plain matt white polystyrene cup will be in between the other two. The rate of heat and energy loss, as I mentioned previously, relies on the type of container the liquid is kept in (e.g. whether it is a thermal container – in this case, a polystyrene or plastic cup were the two options), and what type of surface it has. The latter is more important because, depending on what type of properties the surface of the container has, the rate of heat and energy loss can vary a little or a lot.
Analysing & Concluding
Analysis:
Looking closely at the graphs I can see that there is room for improvement. The graph is not at its most attractive because the lines showing the readings taken are shown relatively close together. Therefore, although I believe the pattern explained in my prediction is evident, it is not entirely clear; therefore a completely accurate analysis will be difficult as not as much information as I had originally hoped for can be extracted from it. However, the temperature drop (even though it is not dramatic i.e. limited range) shows my prediction to be accurate e.g. when the black cup is the best radiator – the line shows a larger drop of temperature then the others.
Visually, the lines look similar in trend and pattern: they start off at the same point and the most dramatic of temperature drops are shown in all three lines near their starting point, then they start to even out and the line’s curve becomes straighter and gradually the line slows to the extent of being virtually straight. This is because the most energy stored in the container is at the beginning when the container has just started to lose some energy. This is a vague indicator of how much energy was stored in comparison to when the line straightens out, implying there is less energy to lose so the process of radiation, conduction or convection is blatantly slowed down. However, we cannot measure how much energy was used, stored or lost, as that was not part of our experiment. When the lines ‘come together’ in the middle of the graph, it means this is when they have around the same amount of energy in the cups after they have exerted the most energy (at the beginning). The lines finish up at slightly different points on the graph e.g. the black cup finishes at 72 C (on the first reading), the cup with tin foil at 74 C and the plain white cups at 73.5 C. This is a difference but there is not a wide range.
This is proof that the cups begin to show that the speed of the process depends or relies on the surface of the container as the surfaces radiate more energy, less energy or energy somewhere in between due to the type of property the surface has e.g. shiny, matt, bright and so on.
Conclusion:
In conclusion I think that the experiment summed up and justified my prediction. My prediction as in ‘Planning’ was ‘that the painted black polystyrene cup will be the best radiator (losing the most heat the quickest), the polystyrene cup covered in aluminium foil will be the poorest radiator and the white polystyrene cup will be in between the other two, because of their surfaces. Also, because I will be using polystyrene cups in my experiment, this will make the container (cup) more insulated.’
The results table and some of my graphs show that the painted black cup finished at 72 C after 10 minutes, the cup covered in aluminium foil at 74 C and the white cup at 73.5 C. Therefore my theory is correct because the cup with aluminium foil finished off at the highest temperature (i.e. storing the most heat) proving it to be a poor radiator; the painted black cup finished at the lowest temperature – 72 C (i.e. losing the most heat) showing it is a good radiator and the plain white cup finished at 73.5 C – a compromise between the other two – showing that although it lost heat, it also had the properties to be able to store heat as well, proving it to be the happy medium of the two.
The graphs show the visual pattern and are all alike in that respect: same starting off point, largest drop near the beginning (the most noticeable curve), the line evening out in the middle (showing the rate of radiation is slowing down) and then finally coming to a halt on a gradually straightening-out line.
This brings me to the conclusion that my results, even though not as good (e.g. in range) as I had hoped for, are satisfactory and are substantial evidence of the rules about the rate of radiation depending on the type of surface its container has and its properties e.g. shiny surfaces are poor radiators: they store heat.
Evaluation
Looking back at my experiment, I am aware there is room for improvement, but I am fairly satisfied with the outcome: a successful experiment with reliable results.
Fair testing?
The experiments on all three cups were conducted safely and efficiently. The apparatus was safe and I used the same equipment for testing all three cups and I tried to keep the atmosphere outside the cups the same. For example, the lights in the room and the hot water supply tank both gave off significant amounts of heat from the energy they used while I was conducting the experiment. Things to even this out like opening the windows, switching off the lights and only switching the tank on when it was needed helped to even the room’s temperature out. I kept the same timing between readings and carried on taking the readings for the same amount of time to make the results accurate and fair and to help plot a reliable graph with as few anomalous results as possible. All around, I think that the experiment was conducted fairly and I am pleased with that.
Accurate and reliable results?
Although on my graphs there are a few anomalous results, I think that this most probably is due to outside conditions, but they did suggest possible faults with factors such as timing and maybe even in the method. However, my results as clearly stated in the results table show that my prediction along with scientific facts proves that the rate of thermal radiation is altered by properties of the different surfaces on various containers. My results do have a poor range (7 C) but I think that effectively this only affects the visibility of change on the graph, not the reliability of my results, as I have not found any problems analysing them.
I cannot see points, which are way away from the line of best fit. Obviously there are some, which are slightly off the line, but none are of a noticeable distance away. This leads me to believe that my results do have a good level of reliability.
As I explained in my conclusion my results and experiment sums up an excellent outcome from the aim (‘to investigate the rate of energy loss in different types of cups by thermal radiation’) which is basically that good radiators have properties like dull/matt, dark and so on and poor radiators have properties such as shiny, bright, for example. My results were good enough for me to be able to plot them on the graph, though. I believe my results have been good enough for me to draw a strong conclusion, as I have been able to justify and back up my conclusion with evidence, scientific facts and results.
I think improvements such as better room conditions and a better range in my results would be good for other such experiments and repeats. Also, repeats could help me draw a better conclusion and a graph, which has a better quality of readability, and could also help me average my results.
The evidence, although at points hard to read (on the graph) showed a pattern, which makes me confident the experiment, was a success: the better radiator, the quicker the liquid (water) cools down.
