Implementation
I have recorded my results in tables and drawn graphs to display the information clearly.
Experiment 1
In these experiments I have tested the effect of different weights on a crunchie with and without chocolate on to see the effect on amount of compression
With Chocolate:
Without Chocolate:
From this experiment it can be derived that the maximum weight before collapsing is around 9kg whether the chocolate is on or off, and the actual compression is very minimal, only around 3mm. So for my future experiments I shall use 2kg weight each time.
Experiment 2
In these experiments I have tested the effect of different surface areas on compression I have left the chocolate on for these experiments.
Analysis
Experiment 1
This investigated the effect of removing the outer coating of chocolate of the crunchie bar. By observing the results that have been displayed in the graph the overall conclusion is that there Is no clear difference in compression. The bar without chocolate compressed slightly easier- requiring less weight. To achieve a compression of 3mm the bar without chocolate needed 60N and the bar with chocolate needed 80N. In both cases the bar did not alter with only 20N of force acting on it. Then as you can see from the graphs there compression to force is constant until 3mm compression then any weight after that just crumbled the bar leaving it without a height just a pile of crumbs.
From this experiment I realised that it is very difficult with the equipment supplied to read the difference in compression after 1kg added so any experiments after this I added 2kg weights at a time, as this produces a larger compression thus easier to read.
Experiment 2
This investigated the effect of surface area on amount of compression. I have not removed the chocolate for this experiment as you can see from experiment that it does not make a noticeable difference.
I used 2 sized pieces for this experiment:
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Bar 1: 20 x 30 x 15mm
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Bar 2: 10 x 10 x 15mm
The second is a much smaller piece in surface area but with the same height.
As you can see from the graphs Bar 1 with stood a much higher weight than Bar 2, it took 140N to crumble the larger piece and only 80N for Bar 2. The other main difference is that it took 60N of force to impact any measurable compression on Bar 1 at which was only 0.25mm hardly measurable, compared to Bar 2 that took 20N to receive a 0.5mm compression. Theses facts clearly state that a larger surface area has a much stronger structure where as a small one is weaker. Another interesting difference with Bar 1 is that it only compressed 1.1mm overall and then crumbled before any more compression. Bar 2 also did not withstand a large compression to former pieces, only 1.5mm before crushing.
Experiment 3
This investigated the effect of height to compression. I used 2 bars in the experiment
Bar 1: 20 x 20 x 30mm
Bar 2: 20 x 20 x 15mm
The first bar is twice as high, by looking at the graphs they immediately look very similar height does not look to effect compression they both start to compress at around 20N and then crumble after 6mm and 7mm compression. But after a closer inspection Bar 1 seems to be very inaccurate, it Is actually the same test as in experiment 1 but I have obtained very different results, the graph steepness are the same but I have used a much smaller scale in this experiment so theoretically it is actually much steeper which clearly shows different results. I believe there to be a mistake within my results in this experiment as the former graph makes more sense, all other results have proven to be constant compression with constant Force –straight line graph, where as Bar 1 in this experiment is regular until 80N where it suddenly increases from 2mm compression under 60N to 6mm compression under 80N which disagrees with all former experiments. So my result for 80N must be anomalous I have circled it on the graph to show that it is not correct. Bar 2 however is correct the Bar reacted as formally thought. Its compression is doubled for each weight. Compared to the bar in experiment 1 its overall compression is 7mm compared to 3mm and withstood a weight of 140N compared to 80N (double again) so it would seem as if the material has a compression rate per height and this will increase with height.
Evaluation
- The first obvious conclusion to state is the fact the compression increases with Force all the experiments shows this.
Ex 1: Bar 1 Bar 2
20N – 0mm 20N – 0mm
80N – 3mm 80N – 3mm
Ex 2: Bar 1 Bar 2
20N – 0mm 20N – 0.5mm
120N – 1.1mm 60N – 1.5mm
Clearly as shown above every bar compressed further with a higher fore acting on it.
- From Experiment 1 I can also conclude that an outer layer (this example chocolate) does not affect the amount of compression of a material within. My results altered slightly for a bar without chocolate which was quicker compression with a smaller force but the difference is so minimal that it is hardly possible to conclude a difference.
- From Experiment 2 it can be derived that a larger surface area compresses less, Bar 1 the larger surface area of the two, compressed nearly half as much as the half sized piece and withstood double the amount of force than the smaller piece, this is due to the force being equally spread across the structure whereas with a smaller piece there are much less honey comb (walls-in effect) to deal the force hence why it crumbles quicker but the larger piece has much more honey comb structure to deal with the force. So if for example each length of material within the crunchie has an equal force expressed on it if there are more pieces then there will be less force exerted onto each one so it will not break as easily.
- From Experiment 3 is can be clearly seen that a piece of material (in this case crunchie bar) compresses more the higher the piece. I used a piece twice as high and within a small amount of error all of its properties were doubled which proves this. This means that the crunchie must have a compression per height so the larger the height the more it will compress.
Conclusions
I think overall my results were definitely accurate enough to draw firm conclusions that are correct. All my experiments relative to one another reacted in the same
- Did not compress under a small weight
- Constant compression per force exerted
- At a certain force relative to the experiment the piece crumbled
There were a few problems with my experiment that make it inaccurate and if I were to further this investigation or repeat it again then I would try and improve these factors:
- Try to use a material that is 100% constant throughout because the bars did vary in aeration (different densities) and chocolate thickness varied considerably per bar. The chocolate on the bar also if got too hot started to melt in which case varied in properties. The experiment also took a couple of days to complete and all the bars were opened on the first session this may have effected the properties of the honey comb centre and in which its compression rate.
- The equipment used to measure the bars with was also not of perfect accuracy; Micrometer and vernier calliper. The micrometer was of better accuracy but a lot of the time after a compression of weight the chrunchie would slightly chip or have dents where pieces crumbled within, so an overall measurement would have to be taken, The vernier calliper only had a thin measuring section so when was pushed onto the bar to get an accurate measurement it would cut into the chocolate especially when it was hot therefore increasing the compression unfairly. As the experiment was done over a couple of days equipment was lost track of and different pieces used so any error would not be continues throughout but effect the results also unfairly.
- The equipment used was only accurate to 1dp using human judgement, which is not 100% reliable a lot of the time compression was such a small amount readings to an extent would have to be guessed, if the reading was taken at a slight angle then with this equipment would change the result due to lack of time some of the readings were rushed and so this mistake may have been made.
Ways to improve:
- Use a material such as a high quality sponge that had equal aeration throughout and then aeration differences could also be investigated. The material would also have to be quite durable so that was not effected by handling – a resistant outer shell.
- Use high tech computerised equipment accurate to 2dp or more maybe a computer program to record results and draw graphs so these would be clearer. This would lessen the possibility of human error as in experiment 3.